Scombroid Poisoning- NOT another fishy allergy

Scombroid poisoning (AKA – Histamine fish poisoning) is apparently more common than we think and accounts for 40% of seafood related illness in the USA according to the CDC. But Scombriod poisoning is missed as its put down to allergy.

How does it happen?

Approximately 75% of cases are linked to Tuna, but any brown fleshed fish can be responsible e.g. mackerel, anchovies

Scombroid poisoning is due to the production of Histamine through the decarboxylation of histidine in the muscle of the fish. The decarboxylation process is induced by enzymes produced by enteric gram-negative bacteria (e.g., M. morganii, E. coli, Klebsiella species and Pseudomonas aeruginosa).

Poor refrigeration or processing of the fish leads to the build-up of histamine within the flesh, so the patient may not be aware of the prior improper storage. Histamine is heat stable so cooking and freezing do not affect the concentration of histamine within the flesh, and has no smell so the patient may not notice anything amiss.


Symptoms usually start within 10-90 mins of ingestion and will present in a similar way to allergy

  • Skin: Itch Urticarial rash, Wheals, Flush, Erythaema
  • ENT: Burning mouth and throat
  • GIT: Cramps, Vomiting, Diarrhoea
  • Resp: Wheeze (rare)
  • CVS: Shock (rare)

Symptoms are generally self limiting rash will improve within 2-5 hrs, other symptoms can take 3-36 hrs.


  • Antihistamines – it is worth using both H2(Chlorphenamine) and H1(Ranitidine) antihistamines
  • Steroids and Adrenaline – are rarely indicated
  • Inform Public health – as this can be a significant breach in the food chain.



Canadian Medical Association: Scombroid poisoning


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