Paralytic shellfish poisoning (PSP) is the most common and most severe form of shellfish poisoning. PSP is caused by eating shellfish contaminated with saxitoxins. These potent neurotoxins are produced by various dinoflagellates. A wide range of shellfish may cause PSP, but most cases occur after eating mussels or clams. PSP occurs worldwide but is most common in temperate waters, especially off the Pacific and Atlantic Coasts of North America, including Alaska. The Philippines, China, Chile, Scotland, Ireland, New Zealand, and Australia have all reported cases. Symptoms usually appear 30–60 minutes after eating toxic shellfish and include numbness and tingling of the face, lips, tongue, arms, and legs. There may be headache, nausea, vomiting, and diarrhea. Severe cases are associated with ingestion of large doses of toxin and clinical features such as ataxia, dysphagia, mental status changes, flaccid paralysis, and respiratory failure. The case-fatality ratio is dependent on the availability of modern medical care, including mechanical ventilation. The death rate may be particularly high in children.

Saxitoxin Poisoning is monitored to prevent and control outbreaks.

In 2023, the number of Saxitoxin Poisoning (Paralytic Shellfish Poisoning) in Alachua County was compared to Florida at . The line graph shows change over time when there are at least three years of data.