Anaphylactic reaction to probiotics. Cow's milk and hen's egg allergens in probiotic compounds

Background: Probiotics are used in the treatment of allergic diseases. We investigated the safety of probiotics for subjects with food allergy. Material and methods: Labels of probiotics commercially available in Spain were examined to assess their content of cows milk or hens egg. Skin prick tests with these compounds (20 mg/ml) were performed in five children allergic to cows milk, five children allergic to hens white egg, and five control subjects non-allergic to food. Three serum pools: I (positive-specific IgE to cows milk and hens egg white proteins), II (positive-specific IgE to cows milk and negative to hens egg white proteins), and III (negative-specific IgE to cows milk and positive to hens egg white proteins) were used to detect cows milk and hens egg white allergens in probiotics. ImmunoCAP (R) (Phadia), in-house ELISA, SDS-PAGE immunoblotting, and inhibition studies of these assays were performed. Proteins were quantified by enzyme-immunoassay. Results: Eleven probiotics were studied. No label advertised about egg content, eight labels warned about lactose, lactic acid or cows milk, one label claimed to be milk-free, and two gave no information. Cows milk proteins were detected, by at least one lab technique, in 10/11 probiotics, three over 2.5 mg/kg (21, 52, 112 mg/kg). Hens egg white proteins were detected in 3/11 probiotics, only one had more than 2.5 mg/kg (47 mg/kg). Conclusion: Probiotic compounds may contain hidden allergens of food and may not be safe for subjects with allergy to cows milk or hens egg.