A case of anaphylaxis caused by the health food chitosan

Chitosan is a linear polysaccharide with about 10(5)-10(6) molecular weight existing in cell walls of zygomycetes. Chitosan decreases serum neutral fat and cholesterol levels and has dietary fiber action, and many products have recently been sold as health foods. Here, we report a case of immediate-type allergy for chitosan-containing health food with a review of the literature. The patient was a 47-year-old female person who developed systemic urticaria and difficulty in breathing after oral ingestion of chitosan. Since skin tests (prick test and scratch patch test) were positive, the test was done using another commercial chitosan, and was positive. The patient was diagnosed as having chitosan-induced immediately-type allergy, and was instructed to avoid ingestion of chitosan. The patient has developed no symptom thereafter. Regarding allergic reactions to chitin and chitosan, contact dermatitis induced by chitosan-containing cream has been reported from France and Portugal, but to our knowledge, there has been no report of immediate-type allergic reactions. Chitosan is a polysaccharide, not protein, but may have functioned as a food allergen because of its molecular weight and general properties.