Urticaria Due To Natto (Fermented Soybeans)

Natto is a traditional Japanese food of fermented soybeans, in which Bacillus subtilis produces natto-mucilage as metabolic product. Different from soy allergy, natto-mucilage has been reported as a cause of natto-induced late-onset anaphylaxis occurring 5-12 hours after ingestion. Anaphylaxis was the primary clinical manifestation reported in natto-induced hypersensitivity. Here, we report that natto can cause urticaria as a sole symptom without developing into anaphylaxis.