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Blue-green algae (cyanobacteria)

Swimming in water contaminated with blue-green algae may cause symptoms of poisoning to people. Drinking water that is contaminated with blue-green algae or using it in cooking, for washing up, in the sauna or for bathing or washing may also cause symptoms of poisoning.

Suomalainen järvimaisema


In Finland, symptoms associated with blue-green algae have been mild. The most common symptoms include abdominal symptoms, skin symptoms and flu-like symptoms.

Nausea, vomiting, abdominal pain and diarrhea have been described as abdominal symptoms. Abdominal symptoms usually subside in a few days. Skin and flu symptoms develop more slowly and may last longer than abdominal symptoms. A rash, itching and stinging have been described as skin symptoms. Flu-like symptoms include a blocked or runny nose, a sore throat, a headache and fever. Blue-green algae may cause an eye or ear infection.


Wash the exposed areas with clean water and soap. Rinse the eyes with clean water. Care at home is usually sufficient for symptoms caused by blue-green algae. If necessary, use pain relief or an antipyretic drug. If the symptoms are severe and do not disappear within a week, contact a doctor. If you develop symptoms of an eye or ear infection, you should contact a doctor.