Wilderness: Shellfish Poisoning, Paralysis

Shellfish Poisoning Paralysis Overview

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.

Shellfish Poisoning Paralysis Symptoms

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.

Shellfish Poisoning Paralysis Treatment

  • 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.

When to Seek Medical Care

Seek medical treatment as soon as possible.

Synonyms and Keywords

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

WebMD Medical Reference Reviewed by Jennifer Robinson, MD on August 29, 2020



Author: Scott H Plantz, MD, FAAEM, Research Director, Assistant Professor, Department of Emergency Medicine, Mount Sinai School of Medicine.

Editors: N Stuart Harris, MD, MFA, Staff Physician, Department of Emergency Medicine, Harvard Medical School; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; James Kimo Takayesu, MD, Staff Physician, Department of Emergency Medicine, Brigham and Women's Hospital/Massachusetts General Hospital.

CHC Medical Library and Patient Education: "Fish and shellfish poisoning."

SailNet: "Dangerous Seafood."

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