Natto (fermented soybeans)-induced anaphylaxis in a surfer with the possibility of sensitization to poly(-glutamic acid) from cutaneous exposure to jellyfish sting: a case report

Background We report a case of anaphylaxis induced by natto (fermented soybeans) allergy that occurred following dermal sensitization from a jellyfish sting. Case presentation A 49-year-old male presented to the emergency room complaining of an acute onset of erythema with pruritis that appeared while he was surfing. Given that his heart rate dropped to similar to 40 bpm without a decline in blood pressure or oxygen saturation, we suspected anaphylaxis and administered 0.5 mg of adrenaline intramuscularly. Immediately after the muscular adrenaline injection, his heart rate recovered to similar to 60-70 bpm. Conclusions The major allergen that induces natto allergy is poly(gamma-glutamic acid) (PGA), which is present in its mucilage. Given that PGA is also produced by jellyfish tentacles, it can be inferred that the PGA sensitization occurred via dermal exposure to jellyfish PGA. This is an example of a food allergy induced by animal stings. As PGA is a high-molecular-weight polymer, natto allergy, despite being IgE-mediated, often presents with late-onset anaphylaxis, which typically develops half a day after digestion. PGA has a wide range of applications in pharmaceuticals, cosmetics, and foods. Patients may develop allergic symptoms and experience repeated anaphylaxis with no known cause. Therefore, it is important to obtain a detailed medical history and individually instruct patients suspected of being allergic to PGA to avoid PGA-containing products.