Food allergens

As with other natural allergens, they are usually mixtures in which numerous substances with different immunogenicity are present. Only a part of them can be considered as allergens (see below food allergy). From a practical allergological point of view, food allergens can be divided into plant and animal allergens.

With a normal diet, about 120 different allergies of potent foods are absorbed in 24 hours (Jaeger L. 2001). The allergy spectrum depends on the regional eating habits (see below).

Classification of food allergens (NMA) according to physico-chemical properties:

• Class 1 NMA = stable (heat and acid stable NMA): cow's milk (see below cow's milk allergy), hen's egg, fish proteins, meat proteins (see also bird-egg syndrome), peanut. Sensitization route: gastrointestinal.
• Class 2 NMA = labile (mostly heat-labile or chemo-labile NMA): birch, apple, spice allergies. Sensitization route: oral or inhalation.

Classification of food allergens (NMA) according to protein families (Bet-v-1- homologues = main allergen of birch [silver birch; white birch]. All similar proteins are the basis of cross-reactions and are summarized as Bet-v-1 homologues:

• Profilins: ubiquitous proteins which are important for the formation of the cytoskeleton of the cell. These have important functions both for the movement within the cell and for the transmission of signals between cells. They are found in pollen as well as in food, are rarely allergenic, but are responsible for many cross-reactions.
• Oleosins: Fat-soluble allergens that do not occur in aqueous extracts.
• Seed Storage Proteins: Stable proteins that make up a large part of the proteins in nuts, seeds, legumes and cereals.
• Lipid Transfer Proteins (LTP): heat and acid stable proteins responsible for severe gastrointestinal reactions after fruit and vegetable consumption. Especially in Mediterranean countries. Sensitization is achieved, for example, by eating ripe peaches. The peach allergen Pru p 3 has a great structural similarity to other representatives of this allergen family.

Separation of the allergen mixtures is carried out by physicochemical methods (immunoblot). Allergen characterisation is carried out by chemical or genetic engineering methods.

Nomenclature (WHO/IUIS): The name of such an allergen consists of the first 3 letters of the genus (e.g. bovine - Bos domesticus Bos, the letters of the species (Bos domesticus Bos d), a numbering with Arabic numerals in the order of characterisation (Bos domesticus d 1 - d8). On the basis of the previously known bovine allergens and their biological properties, the following exemplary profile results.

• Bos d 2 Lipocalin
• Bos d 3 S100 calcium-binding protein A7
• Bos d 4 alpha-lactalbumin
• Bos d 5 Beta-lactoglobulin
• Bos d 6 Serum albumin
• Bos d 7 Immunoglobulin
• Bos d 8 Caseins
• Bos d 9 alphaS1-casein
• Bos d 10 alphaS2-casein
• Bos d 11 beta-casein
• Bos d 12 kappa-casein

Potentially anaphylactic reactions are mainly detected in cases of sensitization by (in decreasing frequency (Official Journal of the Eur. Union of 28.11.2007):

• Cereals containing gluten (wheat, rye, barley, oats, spelt, kamut)
• Crustaceans
• Pome and stone fruit ( apple)
• eggs or egg products (see below egg protein allergy)
• Fish and fish products
• Peanut
• Soya and soya products
• Milk and milk products
• Nuts (hazelnuts, cashew nuts, macadamia nuts, almonds, Brazil nuts, pistachios, walnuts and their products)
• Celery and products
• Mustard and mustard products
• Sesame and sesame products
• Lupine and lupine products
• Molluscs.

Examples of diseases that can be triggered or aggravated by class 1 food allergens: The stable food allergens are primarily responsible for systemic reactions:

• Angioedema
• acute urticaria
• Worsening of atopic eczema.

Examples of diseases caused by class 2 food allergens:

• Birch pollen-nut-nut pome syndrome
• Oral allergy syndrome
• Celery-carrot-mugwort spice syndrome
• Latex fruit syndrome.

1. Bauer X, Gahnz G (2002) Pumpkin seed allergy in the form of food intolerance and occupational contact urticaria. Dermol Occupation Environ Environ Dermatol 50: 178-179
2. Hausen BM, Vieluf K (1997) Allergy plants, plant allergens. Ecomed Publishing House Landsberg/Munich 540-542

3. Jaeger L (2002) Food allergens. In: L. Jaeger B Wüthrich (Hrsg) Food allergies and intolerances. Urban&Fischer Munich Jena 2002

4. Jäger L, Wüthrich B (1998) Food allergies and intolerances. Gustav Fischer, Ulm Stuttgart Jena Lübeck p. 85

5. Kleine-Tebbe J et al (2010) Allergen families and molecular diagnostics of IgE-mediated food galleries: from theory to practice. Allergo J 19: 251-263
6. Kleine-Tebbe J, Herold DA (2003) Cross-reactive allergen clusters in pollen associated food allergy. dermatologist 54: 130-137
7. Schäfer T (2008) Epidemiology of food allergy in Europe. Allergology 31: 255-263

8. Wüthrich B et al (1995) Allergy to cheese produced from sheep's and goat's milk but not from cheese from cow's milk. J Allergy Clin Immunol 96: 270-273

9. Zuberbier T (2008) Food Allergies - Epidemiology in Berlin. Allergology 31: 264-273

Characteristics of relevant allergens (pollen and food allergens; modified by Wüthrich and Hausen/Vieluf)