Here is the new and improved version of my article about allergy testing and treatment. I think it is much more readable and easy to use in this format.
The series of posts linked here covers some of the current problems and issues with testing, doctors and scientific studies. It is applicable to all allergies, not just corn allergy. I will continue to update and add to it.
I hope the information is helpful. Please feel free to send others the links or print out the posts to help educate doctors and others about allergies.
Much labor went into this work. I would prefer that you link rather than reposting the entire series. If you post excerpts elsewhere, please do provide credit to me and a link to the post(s) on my blog.
Showing posts with label allergy testing. Show all posts
Showing posts with label allergy testing. Show all posts
Tuesday, January 02, 2007
Monday, December 04, 2006
Problems with Allergy Diagnosis
[This article is cross-posted at The Purple Puzzle Place]
NHS Blog Doctor's contribution to this edition of the Pediatric Grand Rounds is about cow's milk allergy and formula marketing. While NHS Blog Doctor makes some good points, the post brought out some things to which I've been giving considerable thought.
NHS Blog Doctor's contribution to PGR is about cow's milk allergy and formula marketing. While NHS Blog Doctor makes some good points, the post brought out some things to which I've been giving considerable thought.
One is illustrated by a statement from The British Dietic Association that NHS BlogDoc linked to. It says, "The only reliable way to test for a true allergy is an IgE blood test, a skin prick test or a patch test."
That's a common misconception among doctors and even allergists. The scientific community largely agrees that none of those tests are really all that accurate. Skin prick tests are generally considered to be the most reliable, but even those have only somewhere between a 50% and a 90% accuracy.
Variables such as the tools used, how the test is performed, medications taken by the patient, how recently the person has been exposed to the allergen, recent anaphylactic events, and even the age and quality of allergen samples used in testing can affect the reliability of testing.
Many scientists seem to believe that commercial allergen extracts are less effective and reliable in allergy skin-prick testing than a prick-to-prick method (poking the actual food and then the person's arm), especially with fruit.
Incidentally, some experts point out that "false positives" are not really false positives in that they do reliably indicate the presence of IgE antibodies to that substance. In some cases a person may have antibodies with no discernable clinical reaction; in others this could be an indication that the person may develop a more serious allergy with continued exposure to that item.
Test results can provide useful information, but clinical symptoms trump testing.
#############
An elimination diet (taking out a food to see if symptoms subside, and then reintroducing it to see if they return) can be used with some reliability to diagnose adverse food reactions, and is often used in conjunction with other testing to confirm results.
The gold standard for diagnosing allergies is a double-blind oral challenge, giving the person something (when neither the doctor nor the patient knows whether it's the food or a placebo) and seeing how they react. If the person has an onset of symptoms consistent with allergies after consuming the food, they can be considered allergic no matter what the test says.
Anaphylaxis that is clearly the result of consuming a particular food requires no other testing, and a skin prick or oral challenge in that case can be far too dangerous. Even with the small possibility that the food in question wasn't actually the cause of the anaphylactic reaction, consuming the food usually carries too much of a risk to take that chance. Blood testing can still be used to help confirm the diagnosis if desired.
Unfortunately, too many doctors and allergists believe the hype about allergy testing. Far too many interact with their patients based on statistics rather than on that person's individual history, and assume that if something is rare then it must not be present in their patient.
When confronted with a patient who has an anaphylactic reaction or consistent allergic symptoms when consuming a particular food, but has a negative result to the allergy-testing, too many doctors will tell the patient that they don't truly have an allergy.
If a doctor insists that the allergy test must be right and the patient should go ahead and eat corn despite clinical symptoms of allergy, the patient could land in the emergency room or the morgue.
I know of someone who "forgets to breathe" when she is exposed to popcorn fumes, along with other symptoms of anaphylaxis, had huge welts on the skin prick test, and yet still has trouble getting doctors to take her allergies seriously.
She says, "Think about this. I have the highest weal scores possible, confirmed reaction to at least one corn product (popcorn) through an ER visit, and yet, I cannot get the majority of the medical community to take me seriously. Is it any wonder others have issues?"
This allergy sufferer took part in a study about the prevalence of corn allergy. It was the Tulane study that's often quoted as the only definitive measure of the prevalence of corn allergy. My understanding is that the study was funded by corn companies.
All of the participants had positive skin prick tests and a clinical history of adverse reactions to corn. Of 22 people that fit their research criteria and agreed to participate, 3 were excluded from the study because of negative skin test results just prior to the test. Of the 19 remaining, 2 did not complete the challenge (perhaps because of the severity of their reactions?).
The researchers defined "allergic reaction" so tightly that they defined many clear typical allergic reactions right out of the study by requiring that the reactions be objectively observable.
"If no objective reactions were observed at the end of the DBPCFC, open challenges were done with corn chips followed by popcorn. Subjects without reactions were considered negative."
Only about 6 or 7 of the 16 common symptoms of moderate to severe allergic reactions listed on Medline would have qualified under their standards. After all, itching, dizziness, difficulty swallowing, chest tightness, nausea and abdominal pain are not empirically observable or quantifiable. Airway restriction was counted only if it resulted in more than a 15% decrease in peak airflow. Vomiting, diarrhea, and congestion were, according to information from a participant, not considered a reaction.
The study summary says [definitions in brackets added by me]: "Five patients had positive challenges, two during the blinded portion, three with the open challenge. Reactions included: anaphylaxis, urticaria [hives], conjunctivitis [redness of the eyes] and rhinorrhea [runny nose], perioral urticaria [rash on the face or mouth area] and edema [swelling], and wheezing (>15% decrease in peak flow)."
Several of the ingredients in the study's placebo were also foods that often contain hidden corn (sugar often contains corn syrup, apple sauce and apple juice almost always contain corn-derived citric acid and/or corn-derived sweeteners, etc.), so I wonder if the placebo was truly a good control.
The person I know who took part in the study claims that she started vomiting within moments of the first administration of the test product, and the researchers considered that a non-reaction and continued the test. She spent the rest of the night huddled into a ball, crying from abdominal pain and having severe diarrhea and gastrointestinal distress. She got immediate mucous and congestion in her airways and sinuses as well. Because of her history of anaphylaxis when exposed to popcorn fumes, she did not take the risk of participating in the open popcorn challenge.
The participant was categorized in the "no reaction" portion of the study results.
Vomiting and diarrhea are known, widely-accepted symptoms of anaphylactic allergic reaction, and yet these researchers and many doctors (including my own allergist) discount them as allergic symptoms.
This participant said, "As a matter of fact, the nurse said I was definitely highly 'atopic' but was considered not reactive by their standard. Um... atopy is allergy."
If this is the kind of research we have, how accurate do you suppose the figures of allergy prevalence based on such studies (1-2% of adults, 6-8% of children) really are?
Unfortunately the attitude from doctors that allergic reactions aren't real because they're uncommon, don't fit into a certain tightly-defined set of symptoms (usually limited to athsma, hives and airway restriction), or are unverified by a particular test, is all too common.
I've experienced this attitude personally.
My allergist believes that because it's rare for a child to have more than 4 food allergies, some of her positive skin tests confirmed by clinical observations must be "false positives", because she can't possibly really be allergic to that many foods.
Our allergist insists that many of my daughter's and my adverse reactions to specific foods must be "coincidence" and refuses to consider even the possibility of an intolerance, much less an allergy. Those reactions include swelling and itching of the mouth and throat, all-over body itching, excema, rashes (but not the magical giant hives), severe immediate vomiting and/or diarrhea, and other reactions happening consistently after the food is consumed.
Our allergist believes that because Baby E's positive skin test welts were "not that big" that she obviously "isn't very allergic" to any of the foods she tested positive to. He says that despite the clinical evidence of a severe, immediate reaction (sometimes bordering on anaphylaxis) to the smallest trace of any corn or soy derivative. He has encouraged me to go ahead and give my child things with corn and soy derivatives in them, and was not willing to try to find an allergy medicine that doesn't contain corn or soy for her.
He must not be aware of the research and clinical evidence indicating that the size of the wheal is not directly correlated to the severity of the reaction, and that allergic reactions can take place even with a completely negative skin test. A person can have a very small wheal with a severe anaphylactic reaction to that food.
Also, it is common knowledge that "the wheal size induced by both positive control solutions and allergen-induced prick tests tend to be smaller in infants than adults." Young children are also known to have a higher number of false negatives than adults.
I was told that I wasn't allergic to any foods because none of my welts reached 6/12. I had a positive result of 3/9 to the control, which meant that none of my 5/7 or 4/10 welts "counted" as positive results--despite a clinical history of adverse reactions to those foods which meant I hadn't consumed some of them for a year or more.
Interestingly enough, the control and/or the carrier used in allergy testing often contains glycerine--a substance often derived from common allergens such as coconut, corn, soy or any number of oils derived from vegetable, animal or petroleum sources.
Several studies have found that a glycerine-containing control has a different rate of positive reactions than saline alone.
There are documented cases of allergy to saline solution, glycerine, and the preservatives (especially thimerosol) in saline solution.
Allergies to "glycerine" are noted repeatedly both in anecdotes gleaned in a quick web search, and in scientific literature. Glycerin can cause allergic reactions all on its own.
Strangely enough, I could find little if any mention of trying to differentiate between sources of glycerine when an allergic reaction is confirmed. Saying someone is "allergic to glycerine" without looking at the food from which the glycerine is derived is like saying someone is "allergic to oil" because they had a reaction to peanut oil.
My positive reaction to the control was clearly not the result of dermographism, because other pricks registered 0 and I don't get a raised welt from being poked with a bare needle.
There is no protocol in place for distinguishing between dermographism, a false positive for other reasons, and an actual allergic reaction to the negative control in allergy skin testing. It would be so simple and inexpensive to rule out dermographism in such cases just by adding a prick with no substance or with purified water to the test. I don't know why that's not standard procedure.
I think we can all agree that any positive reaction to the negative control makes interpreting test results difficult if not impossible. Yet a common standard is "3 mm larger than the negative control" for a positive result. Many allergists don't take into account that the control should be at or very close to 0 for results to be reliable, despite the fact that dermographism is considered by some to be a contraindication to skin testing.
Apparently there is some precedence in the scientific community for using the smallest wheal as the control if the saline or glycerine control has a larger wheal than one or more of the allergens being tested: "If the wheal reaction to the glycerin control was greater than the wheal diameter of the allergen reaction, the wheal size for that allergen was set to zero."
Even with a negative control, the statistics I've seen for reliablility of skin prick testing range from 50% to 90% accuracy. Most sources agree that the other methods of testing are even less accurate.
Yet what are the remaining 10% to 50% of patients to do when their doctor believes that testing is the only accurate way to diagnose allergy?
They find themselves in situations like my recent experience: I had a clear anaphylactic reaction to a particular food after multiple occasions of less severe but increasingly obvious allergic reactions to that food.
Within seconds of ingesting the food I had severe itching and tingling of the mouth and throat, all-over body itching, tightness of the throat, difficulty swallowing, hoarseness and coughing, among other symptoms also including dizziness, rapid heartbeat, swelling eyelids and immediate intestinal distress.
Benadryl helped significantly within about 10 minutes of the dose, suggesting that the reaction was histamine-related.
Perhaps because months earlier I had tested "negative" to that food (the welt was only 4/7), my allergist didn't seem to believe I could really be allergic to that food. He wouldn't even see me about the reaction, although he could call in a prescription for an epi-pen "if I really wanted him to, even though he didn't think it was necessary."
He added that if I wanted to, we could do a skin-prick test at some point in the unspecified future "to see if I was really allergic to it."
I suspect that if the skin test came back negative, he would tell me to go ahead and eat it.
If I ever went back to see him again, that is.
NHS Blog Doctor's contribution to this edition of the Pediatric Grand Rounds is about cow's milk allergy and formula marketing. While NHS Blog Doctor makes some good points, the post brought out some things to which I've been giving considerable thought.
NHS Blog Doctor's contribution to PGR is about cow's milk allergy and formula marketing. While NHS Blog Doctor makes some good points, the post brought out some things to which I've been giving considerable thought.
One is illustrated by a statement from The British Dietic Association that NHS BlogDoc linked to. It says, "The only reliable way to test for a true allergy is an IgE blood test, a skin prick test or a patch test."
That's a common misconception among doctors and even allergists. The scientific community largely agrees that none of those tests are really all that accurate. Skin prick tests are generally considered to be the most reliable, but even those have only somewhere between a 50% and a 90% accuracy.
Variables such as the tools used, how the test is performed, medications taken by the patient, how recently the person has been exposed to the allergen, recent anaphylactic events, and even the age and quality of allergen samples used in testing can affect the reliability of testing.
Many scientists seem to believe that commercial allergen extracts are less effective and reliable in allergy skin-prick testing than a prick-to-prick method (poking the actual food and then the person's arm), especially with fruit.
Incidentally, some experts point out that "false positives" are not really false positives in that they do reliably indicate the presence of IgE antibodies to that substance. In some cases a person may have antibodies with no discernable clinical reaction; in others this could be an indication that the person may develop a more serious allergy with continued exposure to that item.
Test results can provide useful information, but clinical symptoms trump testing.
#############
An elimination diet (taking out a food to see if symptoms subside, and then reintroducing it to see if they return) can be used with some reliability to diagnose adverse food reactions, and is often used in conjunction with other testing to confirm results.
The gold standard for diagnosing allergies is a double-blind oral challenge, giving the person something (when neither the doctor nor the patient knows whether it's the food or a placebo) and seeing how they react. If the person has an onset of symptoms consistent with allergies after consuming the food, they can be considered allergic no matter what the test says.
Anaphylaxis that is clearly the result of consuming a particular food requires no other testing, and a skin prick or oral challenge in that case can be far too dangerous. Even with the small possibility that the food in question wasn't actually the cause of the anaphylactic reaction, consuming the food usually carries too much of a risk to take that chance. Blood testing can still be used to help confirm the diagnosis if desired.
Unfortunately, too many doctors and allergists believe the hype about allergy testing. Far too many interact with their patients based on statistics rather than on that person's individual history, and assume that if something is rare then it must not be present in their patient.
When confronted with a patient who has an anaphylactic reaction or consistent allergic symptoms when consuming a particular food, but has a negative result to the allergy-testing, too many doctors will tell the patient that they don't truly have an allergy.
If a doctor insists that the allergy test must be right and the patient should go ahead and eat corn despite clinical symptoms of allergy, the patient could land in the emergency room or the morgue.
I know of someone who "forgets to breathe" when she is exposed to popcorn fumes, along with other symptoms of anaphylaxis, had huge welts on the skin prick test, and yet still has trouble getting doctors to take her allergies seriously.
She says, "Think about this. I have the highest weal scores possible, confirmed reaction to at least one corn product (popcorn) through an ER visit, and yet, I cannot get the majority of the medical community to take me seriously. Is it any wonder others have issues?"
This allergy sufferer took part in a study about the prevalence of corn allergy. It was the Tulane study that's often quoted as the only definitive measure of the prevalence of corn allergy. My understanding is that the study was funded by corn companies.
All of the participants had positive skin prick tests and a clinical history of adverse reactions to corn. Of 22 people that fit their research criteria and agreed to participate, 3 were excluded from the study because of negative skin test results just prior to the test. Of the 19 remaining, 2 did not complete the challenge (perhaps because of the severity of their reactions?).
The researchers defined "allergic reaction" so tightly that they defined many clear typical allergic reactions right out of the study by requiring that the reactions be objectively observable.
"If no objective reactions were observed at the end of the DBPCFC, open challenges were done with corn chips followed by popcorn. Subjects without reactions were considered negative."
Only about 6 or 7 of the 16 common symptoms of moderate to severe allergic reactions listed on Medline would have qualified under their standards. After all, itching, dizziness, difficulty swallowing, chest tightness, nausea and abdominal pain are not empirically observable or quantifiable. Airway restriction was counted only if it resulted in more than a 15% decrease in peak airflow. Vomiting, diarrhea, and congestion were, according to information from a participant, not considered a reaction.
The study summary says [definitions in brackets added by me]: "Five patients had positive challenges, two during the blinded portion, three with the open challenge. Reactions included: anaphylaxis, urticaria [hives], conjunctivitis [redness of the eyes] and rhinorrhea [runny nose], perioral urticaria [rash on the face or mouth area] and edema [swelling], and wheezing (>15% decrease in peak flow)."
Several of the ingredients in the study's placebo were also foods that often contain hidden corn (sugar often contains corn syrup, apple sauce and apple juice almost always contain corn-derived citric acid and/or corn-derived sweeteners, etc.), so I wonder if the placebo was truly a good control.
The person I know who took part in the study claims that she started vomiting within moments of the first administration of the test product, and the researchers considered that a non-reaction and continued the test. She spent the rest of the night huddled into a ball, crying from abdominal pain and having severe diarrhea and gastrointestinal distress. She got immediate mucous and congestion in her airways and sinuses as well. Because of her history of anaphylaxis when exposed to popcorn fumes, she did not take the risk of participating in the open popcorn challenge.
The participant was categorized in the "no reaction" portion of the study results.
Vomiting and diarrhea are known, widely-accepted symptoms of anaphylactic allergic reaction, and yet these researchers and many doctors (including my own allergist) discount them as allergic symptoms.
This participant said, "As a matter of fact, the nurse said I was definitely highly 'atopic' but was considered not reactive by their standard. Um... atopy is allergy."
If this is the kind of research we have, how accurate do you suppose the figures of allergy prevalence based on such studies (1-2% of adults, 6-8% of children) really are?
Unfortunately the attitude from doctors that allergic reactions aren't real because they're uncommon, don't fit into a certain tightly-defined set of symptoms (usually limited to athsma, hives and airway restriction), or are unverified by a particular test, is all too common.
I've experienced this attitude personally.
My allergist believes that because it's rare for a child to have more than 4 food allergies, some of her positive skin tests confirmed by clinical observations must be "false positives", because she can't possibly really be allergic to that many foods.
Our allergist insists that many of my daughter's and my adverse reactions to specific foods must be "coincidence" and refuses to consider even the possibility of an intolerance, much less an allergy. Those reactions include swelling and itching of the mouth and throat, all-over body itching, excema, rashes (but not the magical giant hives), severe immediate vomiting and/or diarrhea, and other reactions happening consistently after the food is consumed.
Our allergist believes that because Baby E's positive skin test welts were "not that big" that she obviously "isn't very allergic" to any of the foods she tested positive to. He says that despite the clinical evidence of a severe, immediate reaction (sometimes bordering on anaphylaxis) to the smallest trace of any corn or soy derivative. He has encouraged me to go ahead and give my child things with corn and soy derivatives in them, and was not willing to try to find an allergy medicine that doesn't contain corn or soy for her.
He must not be aware of the research and clinical evidence indicating that the size of the wheal is not directly correlated to the severity of the reaction, and that allergic reactions can take place even with a completely negative skin test. A person can have a very small wheal with a severe anaphylactic reaction to that food.
Also, it is common knowledge that "the wheal size induced by both positive control solutions and allergen-induced prick tests tend to be smaller in infants than adults." Young children are also known to have a higher number of false negatives than adults.
I was told that I wasn't allergic to any foods because none of my welts reached 6/12. I had a positive result of 3/9 to the control, which meant that none of my 5/7 or 4/10 welts "counted" as positive results--despite a clinical history of adverse reactions to those foods which meant I hadn't consumed some of them for a year or more.
Interestingly enough, the control and/or the carrier used in allergy testing often contains glycerine--a substance often derived from common allergens such as coconut, corn, soy or any number of oils derived from vegetable, animal or petroleum sources.
Several studies have found that a glycerine-containing control has a different rate of positive reactions than saline alone.
There are documented cases of allergy to saline solution, glycerine, and the preservatives (especially thimerosol) in saline solution.
Allergies to "glycerine" are noted repeatedly both in anecdotes gleaned in a quick web search, and in scientific literature. Glycerin can cause allergic reactions all on its own.
Strangely enough, I could find little if any mention of trying to differentiate between sources of glycerine when an allergic reaction is confirmed. Saying someone is "allergic to glycerine" without looking at the food from which the glycerine is derived is like saying someone is "allergic to oil" because they had a reaction to peanut oil.
My positive reaction to the control was clearly not the result of dermographism, because other pricks registered 0 and I don't get a raised welt from being poked with a bare needle.
There is no protocol in place for distinguishing between dermographism, a false positive for other reasons, and an actual allergic reaction to the negative control in allergy skin testing. It would be so simple and inexpensive to rule out dermographism in such cases just by adding a prick with no substance or with purified water to the test. I don't know why that's not standard procedure.
I think we can all agree that any positive reaction to the negative control makes interpreting test results difficult if not impossible. Yet a common standard is "3 mm larger than the negative control" for a positive result. Many allergists don't take into account that the control should be at or very close to 0 for results to be reliable, despite the fact that dermographism is considered by some to be a contraindication to skin testing.
Apparently there is some precedence in the scientific community for using the smallest wheal as the control if the saline or glycerine control has a larger wheal than one or more of the allergens being tested: "If the wheal reaction to the glycerin control was greater than the wheal diameter of the allergen reaction, the wheal size for that allergen was set to zero."
Even with a negative control, the statistics I've seen for reliablility of skin prick testing range from 50% to 90% accuracy. Most sources agree that the other methods of testing are even less accurate.
Yet what are the remaining 10% to 50% of patients to do when their doctor believes that testing is the only accurate way to diagnose allergy?
They find themselves in situations like my recent experience: I had a clear anaphylactic reaction to a particular food after multiple occasions of less severe but increasingly obvious allergic reactions to that food.
Within seconds of ingesting the food I had severe itching and tingling of the mouth and throat, all-over body itching, tightness of the throat, difficulty swallowing, hoarseness and coughing, among other symptoms also including dizziness, rapid heartbeat, swelling eyelids and immediate intestinal distress.
Benadryl helped significantly within about 10 minutes of the dose, suggesting that the reaction was histamine-related.
Perhaps because months earlier I had tested "negative" to that food (the welt was only 4/7), my allergist didn't seem to believe I could really be allergic to that food. He wouldn't even see me about the reaction, although he could call in a prescription for an epi-pen "if I really wanted him to, even though he didn't think it was necessary."
He added that if I wanted to, we could do a skin-prick test at some point in the unspecified future "to see if I was really allergic to it."
I suspect that if the skin test came back negative, he would tell me to go ahead and eat it.
If I ever went back to see him again, that is.
Saturday, November 11, 2006
Corn Allergy or Corn Intolerance?
Do you have a Corn (Maize) Allergy or a Corn (Maize) Intolerance?
Confused? Well so are we.
Actually I think the entire world is confused. The more I read up on this subject in order to shed some light on this confusing debate, the more confused I became. So don't worry, you're not alone in the head scratching.
It seems that when it comes to food intolerance, no one can agree on specifics. About the only agreement is this:
For it to be a food allergy, the immune system (IgE) is involved. Food intolerance the immune system isn't involved.
However that's about where the agreement separates. Some sites will tell you that if your food allergy doesn't show up on tests, then it has to be a food intolerance. We tend to disagree.
How reliable are Corn Allergy tests?
According to a study from March 2004, posted on Allergy Advisor.com "Traditionally, skin-specific and serum-specific IgE tests to maize are used to diagnose maize allergy. It is generally assumed that a negative result indicates the absence of maize allergy. However, it was recently shown that a negative skin-specific IgE and serum-specific IgE to maize flour had no clinical significance for most of the patients studied, and that food allergy to maize has to be proved by double-blind placebo-controlled food challenge studies"
The same study also states: "Many allergens have been isolated from maize, but the majority of them have not been clinically evaluated for their allergenic potential."
Even the Corn Refiner's Association admits: "Though allergens in other food systems have been well characterized, very little work has been devoted to identifying allergens in corn or corn ingredients."
So for starters, the tests are not accurate measures of IgE responses to corn, probably because the allergens in corn have not been fully identified to even make an accurate test for corn. Clearly for diagnosing a corn allergy, testing alone is not going to be an accurate measure of an IgE mediated food allergy reaction. (Despite what your allergist may tell you)
How can you tell if its a Corn Allergy or a Corn Intolerance? What is the difference?
One difference between a food allergy and a food intolerance is portions. A person with a food allergy usually cannot tolerate any amount of that allergen; however a person with a food intolerance can usually tolerate a small portion of an offending food but a larger portion will cause problems. Tolerances on this will differ from person to person whether they have a food allergy or intolerance.
The main difference however is the involvement of the immune system. Despite some sites claims to the contrary, there are a few symptoms which signify the immune system is getting involved. If you have any of the following, you most likely have a food allergy and should see your doctor immediately (you will want to get a script so you can have an Epipen handy).
These are:
Hives, urticaria, skin rash, eczema, - Skin may become red or flushed, raised bumps, itching, or fluid filled blisters.
Itching/burning around the mouth (or other contact area) usually accompanied with swelling.
Labored breathing, tightness of the chest, wheezing, asthma, shortness of breath.
Life-Threatening anaphylaxis.
Skin Contact reactions.
This is not an all inclusive list of food allergy reactions but these generally are not present with food intolerances and only present when the immune system is getting involved. (however there are always exceptions)
I should probably clarify here that when I say "immune system is involved" or maybe I should state that when 99% of the medical field states the "immune system is involved" they are referring only to the IgE immune response.
The immune system has many little warriors out there battling diseases and bacteria on our behalf. Some are IgA, IgG, IgM, IgD, and of course IgE. However, IgE is about the only one that has been even close to thoroughly researched and is the only immune response considered when declaring a food allergy.
IgG has also been proven to have reactions to foods; however these reactions are considered minor and temporary. Thus in medical circles, IgG mediated food allergies are considered intolerances despite the immune systems involvement. It is believed that if you avoid an IgG allergen long enough that the body will stop reacting to it. This is not true of an IgE allergy.
Genova Diagnostics explains the differences between IgE and IgG pretty simply:
IgE Mediated Allergies
Immediate onset (within minutes)
Circulating half life of 1-2 days
Permanent allergies
Stimulates histamine release
Includes foods, inhalants & molds
IgG Mediated Allergies
Delayed onset (4-72 hours)
Circulating half life of 21 days
Temporary allergies
Stimulates histamine release
Includes foods, herbs & spices
This is generally considered the differences between IgE and IgG allergies. Yet, an article by the University of South Carolina School of Medicine gives more time for IgE mediated responses:
"Type I hypersensitivity is also known as immediate or anaphylactic hypersensitivity. The reaction may involve skin (urticaria and eczema), eyes (conjunctivitis), nasopharynx (rhinorrhea, rhinitis), bronchopulmonary tissues (asthma) and gastrointestinal tract (gastroenteritis). The reaction may cause a range of symptoms from minor inconvenience to death. The reaction usually takes 15 - 30 minutes from the time of exposure to the antigen, although sometimes it may have a delayed onset (10 - 12 hours). Immediate hypersensitivity is mediated by IgE." - U of South Carolina, School of Medicine
So if your reactions to foods are more than minutes but less than hours, your chances are pretty good that its IgE mediated and would be considered an actual food allergy. Keep in mind, that though IgG mediated food allergies involve the immune system, the medical community still considers them “intolerances”.
What is a Food Intolerance (Corn Intolerance)?
Food Reactions.org and WebMD both give pretty clear cut and accurate definitions of real food intolerance.
Food Reactions.org states: "Food Intolerance is the inability to completely break down food into absorbable components due to lack or insufficient amounts of digestive enzymes. The unabsorbed food which remain in the digestive system causes the classic symptoms of bloating and cramps and others."
and
WebMD states: "Food intolerance is a digestive system response rather than an immune system response. It occurs when something in a food irritates a person's digestive system or when a person is unable to properly digest or breakdown, the food. Intolerance to lactose, which is found in milk and other dairy products, is the most common food intolerance."
Rules about food intolerance seem to be breaking down in recent years. These two definitions are more conservative than what some sites will tell you, as the discovery of IgG mediated food allergies (intolerances) has made some alter their definitions of food intolerance which I believe is misleading. (one such definition can be found at Australian Disability Online which lists asthma and other histamine type responses as a symptom of food intolerance.)
Food Intolerance symptoms should be mostly harmless, though when you're suffering through it you might wish it wasn't as these can be quite painful and debilitating. These symptoms include: (be aware these can also be present if it’s a food allergy)
Nausea
Bloating
Abdominal Pain
Diarrhea
These symptoms may start about a half hour after eating or drinking the problematic food, but they may also be delayed.
Rules of Thumb on differences between Corn Allergy and Corn Intolerance:
1. Immediate (minutes - Corn Allergy) vs. delayed reactions (hours - Corn Intolerance).
2. Immune system involvement: Hives (skin irritation), stuffy nose, chest congestion, swelling, anaphylaxis. (Food intolerance is mainly digestion issues.)
3. Skin contact problems - skin contact reactions have nothing to do with digestion and are only mediated by the immune system (except harmful chemicals which harm anyone’s skin). If you break out (eczema and acne included), have difficulty breathing, swelling, nausea, etc. by skin contact with a food item, you are most likely allergic to it (or something in it).
Important to note: The body can mask allergy symptoms as a way of survival. So some of these symptoms may not be noticeably present at first, or may not seem to be linked to a particular food. Masked allergies to foods are often present in persons with other skin (eczema and acne) conditions, airborne allergies, mood & behavioral issues, dark under eyes, sleep problems, and other miscellaneous conditions. (See Women to Women: Food Allergy Symptoms for more clues as to conditions which may be caused by hidden food allergies)
Telling the difference between an allergy and intolerance isn't always easy, but your family history will help. According to statistics on Australian Disability Online "Children who have one family member with asthma or eczema have a 20-40 per cent higher risk of developing allergy; if there are two or more family members with allergies then the risk increases to 50-80 per cent." Since asthma and eczema are often symptoms of allergic reactions themselves, its possible that the genetic allergy risk may be even higher than stated.
A full list of food allergy symptoms would be very long and there will be a separate article hopefully fully encompassing any and all symptoms you may experience. However in the meantime, Women to Women has an article which gives the most comprehensive list of systems. Keep in mind, that a food allergy can have all the same symptoms of a food intolerance (digestion issues), but a food intolerance will not have the symptoms of a food allergy (aka immune system response symptoms as explained earlier).
Where to start looking for Food Allergies?
If you just read through the last several paragraphs and you think you might have a food allergy but you don't know where to start, here are a few clues.
There are often two ways people react to allergy foods. They either love them (food allergy addiction) or they hate them. If there is a food you dislike (or strongly disliked as a small child), its possible that a food allergy may be the culprit. Keep in mind that this is not always accurate as the older you get the more memories you have about food, and you may stop liking foods based on non-food related memories. Aka you don't like orange jello because you associate it with the time you had that violent flu.
For parents of young children: Despite what some doctors and parenting advisors might say, young children (babies included) often refuse a food that they know is bad for them or has previously caused them problems. This can also include breast milk if the mother is eating a food to which the child is allergic. Children as they grow older may get finicky and like or dislike foods for other reasons, but pay attention to foods your child is refusing. Keep a list, including brand names as some brands may have added ingredients that others do not. This will help you narrow down possible food allergies. FYI: Enriched products (milks, flours) often have added corn and soy as carriers for the added vitamins.
According to FAAN, common food allergens are: Milk, Eggs, Peanut/Soy, Wheat (other related grains), Tree Nuts, Fish, Shellfish. The FDA only recognizes these 8 allergens to be serious enough to require labeling. FAAN does not recognize corn (nor does most of the USA) and you'll find many doctors will actually discourage a corn allergy even if the test results are positive. Corn Allergy and Intolerance is on the rise. If you do test positive to corn at all (in any even slight amount) you should investigate it through diet. Avoidance and retrial, is the only accurate way to know if it’s going to be a real issue.
Food Allergy Addiction is also something for which to watch out. It sounds funny or like a "fat persons" disease, but it isn't necessarily. Physiologically, the body becomes dependant (addicted) to the allergens presence and starts a craving for it. There are several theories for this (see below links) which center more on the chemical reaction that happens in the body when an allergen is introduced. When those chemicals start to wane, the body craves another dose of the allergen to increase the levels of those chemicals again. These foods are usually eaten within a 3 day cycle, or less depending on the level of addiction. Some may be eaten daily, or every meal/snack/drink.
Why do I crave foods to which I'm sensitive?
Allergy Addiction Cycle
Addiction Pyramid
With corn, these cravings can manifest as a craving for any number (or multiple) of foods as corn is everywhere and it can be very hard to detect. One days craving may lead to ice cream, another day to Spaghetti-O's, baked beans, cookies, crackers, canned fruits, juices, salami, hotdogs, candy, chocolate, beer, etc.
My (Von) allergy to corn was based in a food allergy addiction cycle. It wasn't until I removed 80% of the corn from my diet (corn starch, corn syrup, etc) that I realized that corn was getting me high. My body was addicted, even though it was also making me sick. I would crave anything and everything in my cupboards. I actually started figuring out certain corn derivatives because I would crave the foods they were in - when you're starving for canned beets (corn vinegar), and will eat them straight out of the can (can't get them fast enough), you start wondering if maybe you might have a problem. After avoiding corn for two years, my body is finally starting to reprogram its addiction and is starting to react to corn as an aversion to it. It’s much easier to stop your body from eating something it doesn't like, rather than something it insanely wants. I have other food allergies as well, but none are instigators of the addiction cycle, only corn.
More resources:
WebMD - Allergy or Intolerance
Food Reactions.Org - Food Allergy & Intolerance
SAGA - Intolerance and Allergies
Women to Women: Allergy Symptoms
Allergy, Intolerance, & Sensitivity explained
Why do I crave foods to which I'm sensitive?
Allergy Addiction Cycle
Addiction Pyramid
Confused? Well so are we.
Actually I think the entire world is confused. The more I read up on this subject in order to shed some light on this confusing debate, the more confused I became. So don't worry, you're not alone in the head scratching.
It seems that when it comes to food intolerance, no one can agree on specifics. About the only agreement is this:
For it to be a food allergy, the immune system (IgE) is involved. Food intolerance the immune system isn't involved.
However that's about where the agreement separates. Some sites will tell you that if your food allergy doesn't show up on tests, then it has to be a food intolerance. We tend to disagree.
How reliable are Corn Allergy tests?
According to a study from March 2004, posted on Allergy Advisor.com "Traditionally, skin-specific and serum-specific IgE tests to maize are used to diagnose maize allergy. It is generally assumed that a negative result indicates the absence of maize allergy. However, it was recently shown that a negative skin-specific IgE and serum-specific IgE to maize flour had no clinical significance for most of the patients studied, and that food allergy to maize has to be proved by double-blind placebo-controlled food challenge studies"
The same study also states: "Many allergens have been isolated from maize, but the majority of them have not been clinically evaluated for their allergenic potential."
Even the Corn Refiner's Association admits: "Though allergens in other food systems have been well characterized, very little work has been devoted to identifying allergens in corn or corn ingredients."
So for starters, the tests are not accurate measures of IgE responses to corn, probably because the allergens in corn have not been fully identified to even make an accurate test for corn. Clearly for diagnosing a corn allergy, testing alone is not going to be an accurate measure of an IgE mediated food allergy reaction. (Despite what your allergist may tell you)
How can you tell if its a Corn Allergy or a Corn Intolerance? What is the difference?
One difference between a food allergy and a food intolerance is portions. A person with a food allergy usually cannot tolerate any amount of that allergen; however a person with a food intolerance can usually tolerate a small portion of an offending food but a larger portion will cause problems. Tolerances on this will differ from person to person whether they have a food allergy or intolerance.
The main difference however is the involvement of the immune system. Despite some sites claims to the contrary, there are a few symptoms which signify the immune system is getting involved. If you have any of the following, you most likely have a food allergy and should see your doctor immediately (you will want to get a script so you can have an Epipen handy).
These are:
Hives, urticaria, skin rash, eczema, - Skin may become red or flushed, raised bumps, itching, or fluid filled blisters.
Itching/burning around the mouth (or other contact area) usually accompanied with swelling.
Labored breathing, tightness of the chest, wheezing, asthma, shortness of breath.
Life-Threatening anaphylaxis.
Skin Contact reactions.
This is not an all inclusive list of food allergy reactions but these generally are not present with food intolerances and only present when the immune system is getting involved. (however there are always exceptions)
I should probably clarify here that when I say "immune system is involved" or maybe I should state that when 99% of the medical field states the "immune system is involved" they are referring only to the IgE immune response.
The immune system has many little warriors out there battling diseases and bacteria on our behalf. Some are IgA, IgG, IgM, IgD, and of course IgE. However, IgE is about the only one that has been even close to thoroughly researched and is the only immune response considered when declaring a food allergy.
IgG has also been proven to have reactions to foods; however these reactions are considered minor and temporary. Thus in medical circles, IgG mediated food allergies are considered intolerances despite the immune systems involvement. It is believed that if you avoid an IgG allergen long enough that the body will stop reacting to it. This is not true of an IgE allergy.
Genova Diagnostics explains the differences between IgE and IgG pretty simply:
IgE Mediated Allergies
Immediate onset (within minutes)
Circulating half life of 1-2 days
Permanent allergies
Stimulates histamine release
Includes foods, inhalants & molds
IgG Mediated Allergies
Delayed onset (4-72 hours)
Circulating half life of 21 days
Temporary allergies
Stimulates histamine release
Includes foods, herbs & spices
This is generally considered the differences between IgE and IgG allergies. Yet, an article by the University of South Carolina School of Medicine gives more time for IgE mediated responses:
"Type I hypersensitivity is also known as immediate or anaphylactic hypersensitivity. The reaction may involve skin (urticaria and eczema), eyes (conjunctivitis), nasopharynx (rhinorrhea, rhinitis), bronchopulmonary tissues (asthma) and gastrointestinal tract (gastroenteritis). The reaction may cause a range of symptoms from minor inconvenience to death. The reaction usually takes 15 - 30 minutes from the time of exposure to the antigen, although sometimes it may have a delayed onset (10 - 12 hours). Immediate hypersensitivity is mediated by IgE." - U of South Carolina, School of Medicine
So if your reactions to foods are more than minutes but less than hours, your chances are pretty good that its IgE mediated and would be considered an actual food allergy. Keep in mind, that though IgG mediated food allergies involve the immune system, the medical community still considers them “intolerances”.
What is a Food Intolerance (Corn Intolerance)?
Food Reactions.org and WebMD both give pretty clear cut and accurate definitions of real food intolerance.
Food Reactions.org states: "Food Intolerance is the inability to completely break down food into absorbable components due to lack or insufficient amounts of digestive enzymes. The unabsorbed food which remain in the digestive system causes the classic symptoms of bloating and cramps and others."
and
WebMD states: "Food intolerance is a digestive system response rather than an immune system response. It occurs when something in a food irritates a person's digestive system or when a person is unable to properly digest or breakdown, the food. Intolerance to lactose, which is found in milk and other dairy products, is the most common food intolerance."
Rules about food intolerance seem to be breaking down in recent years. These two definitions are more conservative than what some sites will tell you, as the discovery of IgG mediated food allergies (intolerances) has made some alter their definitions of food intolerance which I believe is misleading. (one such definition can be found at Australian Disability Online which lists asthma and other histamine type responses as a symptom of food intolerance.)
Food Intolerance symptoms should be mostly harmless, though when you're suffering through it you might wish it wasn't as these can be quite painful and debilitating. These symptoms include: (be aware these can also be present if it’s a food allergy)
Nausea
Bloating
Abdominal Pain
Diarrhea
These symptoms may start about a half hour after eating or drinking the problematic food, but they may also be delayed.
Rules of Thumb on differences between Corn Allergy and Corn Intolerance:
1. Immediate (minutes - Corn Allergy) vs. delayed reactions (hours - Corn Intolerance).
2. Immune system involvement: Hives (skin irritation), stuffy nose, chest congestion, swelling, anaphylaxis. (Food intolerance is mainly digestion issues.)
3. Skin contact problems - skin contact reactions have nothing to do with digestion and are only mediated by the immune system (except harmful chemicals which harm anyone’s skin). If you break out (eczema and acne included), have difficulty breathing, swelling, nausea, etc. by skin contact with a food item, you are most likely allergic to it (or something in it).
Important to note: The body can mask allergy symptoms as a way of survival. So some of these symptoms may not be noticeably present at first, or may not seem to be linked to a particular food. Masked allergies to foods are often present in persons with other skin (eczema and acne) conditions, airborne allergies, mood & behavioral issues, dark under eyes, sleep problems, and other miscellaneous conditions. (See Women to Women: Food Allergy Symptoms for more clues as to conditions which may be caused by hidden food allergies)
Telling the difference between an allergy and intolerance isn't always easy, but your family history will help. According to statistics on Australian Disability Online "Children who have one family member with asthma or eczema have a 20-40 per cent higher risk of developing allergy; if there are two or more family members with allergies then the risk increases to 50-80 per cent." Since asthma and eczema are often symptoms of allergic reactions themselves, its possible that the genetic allergy risk may be even higher than stated.
A full list of food allergy symptoms would be very long and there will be a separate article hopefully fully encompassing any and all symptoms you may experience. However in the meantime, Women to Women has an article which gives the most comprehensive list of systems. Keep in mind, that a food allergy can have all the same symptoms of a food intolerance (digestion issues), but a food intolerance will not have the symptoms of a food allergy (aka immune system response symptoms as explained earlier).
Where to start looking for Food Allergies?
If you just read through the last several paragraphs and you think you might have a food allergy but you don't know where to start, here are a few clues.
There are often two ways people react to allergy foods. They either love them (food allergy addiction) or they hate them. If there is a food you dislike (or strongly disliked as a small child), its possible that a food allergy may be the culprit. Keep in mind that this is not always accurate as the older you get the more memories you have about food, and you may stop liking foods based on non-food related memories. Aka you don't like orange jello because you associate it with the time you had that violent flu.
For parents of young children: Despite what some doctors and parenting advisors might say, young children (babies included) often refuse a food that they know is bad for them or has previously caused them problems. This can also include breast milk if the mother is eating a food to which the child is allergic. Children as they grow older may get finicky and like or dislike foods for other reasons, but pay attention to foods your child is refusing. Keep a list, including brand names as some brands may have added ingredients that others do not. This will help you narrow down possible food allergies. FYI: Enriched products (milks, flours) often have added corn and soy as carriers for the added vitamins.
According to FAAN, common food allergens are: Milk, Eggs, Peanut/Soy, Wheat (other related grains), Tree Nuts, Fish, Shellfish. The FDA only recognizes these 8 allergens to be serious enough to require labeling. FAAN does not recognize corn (nor does most of the USA) and you'll find many doctors will actually discourage a corn allergy even if the test results are positive. Corn Allergy and Intolerance is on the rise. If you do test positive to corn at all (in any even slight amount) you should investigate it through diet. Avoidance and retrial, is the only accurate way to know if it’s going to be a real issue.
Food Allergy Addiction is also something for which to watch out. It sounds funny or like a "fat persons" disease, but it isn't necessarily. Physiologically, the body becomes dependant (addicted) to the allergens presence and starts a craving for it. There are several theories for this (see below links) which center more on the chemical reaction that happens in the body when an allergen is introduced. When those chemicals start to wane, the body craves another dose of the allergen to increase the levels of those chemicals again. These foods are usually eaten within a 3 day cycle, or less depending on the level of addiction. Some may be eaten daily, or every meal/snack/drink.
Why do I crave foods to which I'm sensitive?
Allergy Addiction Cycle
Addiction Pyramid
With corn, these cravings can manifest as a craving for any number (or multiple) of foods as corn is everywhere and it can be very hard to detect. One days craving may lead to ice cream, another day to Spaghetti-O's, baked beans, cookies, crackers, canned fruits, juices, salami, hotdogs, candy, chocolate, beer, etc.
My (Von) allergy to corn was based in a food allergy addiction cycle. It wasn't until I removed 80% of the corn from my diet (corn starch, corn syrup, etc) that I realized that corn was getting me high. My body was addicted, even though it was also making me sick. I would crave anything and everything in my cupboards. I actually started figuring out certain corn derivatives because I would crave the foods they were in - when you're starving for canned beets (corn vinegar), and will eat them straight out of the can (can't get them fast enough), you start wondering if maybe you might have a problem. After avoiding corn for two years, my body is finally starting to reprogram its addiction and is starting to react to corn as an aversion to it. It’s much easier to stop your body from eating something it doesn't like, rather than something it insanely wants. I have other food allergies as well, but none are instigators of the addiction cycle, only corn.
More resources:
WebMD - Allergy or Intolerance
Food Reactions.Org - Food Allergy & Intolerance
SAGA - Intolerance and Allergies
Women to Women: Allergy Symptoms
Allergy, Intolerance, & Sensitivity explained
Why do I crave foods to which I'm sensitive?
Allergy Addiction Cycle
Addiction Pyramid
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