Red Tide (Paralytic Shellfish Poisoning)

What is red tide?

Red tide is a type of harmful algal bloom that happens in coastal waters. Harmful algal blooms happen when certain types of algae reproduce very quickly. Red tide will often turn the water red, but it can also give the water other colors or not change the color at all. In New England, red tide can happen during the spring, summer and fall.

The red tide that we get in New England does not affect the safety of the water—you can still swim in it—but the algae produce saxitoxin, a poison that gets into clams, mussels, scallops, oysters and other bivalve shellfish. The poison will not harm the shellfish, but people who eat the shellfish can get paralytic shellfish poisoning.

What are the symptoms of paralytic shellfish poisoning?

Paralytic shellfish poisoning can be very serious. It starts with numbness and tingling in your lips, mouth and throat. The numbness and tingling can spread to your fingers and toes and eventually make it hard to breathe.

It can also give you a headache, make you feel weak or make you feel sick to your stomach.

In some cases, paralytic shellfish poisoning can even kill you.

What should I do if someone has paralytic shellfish poisoning?

Call the Northern New England Poison Center at 1-800-222-1222, chat online or text POISON to 85511 if you think you have eaten shellfish harvested from a red tide area or if you are experiencing symptoms.

How can I prevent paralytic shellfish poisoning?

If there is red tide, state authorities will close shellfish harvesting in the area and put out a red tide advisory. Do not harvest or eat shellfish from a closed area. Cooking the shellfish will not make them safe to eat.

Stay safe by buying shellfish only from reputable fish markets and restaurants. If you harvest shellfish yourself, do not harvest in closed areas. You can get lists of areas closed because of red tide from the Maine Department of Marine Resources and the New Hampshire Department of Environmental Services.