Causes and Symptoms of Harmful Algal Bloom-Related Illness

On this page:
Symptoms
Duration of Illness
Exposure

Symptoms

Symptoms experienced during illness depend on the type of toxin present in the water and how a person is exposed (i.e., ingestion, skin contact, and inhalation).

Common symptoms experienced include:

• rash
• blisters
• cough
• wheezing
• congestion
• sore throat
• earache
• eye irritation
• diarrhea
• vomiting
• headache

Symptoms generally begin hours to 2 days after exposure to the toxins.

Duration of Illness

Symptoms typically last a few days in healthy persons.

Exposure

People can be exposed to microcystin and other cyanotoxins when surface scums or water containing high levels of toxins are:

• swallowed while drinking or recreating
• in contact with skin
• inhaled as airborne droplets while recreating or watering lawns and gardens

Although there have been no confirmed reports of cyanotoxin-related health effects due to eating fish caught during a harmful algal bloom, it is uncertain whether enough toxins in fish can be consumed to pose a health risk. 

Do you suspect you are experiencing adverse health effects from a harmful algal bloom? Visit reporting suspected foodborne/waterborne illnesses.