Causes and Symptoms of Harmful Algal Bloom-Related Illness - Minnesota Dept. of Health

Causes and Symptoms of Harmful Algal Bloom-Related Illness

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Duration of Illness


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.


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.

Updated Tuesday, 29-Jan-2019 16:25:15 CST