Food allergy to egg and soy lecithins

. Egg and soy lecithins are commonly used in the food industry as emulsi®ers (E322). The possibility of residual proteins leads to suspicion of their role in allergic manifestations in subjects allergic to egg or soy. Two cases are reported in which the double-blind, placebo-controlled oral challenge (DBPCOC), the ``gold standard'' of diagnosis, led to con®rmation that lecithin had caused lesions of atopic dermatitis (AD) in patients suffering from egg and soy allergies. E.G., a 15-month-old girl, presented with AD, progressive from the age of 2K months, as she was fed a milk formula. There was a family history of atopy (paternal pollinosis). The SCORAD was estimated at 26/103. Prick tests to ®ve inhalants were negative. Positive prick tests were obtained for egg white (10 mm) (codeine 9%=3 mm) and egg lecithin (3 mm) (negative in 61 patients allergic to egg), and RAST to egg was class 2 (CoopeÂrative Pharmaceutique FrancËaise, Paris, France). The labial challenge test (1) for egg white was positive, leading to exacerbation of eczema a few hours later, with an increase in the DBPCOC index from 26 at the start to 38/ 103. The DBPCOC to egg lecithin was positive at 50 mg, with the appearance of an erythematous rash on the neck and shoulders 1 h after ingestion. The second patient, G.S., a 4-year-old boy, with nonatopic parents, presented with asthma and AD. AD occurred at the age of 6 weeks and wheezing at 3 months. At around 1 year, the mother reported an episode of conjunctivitis complicated by angioedema in the eyelids immediately after ingestion of a small piece of peanut. A worsening of the asthmatic symptoms was noted after the age of 2 years. Strict avoidance of peanuts did not bring about satisfactory improvement. Prick tests were positive for Dermatophagoides pteronyssinus, birch and grass pollens, and peanut, with crossed sensitization to soy, but the prick test with soy lecithin was negative (Table 1), and RAST was 33.2 kU/l. The DBPCOC for peanut was positive at a total dose of 15 mg. The DBPCOC for peanut oil (6-ml dose) was also positive, causing an asthma attack. RAST for soy was 11 kU/l. The inhibition by soy lecithin rose to 62%. The DBPCOC at 100 mg of lecithin was positive, with the appearance of an erythematous rash on the jaw 1 h after ingestion. Protein assay of soy lecithin by the Kjeldahl method revealed a level of 3.5%, and of 11.3% in the egg lecithin. Lecithins are included in the excipients of certain drugs and/or lipidic emulsions used for parenteral feeding. Adverse reactions have been described, due to the inhalation of a bronchodilator with soy lecithins in the excipient, or to intravenous infusions (2, 3). In the food industry, asthma from soy lecithin inhalation has been reported (6). The level of soy lecithin in bread can be 0.015% (6). Many milk formulas including hydrolysates contain soy lecithin. Porras et al.'s study (6) con®rmed the presence of soy proteins in oil, margarine, and lecithin, and the allergenicity of these proteins was demonstrated in Awazuhara et al.'s study (7). RAST inhibition of 62% for soy, obtained by lecithin solution, con®rmed the allergenic nature of the residual proteins (3.5%). To our knowledge, we report the ®rst case of allergy to egg lecithin. The presence of lecithins in formulas, as well as in cookies and other foods, may explain why avoidance diets for soy and eggs that do not exclude lecithins yield only partial results. Therefore, we recommend that labeling be more precise.