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Marine Toxins


Marine toxins are chemicals and bacteria that can contaminate certain types of seafood. Eating the seafood may result in foodborne illness. The seafood may look, smell, and taste normal. There are five common types of marine toxins, and they all cause different symptoms.

Food poisoning through marine toxins is rare. Marine toxin poisoning occurs most often in the summer.

Diagnosing marine toxin poisoning

Your doctor will do a medical history and a physical examination and ask you questions about your symptoms and any fish you have recently eaten. Laboratory testing is typically not needed.

Treating poisoning

There are no specific treatments for marine toxin poisoning. Treatment generally consists of managing complications until the illness passes. Dehydration caused by diarrhea and vomiting is the most common complication.

To prevent dehydration, drink plenty of fluids. Choose water and other clear liquids until you feel better. You can take frequent sips of a rehydration drink (such as Pedialyte). Soda, fruit juices, and sports drinks have too much sugar and not enough of the important electrolytes that are lost during diarrhea. These kinds of drinks should not be used to rehydrate.

When you feel like eating again, start with small amounts of food. This will help you to get enough nutrition.

Preventing poisoning

Always keep seafood refrigerated or on ice. If you have a weak immune system, you should consider not eating raw seafood.

To help avoid marine toxins:

  • Do not eat barracuda, especially if it is from the Caribbean Sea.
  • Refrigerate fresh tuna, mackerel, grouper and mahimahi. Remember that cooking does not destroy the toxins in spoiled or toxic seafood.
  • Check with health officials about local advisories on algae blooms, dinoflagellate growth, or red tide.
  • Do not eat fish or shellfish sold as bait. These products do not have to meet the same standards as seafood for eating.

Types of marine toxin poisoning

Cooking does not destroy the toxins in seafood, so buy your seafood from a good source.

These are the types of marine toxic poisoning.

Scombrotoxic fish poisoning

  • This type is caused by bacteria. The bacteria may produce a chemical (histamine) that results in the foodborne illness.
  • It is usually found in finfish such as tuna, mackerel, and bonito.
  • It causes symptoms within an hour of eating the fish. The most common symptoms are rash, diarrhea, flushing, sweating, headache, and vomiting. Burning or swelling of the mouth, stomach pain, and a metallic taste may also occur. Most people have mild symptoms that are gone within 12 to 48 hours. In severe cases, antihistamines or epinephrine may be needed.

Ciguatera poisoning

  • This type is caused by ciguatoxins, which are produced by tiny sea plants called dinoflagellates.
  • It is usually found in tropical reef fish (such as barracuda) that kill other fish. But it may be found in grouper, sea bass, snapper, mullet, and other fish living in tropical waters. Common locations for these fish are the reefs surrounding Hawaii, the Virgin Islands, Puerto Rico, and Guam and other South Pacific Islands.
  • It causes symptoms within a few minutes to 3 hours. Symptoms include nausea, vomiting, diarrhea, cramps, excessive sweating, headache, and muscle aches. A feeling of burning and "pins and needles" as well as weakness, itching, and dizziness can occur. You may also experience unusual taste sensations, nightmares, and hallucinations. Symptoms usually are over in a few days to several weeks.

Paralytic shellfish poisoning

  • This type is caused by a dinoflagellate, although not the same one that causes ciguatera poisoning. These dinoflagellates have a red-brown colour and in large numbers can cause a red streak called "red tide" in the ocean.
  • It is usually found in shellfish in colder coastal waters, such as the Pacific Northwest and New England. Shellfish that have caused the condition include mussels, cockles, clams, scallops, oysters, crabs, and lobsters.
  • It usually causes symptoms within a few minutes to 4 hours of eating the shellfish. Symptoms usually begin with numbness or tingling in the face, arms, and legs, followed by headache, dizziness, nausea, and loss of coordination. Medical care may be needed if symptoms are severe. Some symptoms improve after 12 hours and can be over in a few days.

Neurotoxic shellfish poisoning

  • This type is caused by a type of dinoflagellate.
  • It is usually found in oysters, clams, and mussels from the Gulf of Mexico and the Atlantic Coast of the southern United States.
  • It causes symptoms in 30 minutes to 3 hours. They include numbness, loss of coordination, an upset stomach, and tingling in the mouth, arms, and legs. They usually last a few days.

Amnesic shellfish poisoning

  • This type is caused by toxins produced by a salt-water plant.
  • It is found in shellfish such as mussels.
  • It causes symptoms within 24 hours. Symptoms include an upset stomach, dizziness, headache, disorientation, and short-term memory loss. Seizures may occur in severe cases.


Current as of: October 31, 2022

Author: Healthwise Staff
Medical Review:
E. Gregory Thompson MD - Internal Medicine
Adam Husney MD - Family Medicine