Amnesic Shellfish Poisoning

Amnesic shellfish poisoning is a rare syndrome. It is caused by a toxin made by a tiny, salt-water form of algae. The toxin is found in shellfish, such as mussels. It causes disease when the unclean shellfish are eaten.


  • Patients first experience stomach distress within 24 hours after eating the unclean shellfish.

  • Other reported symptoms may include:

  • Dizziness.

  • Headache.

  • Disorientation.

  • Permanent short-term memory loss.

In severe poisoning, the following may happen:

  • Convulsions (seizures).

  • Paralysis.

  • Death.


Diagnosis of marine toxin poisoning is based on:

  • Symptoms.

  • A history of recently eating a particular kind of seafood.

If the leftover fish or shellfish is available, it can be tested for the toxin more easily. Knowing the specific toxin is not usually needed for treating patients. There is no specific treatment for each toxin. Treatment of those diagnosed with marine toxin poisoning primarily involves treating the symptoms.


General guidelines for safely eating seafood:

  • Keep seafood on ice or refrigerated to less than 38° F (1.1° C). This will prevent spoilage.

  • Keep fresh tuna, mackerel, grouper, and mahi mahi refrigerated to prevent development of histamine. Do not trust that cooking spoiled or toxic seafood will keep you safe. These toxins are not destroyed by cooking.

  • Do not eat barracuda, especially those from the Caribbean.

  • Check with local health officials before collecting shellfish. Look for Health Department advisories about algae blooms or "red tide" conditions. These may be posted at fishing supply stores.

  • Do not eat finfish or shellfish sold as bait. Bait products do not have to meet the same food safety regulations as seafood for human consumption.

  • Any person eating fish or shellfish containing toxin or disease-causing germs (bacteria) may become ill. Persons with weakened immune systems or liver problems should never eat raw seafood.


  • You develop problems that seem unusual for you after eating fish or seafood.

  • If the problems are severe, call your local emergency services (911 in U.S.).