Their website says:
This helps to prevent our goodies from crumbling, a job normally performed by gluten in mainstream foods. It is a necessity in gluten-free baking. Xanthan comes from the dried cell coat of a microorganism called Zanthomonas campestris. Though it sounds chemical, it is actually an all natural ingredient. Xanthan gum is derived from the fermentation of corn sugars, all corn sugars are removed in the processing of xanthan gum. Xanthan gum contains no corn protein and is considered to be corn-free. We have had no reports of problems with our products containing xanthan gum. We recognize the severity of food allergies and encourage you to make a choice based on your own comfort level with this ingredient.
If you have had a reaction to Enjoy Life products, or to any product containing xanthan gum grown on corn, please write to them and let them know.
Even if you have never tried Enjoy Life products, but you avoid xanthan gum, please write to them. You can tell the company that you avoid buying their products because you have had reactions to xanthan gum in the past. Knowing that they are losing customers over this should be helpful.
If enough people write to them letting them know that some corn-allergic people do indeed react to xanthan gum, perhaps they will change their product formulation or at least their labeling.
In my letter, I asked them to consider changing their labeling to clarify that the xanthan gum is grown on corn and the products containing that ingredient are not completely corn-free. As it is, I feel that labeling the products corn-free without any indication on the product that there is a corn-derived ingredient is misleading and dangerous.
I also told them that if they changed the recipes on any of their products to make them truly free of our allergens, we would buy them.