The Full Story
What you can't smell can't hurt you, right? Wrong! Eating some kinds of spoiled fish can cause dramatic symptoms.
Common types of poisoning from spoiled fish include scombroid and ciguatera. Neither type of fish poisoning can be detected by taste or appearance. Neither can be prevented by cooking or freezing the fish. Fish can also be contaminated with chemicals or heavy metals.
Scombroid poisoning is caused by fish which have not been refrigerated properly from the time they were caught until the time they were served. Bacteria act on compounds in the fish, releasing histamine. This accounts for the allergic-type symptoms and also explains why antihistamines help control the symptoms. The fish most often responsible include tuna, mahi-mahi, mackerel, marlin, bluefish, amberjack, and abalone, though many others have caused scombroid poisoning.
A person who catches his or her own fish must be careful to keep the fish refrigerated at all times, at a temperature no higher than 40 degrees F. There is no other reliable way to prevent scombroid poisoning. In a restaurant or store, it is impossible to know for sure if a fish has been properly stored during its entire journey from the water. Scombroid generally is not detectable in fish, but if fish taste peppery or burning, do not eat them. If anyone develops symptoms of scombroid from fish from a store or restaurant, be sure to let the facility and the health department know. That might prevent someone else from becoming ill from eating the same fish.
Symptoms of scombroid fish poisoning begin quickly, within about 15 minutes to 2 hours. Most people experience some combination of flushing and rash on the face and upper body, sweating, diarrhea, and abdominal cramps. Sometimes, there is a burning, peppery taste in the mouth. Most people recover quickly without treatment. More serious symptoms of breathing trouble, swelling of the tongue and mouth, and blurred vision, require treatment in an emergency room with antihistamines, such as diphenhydramine (Benadryl®) and perhaps other drugs.
Ciguatera fish poisoning causes nausea, vomiting, diarrhea, muscle weakness, joint aches, headache, dizziness, and low blood pressure. A characteristic symptom is "hot-cold reversal"; hot items feel cold and cold items feel hot. Symptoms may begin within 15 minutes to 24 hours after eating affected fish. Most people are better in a few days, but in some cases symptoms have lasted for months or even years.
Ciguatera is produced by a type of algae associated with coral reefs. Small plant-eating fish eat the algae, are eaten by larger fish, again by yet larger fish, and on up the food chain. More than 400 species of fish are known to have caused ciguatera poisoning, but the most common are older, larger fish which have been eating contaminated fish during their life spans: grouper, barracuda, snapper, jack, mackerel, triggerfish, and others. Even though contaminated fish are from tropical and sub-tropical fish, ciguatera poisoning occurs anywhere these fish are shipped for food. There is no specific prevention except to eat fish smaller than about 4-6 pounds. Treatment is based on symptoms.
Spoiled fish, the result of poor food handling practices, can also cause dramatic gastrointestinal symptoms – nausea, vomiting, diarrhea, and abdominal pain. As with any other perishable food, fish need to be handled safely: keep uncooked fish cold, keep cooked fish hot, wash hands, utensils, and cutting boards before and after handling raw fish.
For questions about fish poisons, or if you think someone is having a reaction to fish, call Poison Control. Poison specialists are available 24 hours a day at 1-800-222-1222.
Rose Ann Gould Soloway, RN, BSN, MSEd, DABAT emerita