What Happens When You Eat Bad Fish?

WebMD explains that scombrotoxin poisoning is an allergic illness caused by the ingestion of spoiled fish. Symptoms include a burning sensation inside the mouth, dizziness, diarrhea, headache and an itching rash. Scombrotoxin can be treated with antihistamines, and its symptoms typically dissipate within four to six hours. Fish that are known to cause scombrotoxin poisoning include tuna, mahi-mahi and mackerel.

The Mayo Clinic explains that the bacteria in spoiled fish such as tuna can create a toxin that causes food poisoning symptoms that include vomiting, cramping and diarrhea. Since spoiled tuna can also cause scombroid poisoning, which is triggered by excess histamines and causes similar symptoms, it can be difficult to determine the difference between an allergic reaction or food poisoning. Allergic reactions typically cause additional symptoms, such as hives and wheezing.

According to MedlinePlus, Ciguatera poisoning is a common illness caused by eating fish that contain ciguatoxin, a poison created by algae. Ciguatoxin is heat-stable, which means that the toxin remains active regardless of how well the fish is cooked. Symptoms typically occur within 12 hours of ingestion and include cramping, severe diarrhea, headache, nausea and vomiting. Additionally, ciguatoxin causes a variety of uncomfortable sensations, which include a metallic taste in the mouth and the sensation of loose teeth. Ciguatera poisoning is treated with IV liquids and medications to relieve neurological symptoms.