Pseudoallergy (synonyms: Abnormal drug effect; Drug-induced development of tolerance; Drug reaction n.d.; Drug intolerance; Drug hypersensitivity; Histamine intolerance (HIT)/histaminosis; Histamine intolerance; Histamine hypersensitivity; Idiosyncrasia; ICD-10 T78.1: Other food intolerance, not elsewhere classified) is to be classified in the group of “nonallergic or nonimmunologic hypersensitivities” because no immunologic mechanisms are detectable. The symptoms resemble an allergy of the immediate type.
The group of pseudoallergies includes pharmacological intolerances (drugs), intolerances to food additives such as dyes or preservatives, and biogenic amines.
The prevalence (disease frequency) for pseudoallergy to foods and additives is approximately 1%.
Course and prognosis: For the prognosis of pseudoallergy, the identification of the trigger is crucial. Provocation tests and omission diets are used to determine this. Once the trigger(s) of the pseudoallergy have been diagnosed, they must be avoided (restrictive diet), as this is the only way for the affected person to achieve freedom from symptoms. To ensure that the diet remains balanced despite restrictions, training by a nutritionist with allergy expertise is recommended. Often a pseudoallergy heals spontaneously. Therefore, the diagnosis should be checked at regular intervals so that the patient does not restrict his diet without reason.