Case of scombroid syndrome mimicking an anaphylactic fish allergy.

BACKGROUND: Scombroid syndrome, a pseudo-allergic reaction caused by histamine-contaminated fish, is often mistaken for type I hypersensitivity reactions due to overlapping clinical presentations. Unlike IgE-mediated anaphylaxis, Scombroid syndrome results from histamine production by bacterial histidine decarboxylase in improperly preserved fish. It accounts for 5% of U.S. food poisoning cases and manifests within 30 min to two hours post-ingestion. CASE PRESENTATION: Symptoms include rash, pruritus, vomiting, and tongue swelling, as exemplified by a case of a 30-year-old woman misdiagnosed with anaphylaxis after consuming salmon. However, typically mild and self-limiting, severe cases may involve bronchospasm and arrhythmias. Diagnosis hinges on patient history, symptom onset, and absence of food allergy markers, such as elevated tryptase. Management includes antihistamines and supportive care; epinephrine and corticosteroids are reserved for severe reactions. CONCLUSION: Clinicians must distinguish Scombroid syndrome from anaphylaxis to ensure accurate treatment, emphasizing proper fish preservation to prevent outbreaks.