Classic Food Allergy (IgE-mediated)
Classic food allergy is a type I hypersensitivity reaction directed against food proteins and mediated by IgE antibodies. This type of allergic reaction is always preceded by a sensitization phase during which the affected individual does not yet experience any symptoms. The release of excessive amounts of allergen-specific IgE (sIgE) is a central event in the development of an allergy.
Symptoms of Classic Food Allergy
Typical symptoms of type I allergies include:
- Contraction of smooth muscle cells
- Mucus secretion
- Swelling
- Itching
- Redness
- Pain
- Life-threatening anaphylactic reaction
Which foods most commonly trigger allergies?
The most frequent triggers of primary food allergies include:
- Peanuts
- Tree nuts
- Soya
- Fish and shellfish
- Cow’s milk
- Wheat
- Hen’s egg
Classic Food Allergy – The Example of Wheat Allergy
Reactions triggered by wheat allergens can occur within minutes to a few hours after eating (immediate-type allergy). The range of symptoms extends from acute local symptoms in the gastrointestinal tract such as vomiting, nausea, diarrhoea, constipation and bloating, to skin reactions (e.g. urticaria, worsening of eczema in atopic dermatitis), and even to severe systemic responses such as anaphylactic shock, which can be fatal. Children most commonly develop an immediate-type wheat allergy (prevalence 9%), which usually resolves by school age and persists into adulthood in only a few patients (prevalence 0.4%).
Diagnostics
Measuring the concentration of IgE specific to a potential allergen in the serum can be done using single allergens, allergen mixtures or complete allergen panels. In classic IgE in vitro diagnostics, the reactivity of sIgE antibodies to whole allergen extracts is often assessed. All allergen sources, including foods, usually contain multiple allergy-relevant proteins.
To confirm the diagnosis of an IgE-mediated food allergy and to guide differentiated therapeutic recommendations, precise identification of the triggering allergens is essential. Sensitization to, for example, water-soluble components of wheat can best be detected by determining sIgE against a total protein extract of wheat.
A positive result in sIgE testing only indicates sensitization to the tested food and does not automatically confirm a clinical allergy. The suspected diagnosis should therefore be confirmed by a laboratory-based test procedure (e.g. Basophil Activation Test, BAT) or directly on the patient (oral provocation, skin prick test). Provocation testing, particularly in highly sensitized patients, should only be carried out under the supervision of a healthcare professional trained in allergy diagnostics to ensure appropriate emergency treatment in the event of severe anaphylactic reactions.
