Scombroid fish poisoning

An 18-year-old healthy woman travelling in Thailand teleconsulted a dermatologist with a tingling tongue, paraesthesia of the lower lip, facial flushing, sweating, dizziness, palpitations and a skin rash, which developed 5 min after eating a tuna sandwich. She noted the tuna had a spicy taste. She had no previous history of atopy, food allergy, urticaria or angioedema. Examination showed facial oedema and a generalised erythematous rash (Figure 1a,b). Her co-traveller, who had taken a small bite from the same sandwich, felt slight tingling on the tongue, but developed no other symptoms. The typical history and presentation led to the diagnosis of scombroid fish poisoning. After taking oral antihistamines, symptoms resolved within the next few hours. Scombroid poisoning is an acute toxin-induced condition and is caused by the consumption of inadequately preserved or refrigerated fish (most commonly the Scombridae family, such as tuna and mackerel) that contains high levels of histamine.1 Enteric bacteria in the fish produce a decarboxylase enzyme that converts histidine to histamine, which is resistant to cooking, canning or freezing.2 Symptoms generally occur within 30 min after ingestion of the fish and commence with a tingling or burning sensation of the tongue that may be accompanied by a peppery, metallic or bitter taste. This can be followed by facial flushing, a generalised skin rash, palpitations, headache, dizziness, sweating, and gastro-intestinal symptoms like nausea, vomiting and diarrhoea. The likelihood of developing symptoms increases with the quantity of fish consumed.3 Scombroid fish poisoning can be distinguished from an allergic reaction as it may affect more than one person, as in our case, who often have no history of allergies. It is usually self-limiting, although antihistamines may be prescribed.1 Complications are rare and may require supportive care. Scombroid poisoning is often misdiagnosed as an allergic reaction leading to unnecessary anxiety, treatments and dietary restrictions. Public health authorities should be notified to explore potential sources and prevent further outbreaks. Marlous L. Grijsen and Raph L. Hamers were involved in the medical consultation of the patient, and jointly drafted the manuscript. Both authors reviewed and approved the final version of the manuscript. The authors thank the patient for granting permission to publish this information. The authors declare no conflicts of interest. The patient in this manuscript has provided written informed consent for the use of her de-identified anonymized data and her case details (including photographs) for publication. Ethical Approval: not applicable. Data sharing is not applicable to this article as no data were created or analysed in this study.