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Histamine fish poisoning: a common but frequently misdiagnosed condition
  1. R R Attaran,
  2. F Probst
  1. Accident and Emergency Department, Guy’s and St Thomas’ NHS Trust, London, UK
  1. Correspondence to:
 Dr F Probst, Accident and Emergency Department, St Thomas’ Hospital, London SE1 7EH, UK


Scombrotoxic or histamine fish poisoning is a common condition normally associated with consuming spoiled tuna, mackerel, bonito, or skipjack. Typical symptoms like flushing, urticaria, and palpitations mimic those of allergy so histamine fish poisoning can easily be misdiagnosed. Diagnosis is often clinical and the mainstay of treatment is antihistamines.

  • histamine fish poisoning

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A 37 year old woman presented to accident and emergency (A&E) having consumed yellow-fin tuna. Within 20 minutes she had developed an urticarial rash on her face, neck, and trunk with chest tightness. She had no history of hypersensitivity and normally consumed tuna on a weekly basis.

On arrival she was tachycardic and tachypnoeic, had mild facial angio-oedema but no wheeze. She was seen immediately by a registrar who diagnosed a hypersensitivity reaction and administered intramuscular adrenaline (epinephrine), intravenous hydrocortisone, and chlorpheniramine.

The patient’s symptoms improved within 30 minutes and after a further six hour observation period, was discharged home on a short course of oral corticosteroids.

The patient subsequently underwent a RAST (Radio Allergic Sorbet Test) to various potential culprits including tuna, all of which were negative.


Four men and one woman (mean age 32; range 25 to 42) arrived together at A&E having all consumed tuna at a restaurant. About 15 minutes after ingestion all had begun to experience generalised urticaria, palpitations, and felt hot. None had a history of urticaria or hypersensitivity.

On arrival three of five patients were tachycardic and tachypnoeic. Erythema was noted over all their faces and trunk. The concurrent presentation of five such cases to A&E roused the suspicion of the attending registrar who diagnosed histamine fish poisoning.

All were treated with the antihistamine chlorpheniramine orally with symptoms resolving within two hours. One required nebulised bronchodilators.


A 27 year old woman presented an hour after consuming tuna at home. She had eaten from the same batch two days previously, when she had developed some urticaria and flushing but they had resolved within three hours. On the second occasion her symptoms had been more pronounced and included chest tightness and angio-oedema of the lower lip.

The patient was treated for hypersensitivity. Intravenous hydrocortisone, chlorpheniramine, and fluids were administered. The patient was discharged later the same day after resolution of symptoms. Again this patient had no history of hypersensitivity to tuna or any other seafood.


Scombrotoxic or histamine fish poisoning (HFP) is a common seafood-borne disease. Between 1992 and 1999, 10% of the infectious intestinal disease outbreaks reported to the Communicable Disease Surveillance Centre were associated with fish, about half of those to HFP.1 It is the most common cause of seafood poisoning in the USA.2 A variety of factors, including misdiagnosis, result in its underreporting.3

Key points

  • Common though frequently missed.

  • Normally associated with tuna.

  • Not an allergic reaction but features similar to allergy.

  • No prior or subsequent reaction to the fish.

  • Treated with antihistamines.

  • Notifiable.

Spoiled oily fish of the families Scombridae and Scomberesocidae (especially tuna, mackerel, bonito, and skipjack) are common but not the only culprits.4 In these fish, bacterial histidine decarboxylase converts muscle histidine into histamine.5,6 Bacterial activity is increased at raised temperatures so poor storage conditions exacerbate the problem.7 Cooking can destroy the bacteria but not the histamine.8 The gradual build up in toxicity of spoiled fish could be demonstrated by case 3 where a 48 hour period separated a mild from a severe reaction.

Whether HFP is purely a result of histamine effect is unclear.4,9–11 None the less, signs and symptoms are essentially those of histamine toxicity: flushing, urticaria, abdominal cramps, headache, palpitations, diarrhoea, nausea, and vomiting.12–15 These can begin within minutes of ingestion and typically last several hours.12,16

Diagnosis is often clinical, though the fish specimen can be assayed for histamine levels. The patient will typically have not had a reaction to that fish before. In a group of people consuming the contaminated fish, more than one person will probably be affected, perhaps all.15 Skin allergy testing using fresh samples from the same fish can help exclude hypersensitivity.

The treatment of HFP is not too different from that of a hypersensitivity reaction. Symptomatic relief can be achieved by the use of antihistamines such as H1 and H2 histamine receptor antagonists.4,16,17 Occasionally salbutamol and adrenalin may also be warranted. Corticosteroids are generally not indicated.18

In October 2001 alone, four such episodes of HFP were seen in the St Thomas’ Hospital A&E Department, three of which have been reported here. In all but one (case 2) the diagnosis was missed.

HFP is a common self limiting condition sharing features with that of allergy, such as flushing, urticaria, and palpitations. Physicians must be aware of HFP as it is notifiable to the local Communicable Disease Centre and patients can be reassured that they have probably not had an allergic reaction.