Food allergies are sometimes confused with food intolerances. The main difference: In a food allergy, the immune system fights parts of the food as foreign bodies. More about it as well as symptoms, causes, and therapy of a food allergy. Around 1 to 2 percent of the population suffers from a real food allergy. In these cases, the immune system is allergic to certain foods. An allergy is a bad reaction of the immune system to actually harmless, foreign substances.
A reaction does not appear until the second contact with the triggering substance (allergen) at the earliest. The first time the so-called sensitization takes place, i.e. the immune system forms antibodies against the apparently hostile substance, which it is supposed to fight off. If the body comes into contact with the allergen again, large amounts of these antibodies are reproduced. They fight the substance and an allergic reaction occurs. Defense cells release various highly effective biochemical substances such as histamine, which are then responsible for the classic symptoms.
Common food allergy triggers are:
- Different types of fruit and vegetables
Most adults have pollen-associated food allergies in hay fever (cross allergy). The structure of the allergenic molecules in pollen are similar to some structures in some foods. The immune system, so to speak, confuses the molecule and then reacts with an allergy to different foods.
The symptoms of the allergy range from skin rashes with itching and wheals to gastrointestinal disorders to shortness of breath or, in the worst case, circulatory failure. The most common cross allergies:
- Birch, alder, hazelnut – nuts, apples, other stone and pome fruits, potatoes
- Grasses – tomato, peanut, legumes,
- Mugwort – celery, spices, carrots
A food allergy must be differentiated from food intolerance. There is no immune reaction here. It is triggered, for example, by foods that contain a lot of histamines. In other forms, there is a lack of enzymes that are supposed to break down certain substances in the body (e.g. lactose intolerance). In addition, some dyes or preservatives in the body can cause a direct release of histamine. The symptoms are mostly similar to those of a real food allergy.
Identifying the triggering allergen can be very difficult, especially due to today’s variety of convenience foods. The simplest test is the so-called prick test. Various test solutions are stabbed into the skin. If there is an allergy, a wheal will form at this point after approx. 20 minutes. In the case of food, it may be necessary not only to use the test solution but to place the food itself on the skin or to scratch a little and then prick the skin in order to obtain a reliable result. If the allergen cannot yet be found, there is the option of a provocation test. This means that the suspicious food is eaten in low doses under medical supervision in order to provoke an allergic reaction. A blood test, in which the antibodies against a suspected allergen can be detected, can also be helpful.
If the allergic reaction is not too strong, drugs that block the histamine in the body (antihistamines) are usually sufficient for therapy. In more severe cases, cortisone is used to suppress the immune response. For patients who have ever had a massive allergic reaction, it is advisable to always have an emergency kit with them, consisting of an antihistamine, cortisone, and an adrenaline supplement, in case a circulatory reaction occurs.
The best therapy, of course, is to avoid the offending food. However, some allergens change depending on the preparation, so that, for example, many patients with an apple allergy cannot tolerate the raw apple, but have no problems with the apple in cooked or baked form. Finished products on which the ingredients are not adequately declared can also cause difficulties. It is advisable not to use it.