Thursday, March 01, 2007

Corn a prevalent cause of atopic dermatitis

Atopic dermatitis is a skin rash (such as eczema) or other skin condition caused by an allergic reaction. In a Lithuanian study of 108 children with atopic dermatitis, researchers tested the children via skin prick test for the most common allergens, and via skin patch test for 25 foods.

Only the "most common allergens"--milk, eggs, wheat, rice, cod, pork, chicken, carrot (I guess these must be the top 8 in Lithuania) were tested via skin prick tests. The total blood IgE was also measured. 73.1% of the test subjects had normal levels of overall blood IgE, not elevated at all. They did not test IgE levels to individual allergens.

4.63% had a positive skin prick test, and 68.5% of the children showed positive results on the skin patch test. In total, only one-fifth of the subjects studied were not found to have food allergy. The vast majority were shown to have AD caused by food reactions.

Out of the 25 foods patch-tested, the most common causes of atopic dermatitis were soy, milk, peanuts, carrot, egg whites, wheat and corn, in that order. In this Lithuanian study, as seems to be the general case worldwide, the most common causes for food-related delayed AD were soy (35.2%), milk (25%) and peanuts (19.4%). 14.8% of the delayed reactions were caused by corn, as compared to carrot (18.5%), wheat and egg white (both 17.6%) and rye (11.1%).

Of the children with atopic dermatitis in the study, over half had mild AD and 17% had severe AD.

Here's the interesting thing: In the group of children with severe delayed-type reactions, corn was the most common cause. 37.5% of the most severe cases of AD were caused by corn, beating out more commonly-suspected allergens such as peanut (23.8%), soy (10.5%), whey (33.3%), and egg white (18.2%.

I wish they would have done skin-prick testing for all 25 of the foods they patch tested. For the tests they did do, the skin patch test was, as expected (and as showed in many other studies--see citations), much more reliable than skin prick testing in correctly diagnosing atopic dermatitis caused by food allergies. As mentioned by the authors, other studies also show a much higher accuracy in diagnosing delayed food-related AD with patch testing.

A Finnish study showed that 16 out of 34 children with severe atopic dermatitis had positive skin-prick tests to corn.

A number of other studies have also shown corn to be among the most prevalent causes of atopic dermatitis. In most of these cases, a skin-prick test will give a negative result even though the atopic dermatitis is caused by a food reaction.

Eosiniphilic esophagitis is another condition for which corn is one of the most common triggers. According to this study, EOS-related food reactions caused by egg, milk and soy were more likely to be diagnosed by skin-prick testing, while issues caused by corn, soy or wheat were more likely to be found by patch testing.

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