As an allergist, I am frequently asked to help patients determine: 1) if they have had an allergic reaction; 2) what was or is the cause?; and 3) what is the optimal way to treat this problem?
1) An allergy evaluation includes carefully questioning and then examining the patient, followed by diagnostic allergy skin tests and sometimes selected blood tests. Classic allergic reactions include: hives, swelling of the eyelids or tongue or throat, red and itchy eyes, runny and congested nose, trouble breathing in the chest, and lightheadedness or dizziness.
2) If I suspect the patient had an allergic reaction, then I try to confirm the suspected cause or screen the patient's environment using selected allergy skin tests. Whole foods can be easily tested for by skin tests if the test is available. This is a big problem. Many foods do not have an Food and Drug Administration approved skin test or lab test.
Two other groups can cause adverse reactions to foods. First are vasoactive amines. These are naturally occurring chemicals in foods, which can cause reactions in people. Three examples are caffeine, salicylates, and tyramine. Second, the large category of additives are possible causes. What are additives? Anything added to our food and drink.
My list of additives includes (with examples in parenthesis):
excipients (an umbrella term for supposedly inactive substances that aid in preparation of the active substance, for example the coating of a capsule or the fibers used to hold powdery chemicals together in pills),
outside chemicals (insecticides and/or vitamins C is commonly sprayed on meat and produce),
contaminants from preparation of food (restaurants use the same utensils and grill for most customers).
Regrettably, there is no available skin test for these substances. Why? Because the Food and Drug Administration would not approve tests that were submitted. Manufacturers grew weary of waiting - time IS money and this is business - so they gave up. The only way is to directly challenge the patient with the suspected substance and then observe the results. The advantage of this approach is confirmation of the cause. The disadvantage is that the patients may experience a reactivation of their symptoms. If the reaction is severe, one should be prepared for the risk, or not go down this road. I usually do not recommend this step.
3) If you suspect a food is causing your reactions, watch what you eat very, very carefully. Keep a written diary. Read your list of ingredients. Our foods in the U.S.A. are loaded with additives. This has helped to give rise to organic foods. What's my position? I personally think an all organic diet would significantly reduce the number of adverse reactions, including allergic, to foods and we would have less obesity in the U.S.A. Go for it. I am not endorsing one brand over another. I try to, although my family thinks the food tastes blander. It is, because there are no additives.
Here's my true life anecdote. When I was a fellow-in-training, I saw a man with hives. Eventually I determined that his toothpaste was the cause. Back then, the manufacturers were more flexible. The manufacturer provided us with the individual ingredients. We did oral challenges with each ingredient. An excipient turn out to be the cause. After he eliminated that brand of toothpaste and avoided all other personal care products with that excipient listed, he became free of hives that had plagued him for years.