Food allergy (synonyms: IgE-mediated food allergy; food allergy; NMA; food allergy-immunologic reaction; food intolerance; food hypersensitivity; ICD-10-GM T78.1: Other food intolerance, not elsewhere classified) is a hypersensitivity reaction caused by immunologic mechanisms after food intake. Food allergy is usually an IgE-mediated allergic reaction (type 1 allergy); it may be antibody- or cell-mediated.
Two forms of food allergy are distinguished with respect to their triggers:
- Primary food allergy: due to gastrointestinal sensitization to predominantly stable food allergens (e.g., milk and chicken egg whites, soy, wheat, peanut, and tree nuts).
- Secondary food allergy: sensitization to aeroallergens, e.g., pollen, and resulting cross-allergy to food allergens that are often unstable (90% of cases; occur more frequently in adults than in children)
Sex ratio: males to females is 1: 2. Possible causes include genetic influences, increased exposure (e.g., cooking), and hormonal factors.
Frequency peak: The maximum occurrence of food allergies is in infancy.
The prevalence (disease incidence) is 4-8% (in Germany). The highest prevalence of primary sensitization to food is in infancy at about 6.6% and decreases to about 3.2% in the 5th year of life. The frequency of occurrence of food allergies is also determined by the consumption habits of individual countries. For example, peanut allergies occur more frequently in the USA and Great Britain than in Germany. Fish allergies are more common in Spain and Portugal and wheat allergies in Germany.
Course and prognosis: All foods can trigger an allergic reaction (primary food allergy). The most common triggers include nuts, milk, eggs, spices, fish and shellfish. Children are particularly allergic to cow’s milk, soy and chicken eggs, while adolescents and adults are allergic to raw vegetables and fruits, spices and nuts. Once the allergy-causing food has been diagnosed (see laboratory diagnostics below), the affected person should avoid eating it if possible (restricted diet) in order to remain symptom-free. To ensure that the diet remains balanced despite restrictions, training by a nutritionist with allergy expertise is recommended. In rare cases, anaphylactic shock, which leads to a circulatory collapse, can occur in the context of a food allergy. Note: Fish allergy sufferers do not all have to completely avoid fish. Some tolerate certain types of fish and therefore do not need to give up this protein source despite their hypersensitivity.A food allergy can turn into tolerance: If the food allergy occurred in infancy, it usually regresses by the age of six. The prognosis of spontaneous remission (complete or partial disappearance of a disease) is particularly favorable for cow’s milk protein, chicken egg protein, wheat and soy allergies. Food allergies in adulthood usually persist throughout life.
Comorbidities (concomitant diseases): two-thirds of patients have atopic diseases such as allergic rhinitis, bronchial asthma, and atopic dermatitis.
