Soy allergy T78.1

Allergens detected in soya:

• Gly m1: protamine; inhalation allergy; occupational in contact with soya dust during transport or production.
• Gly m2 ( Defensin): coat protein, of soya products.
• Gly m3 ( profilin): pollen-associated food allergy, especially in adolescents and adults; Bet-v-1 homologue.
• Gly m4 (PR 10 protein): in the presence of birch pollen allergy; Bet-v-1 homologue Gly m4, which is responsible for soybean allergies in adults, is a major allergen that shows considerable structural similarity to the birch pollen major allergen Bet-v-1. The PR-10 protein (PR = pathogenesis-related or plant defence related) is a so-called "plant stress protein". Plant stress proteins are substances that the plant produces as a defence reaction after infections. The majority of birch pollen allergy sufferers show a cross-reaction against the soy protein from the family of thermo- and acid-labile Bet-v-1 homologous cross-reactions due to allergens homologous to Bet-v-1 are found in food intake of soy, apple, pear, cherry, apricot, carrot, hazelnut, parsley, asparagus and celery and in pollen inhalation of hazelnut, alder and hornbeam. It is likely that at least 10% of birch allergy sufferers develop clinical symptoms after eating unprocessed or low-grade processed soya products. The allergen content increases with the development of soya seedlings and during storage. The allergenicity decreases with fermentation and heating. Due to low concentrations of Gly m4 in commercial soy extracts, the soy RAST/CAP is often negative.
• Gly m5: beta-conglycinin; minor allergen; gastrointestinal sensitization, thus classical food allergy; especially infants and toddlers are affected. Gly m5 is believed to be responsible, among other things, for the triggering of an "exertion-induced" food allergy after soya consumption. In the case of Gly m5, the gastrointestinal breakdown process varies greatly from one individual to another. Both Gly m5 and Gly m6 can trigger severe allergic reactions.
• Gly m6 (glycinin): rare; mainly adults are affected. Gly m6 (glycinin) is a major allergen which is thermostable up to 95 °C; it is relatively resistant to proteolysis. Cross-reactions are possible with earth nut or lupine.
• Gly m 6 Glycinin (legume)
• Gly m 7 Seed biotinylated protein
• Gly m 8 2S albumin
• more than 10 other Gly m proteins whose allergenicity has not yet been further defined.
• Trypsin inhibitors: Soya contains several enzyme inhibitors which have a protective function against proteases, e.g. of fungi. From an allergological point of view, the 20 kDa trypsin inhibitor is particularly important. It is also found in soya lecithin and can trigger anaphylactic reactions.

1. The "classic", rare (infancy; about 15% of soya allergy sufferers) primary food allergy. In this case, gastrointestinally absorbed stable soya proteins are the decisive allergens.
2. The more frequent (adolescence and adulthood) pollen-associated (secondary) food allergy, which develops after inhalation sensitisation by birch pollen allergens.
3. The inhalation allergy caused by inhalation of large amounts of soya shell proteins (observed in port workers during industrial cargo unloading of soya).

• Soy allergy has been found in 6% of cases in children with atopy. The most common form of soybean allergy is (in Central Europe) triggered by a birch pollen-associated cross-reaction. It is expected that every 10th birch pollen allergy sufferer cross-reacts with soya. Non-pollen-associated cross-reactions can occur with other food allergies from the legume family (beans, peas, peanuts, lentils). Soya products can be present in many foods. Soy is often used as a primary source of protein, as an emulsifier or as an oil in salad oils, baking fats or margarines. Soybeans are also used to produce soy lecithin. Lecithins are important natural surfactants (emulsifiers) for food and animal feed (generally approved in the EU as food additive E 322 for foods in general, including baby food). Soybean oil is a vegetable oil obtained from soybeans and is mainly used as a foodstuff. The main use of soybean oil is in food, where it is used for a wide range of applications from salad oils, cooking fats to margarine.
• A particular hazard is posed by unidentified soy protein, e.g. in coffee whiteners, diabetic pastries or meat substitutes (heat-stable). According to the Labelling Ordinance, it is sufficient to use the term "vegetable protein product" in a list of ingredients; no special reference needs to be made to soya. To what extent a specific immunotherapy ( SIT) can improve a birch pollen-associated soy allergy has not yet been sufficiently clarified.

1. Holzhauser et al (2009) Soybean (Glycine max) allergy in Europe: Gly m5 (beta-conglycinin) and Gly m6 (glycinin) are potential diagnostic markers for severe allergic reactions to soy. J Allergy Clin Immunol 123: 452-458
2. Krishnan et al (2009) All three subunits of soybean beta-conglycinin are potential food allergens. J Agric Food Chem 11: 938-943
3. Treudler R et al (2010) Increasing popularity of soy: how to advise birch pollen allergy sufferers correctly. Allergo J 19: 243-250