Wilderness: Shellfish Poisoning, Paralysis

Medically Reviewed by Carol DerSarkissian, MD on October 02, 2024

Shellfish poisoning can occur after eating clams, mussels, oysters, scallops, cockles, starfish, and crustaceans that consume dinoflagellates during a red tide. During a red tide, sea waters turn a reddish color because large numbers of red organisms (dinoflagellates) are present. Dinoflagellates kill fish and other organisms by releasing toxins (poisonous substances). Consequently, shellfish take in the concentrated saxitoxin, a poison that causes paralysis.

Red tides are most common in the cold waters of North America, Europe, Africa, Asia, and Japan. A red tide rarely occurs in warmer climates. People are poisoned when they unknowingly eat shellfish contaminated during a red tide with saxitoxins.

Shellfish that is contaminated during a red tide does not have an abnormal taste, smell, or color, and the toxin is not destroyed by heating or cooking. Paralysis due to shellfish poisoning follows a similar progression to that of pufferfish poisoning.

Symptoms of shellfish poisoning begin 30 minutes to 2 hours after eating and include:

Muscle paralysis may occur. The person who has been poisoned may also develop the following conditions:

Ingesting large amounts of contaminated shellfish can result in coma and respiratory failure.

  • Do not induce vomiting
  • In case of vomiting, turn the person on their side to prevent the person from breathing in any stomach contents (vomit).
  • The person may become paralyzed.
  • Medical liquid charcoal to absorb the toxins may be given as a drink.
  • Artificial respiration may keep the person alive until they arrive at a hospital's emergency department.

Seek medical treatment as soon as possible.

wilderness: shellfish poisoning, paralysis; red tide; food poisoning; diarrhea; abdominal cramps; vomiting; nausea; toxicity

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