Urticaria due to natto (fermented soybeans)

Abstract

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.