Most important for health care consumers to know is that the immune system is very complex, and that there are a number of ways that your body can react to foods, so there a number of ways to test. Some tests are very accurate and reliable, but others are less so, and are more open to interpretation.
The classic allergic reaction, which includes hives, difficulty breathing, and anaphylaxis, is caused by a rapid release of histamine. These allergic reactions happen very quickly, and are of the same type as hay fever or bee allergies. The most common foods causing this type of allergic reaction are peanuts, tree nuts, milk, eggs, soy and wheat. These types of allergies have clear, dramatic symptoms, and can be tested via blood tests. The results are usually definitive and reliable.
Less clear and less well-understood are what are technically termed food intolerances. The symptoms of these include headaches, joint pains, eczema, IBS, malaise and other symptoms. When dealing with these types of food reactions, lab tests are rarely as definitive. Occasionally, one or two foods will come up high on a fairly extensive list. Other times, a group of foods will come up high that can be clearly identified by a food type, e.g. legumes, nuts, wheat, or citrus fruits. In these cases, avoidance of the foods or food groups is appropriate, provided that avoidance results in symptom relief.
In a third, common situation, a large number of foods will come up as reactive without a clear pattern. In these situations, there are additional factors at play, including increased gut permeability (“leaky gut”) or increased immune activity due to other causes. Technology for diagnosing and understanding these types of food reactions is still developing, and the jury is very much out. When dealing with unclear testing results, I tend to encourage a regime of overall healthy eating, emphasizing whole foods. I usually avoid restrictive diets, as I have seen that the stress of avoidance and a restricted diet can be equally as challenging as the symptoms the patient is experiencing. I also often seek other medical causes or pursue other methods of treatment beyond food avoidance, such as constitutional homeopathy, supplements or herbal medicine.