Case 1: Rash and headache
Wednesday, December 8th, 2010This 34-year-old presented with a sudden onset of vomiting, headache and a bright red rash in the upper body (shown) while in a restaurant. Shortly afterwards he had watery diarrhea. He was generally healthy and had no history of food allergies. Over lunch he had peanuts, wine, a tuna steak and finished with strawberries.
1. What is the likely diagnosis?
Click to see the answerThis is scombrotoxin poisoning. This arises from eating dark fleshed fish from the scombroid family, including tuna, swordfish, bonito and others. The muscle of these fish contains large quantities of histidine as a buffer. If the fish is not kept properly after being caught, gram negative bacteriae convert the histidine into histamine. Such large quantities of histamine can be produced that it crosses the gut into the circulation, causing a headache, rash, vomiting and diarrhea. These symptoms normally pass in a few hours, and are unpleasant but not dangerous. Affected fish is said to have a metallic or peppery taste.
2. What is the treatment?
Click to see the answerAlthough antihistamines will block the effect of any absorbed histamine, there is rarely time to administer this. However if time permits, intravenous chlorphenamine, 10mg, would be appropriate.
3. What is the advice you would give for the future?
Click to see the answerThis condition is not thought to involve individual susceptibility, in the way that an allergy does. So the patient is not ‘allergic to fish’.