An allergic reaction can generally be regarded as a hypersensitivity reaction of the immune system (the body's own defense), which is supposed to recognize and destroy harmful substances. In a food allergy, even the smallest concentrations of a food in a short time can lead to allergic body reactions.
Who is affected?
One in four in Germany believes that they suffer from a food allergy, but only about three to ten percent of children are allergic to food (80 percent of them lose their food allergy in their first few years) and only one to two percent adults (women twice as likely as men) are affected - that's an estimated five percent of Germans. After the allergies to pollens and dust mites, the food allergy with eczema is the third most common allergy phenomenon in Germany.
Causes of a food allergy
In addition to the genetic disposition, the lack of stimulation of the immune system is attributed to an ever more sterile environment for the increase in allergies in general. The increasing contamination of the environment is also discussed as a trigger. However, food allergies are also dependent on eating habits. Clinical experience shows that, for example, increased consumption of soy also increases the allergic reactions to it.
A significantly expanded range of foods (for example, exotic fruits such as kiwis and litchies), which is available all year round, and an increasing trend towards heavily processed foods are also associated with an increase in potential allergens. However, drastic increases in food allergies are still not recorded in Germany.
Frequently - especially in adults - also allergen communities occur, so-called cross-allergies. These can be communities between foods among themselves, but also often between foods and pollen (pollen-associated food allergy).
Often, atopic dermatitis in children is also associated with a food allergy. However, scientific studies have shown that neurodermatitis is not the result of a genuine food allergy. But cross-allergies with food are not uncommon in neurodermatitis, but these are difficult to distinguish from the actual neurodermatitis by the similar symptoms (itchy skin irritations).
How does a food allergy develop?
Food allergies are mostly due to an allergic reaction of the so-called immediate type. Here, the symptoms occur immediately after ingestion of the food. The first contact with the triggering substance, the allergen (= antigen) runs without external symptoms; but it comes in the body to form antibodies (Ig-E), which in a second contact the release of pro-inflammatory substances, the so-called mediators (eg histamine) cause, which cause the actual allergic reactions of the body. Often, these reactions are localized.
However, extending the allergic response to the entire organism can lead to a life-threatening condition, anaphylactic shock. This is associated with a sharp fall in blood pressure, an increase in heart rate, a narrowing of the bronchi and swelling and edema around the larynx.
In addition to food allergies, non-immunological food intolerances also occur. These are caused by enzyme defects (for example lactose intolerance due to the absence of the enzyme lactase). Certain body parts can not be digested by the body.
In contrast to food allergies, pseudoallergic reactions often occur as a function of the absorbed dose of a triggering substance in the food.
These can be found in a variety of food additives such as colors, flavorings and preservatives, aspirin and other natural salicylates (much in soft fruits, oranges, apricots, pineapples, cucumbers, olives, grapes, wine, especially in spices) and biogenic amines such as Histamine, tyramine or serotonin. These are either naturally contained in the food in high concentration (for example, red wine, fish) or occur during fermentation (sauerkraut) or Fermetation (cheese) or in the spoilage of food by microorganisms.
Often pseudoallergy symptoms such as hives, headache, nausea, diarrhea, and itching only appear after several hours of delay, but persist longer than with food allergy. All of the non-immunological reactions of the body to certain foods do not produce antibodies because the body reacts directly to these foods. The symptoms often resemble that of a true food allergy.
Symptoms of a food allergy
Food allergens trigger very different reactions:
- Skin: rash (eczema), hives (urticaria): redness and itchy wheals and sometimes swelling (edema)
- Eyes: edema, allergic conjunctivitis (allergic conjunctivitis)
- Nose: runny nose (allergic rhinitis), sneezing
- Quincke edema: Swelling of the body
- Mouth: Itchy, inflamed oral mucosa, swollen tongue and palate
- Bronchi / Lungs: cough, allergic asthma
- Gastrointestinal area: diarrhea, vomiting, pressure and fullness
- Circulation: anaphylactic shock (rare), drop in blood pressure, cardiac arrhythmia, palpitations, headache
Food allergies of infancy and childhood differ in principle from those of adults, as children react allergic especially to substances that enter the body through the digestive tract (intestinal allergens) and adults on substances that are inhaled (inhaled allergens). Even the allergens themselves are different in the different ages.
Which are the most common food allergies?
Especially common are:
- Cow's milk allergy
- Hen's egg allergy
- Allergies to fruits, nuts and vegetables
- spice allergies
- Allergy to fish and shellfish
- Pollen-associated food allergy
Food allergy: what should be considered?
The best therapy is to avoid the foods that trigger the allergy. However, this can sometimes be very difficult, as there are also hidden ingredients (nuts, soy, milk protein, etc.) that do not necessarily have to be declared. This leaves only the possibility to avoid processed foods as far as possible or to always buy the same branded products with which you have already had good experiences.
If a food allergy is suspected, the family doctor should first be asked to rule out other gastrointestinal diseases. If this is the case, always consult an experienced allergist who can narrow down his diagnosis of allergy to a particular food through various tests. A food diary can also lead to helpful hints for the allergist.
As a precaution, breastfeeding may be recommended in case of suspected inherited allergies in children, which should last at least six months.