Onion allergyT78.1

Like garlic (but also asparagus, chives and leek),onions (Allium cepa; kitchen onion) belong to the Lilaceae, the leek family. Onions are prepared and eaten in different ways. Raw with oil and salt, roasted, fried, steamed. They are served with meat, fish and also in fast food like hamburgers, matjes, kebabs, pizza, steak etc.

Type I reactions: Food allergies to kitchen onions are rare. Immediate reactions are described as urticaria, bronchial asthma and/or anaphylactic reactions (Valdivieso R et al. 1994). This type of reaction is mainly caused by raw onions (thermolability of the allergen). Cooked onions are mostly tolerated.

Other clinical cases:

• Airborne urticaria with angioedema during the preparation of an onion dish. Exercise-induced anaphylaxis: Pérez-Calderón R et al. described in 2002 an "Exercise-induced anaphylaxis" after onion consumption.
• Occupationally induced allergies: Occupationally exposed cooks and greengrocers may have allergic rhinitis and bronchial asthma and protein contact dermatitis. Inhaled allergies have also been described in onion transport packaging.

Type IV reactions: However, contact reactions (see onion fingers below) are more frequent, especially in the case of occupational exposure (cooks). As with garlic, low-molecular organic sulfur compounds (diallyl disulfide) occur as allergens. Risk groups for contact allergies are cooks, housewives and vegetable sellers (Moyle M et al. 2004).

(Non-allergic) intolerance reactions caused by onion products:

• Intolerance reactions occur with severe flatulence or abdominal cramps. The fructans contained in the onion are responsible for this. Onions do not contain starch, but form and store fructans, high-molecular polysaccharides, as a reserve. These sulphur-containing polysaccharides are not broken down enzymatically in the small intestine in humans. They therefore reach the large intestine undigested and are metabolised there by the bacteria of the natural flora under strong gas development. After the consumption of onions, flatulence is therefore often caused by the odour of the sulphur-containing ingredients as well as the decomposition products of the fructans.

Prick and intradermal testing with commercial extracts, scratch with native material, RAST.

Epicutaneous testing: With 1% concentration of aqueous or ethanolic extract or expressed juice.

1. Antolin-Amerigo D et al (2012): Occupational allergy to Spanish omelet. J Investig Allergol Clin Immunol 22, 522-523
2. Asero R et al (2001): A case of onion allergy. J Allergy Clin Immunol 108: 309-310
3. Enrique E et al (2007) Involvement of lipid transfer protein in onion allergy. Ann Allergy Asthma Immunol 98: 202
4. Eriksson NE et al (2004) Self-reported food hypersensitivity in Sweden, Denmark, Estonia, Lithuania, and Russia. J Investig Allergol Clin Immunol 14:70-79.
5. Moyle M et al (2004): Use of gloves in protection from diallyl disulphide allergy. Australas J Dermatol 45: 223-225
6. Navarro JA et al (1995) Allium cepa seeds: a new occupational allergen. J Allergy Clin Immunol 96: 690-693
7. Pérez-Calderón R et al (2002) Exercise-induced anaphylaxis to onion. Allergy 57:752-753.
8. Valdivieso R et al (1994): Bronchial asthma, rhinoconjunctivitis and contact dermatitis caused by onion. J Allergy Clin Immunol 94: 928-930