Pseudoallergies
In a narrow sense, the term "pseudoallergy" refers to all immediate-type reactions caused by immune system malfunctions (mast cells, basophils) that are not mediated by specific IgE antibodies (sIgE). In a broader sense, intolerances based on metabolic disorders (e.g. enzyme defects), such as histamine intolerance, are often also included under pseudoallergic reactions, as they can produce allergy-like symptoms. Pseudoallergies typically occur within minutes to a few hours. Immediate-type symptoms in pseudoallergies are generally dose-dependent, which means that small amounts of the substance may be tolerated. A reaction is usually only triggered once an individual – and often highly variable – threshold is exceeded.
Triggers of Pseudoallergies
Suspected triggers of pseudoallergies in foods include artificial additives such as preservatives, which prevent spoilage, as well as colourants, emulsifiers, and flavour enhancers, which improve the appearance, texture, and taste of foods.
Natural ingredients in foods, such as salicylates or benzoates (e.g. E211), are also considered possible triggers of pseudoallergic reactions. High levels of salicylates (salts of salicylic acid) are found in berries, fruits (e.g. oranges, pineapples, grapes), olives, spices (curry, turmeric, cinnamon, mustard), herbs (peppermint, basil), and wine. Benzoates (salts of benzoic acid), which are also used as preservatives, naturally occur in berries (e.g. blueberries, raspberries), fruits (e.g. plums), honey, tea, cocoa, and fermented dairy products.
Diagnosing a Pseudoallergy
Traditional laboratory tests for immediate-type allergic reactions, such as IgE detection in the blood, do not produce meaningful results in cases of pseudoallergy. Individual detection of pseudoallergic reactions is performed in vitro by means of the Basophil Activation Test (BAT). Based on positive BAT results, a diagnosis of pseudoallergy can subsequently be confirmed on an outpatient basis through adherence to a suitable elimination diet (low-pseudoallergen diet), which may be followed by oral provocation testing if necessary.
