Sub-navigation Navigation links - Current: Sub-navigation - [ Adder ](/en/patient/how-get-help/poison-information-center/adder) - [ Blue-green algae (cyanobacteria) ](/en/patient/how-get-help/poison-information-center/blue-green-algae-cyanobacteria) - [ Chemical products- information to manufactures and importers ](/en/patient/how-get-help/poison-information-center/chemical-products-information-manufactures-and) - [ Information releases and annual statistics ](/en/patient/how-get-help/poison-information-center/information-releases-and-annual-statistics) - [ Poison Information Centers Easter and May Day ](/en/patient/how-get-help/poison-information-center/poison-information-centers-easter-and-may-day) - [ The most poisonous mushrooms in Finland ](/en/patient/how-get-help/poison-information-center/most-poisonous-mushrooms-finland) - [ Adder ](/en/patient/how-get-help/poison-information-center/adder) - [ Blue-green algae (cyanobacteria) ](/en/patient/how-get-help/poison-information-center/blue-green-algae-cyanobacteria) - [ Chemical products- information to manufactures and importers ](/en/patient/how-get-help/poison-information-center/chemical-products-information-manufactures-and) - [ Information releases and annual statistics ](/en/patient/how-get-help/poison-information-center/information-releases-and-annual-statistics) - [ Poison Information Centers Easter and May Day ](/en/patient/how-get-help/poison-information-center/poison-information-centers-easter-and-may-day) - [ The most poisonous mushrooms in Finland ](/en/patient/how-get-help/poison-information-center/most-poisonous-mushrooms-finland) # 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.  ## Symptoms 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. ## Treatment 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. Updated: 23.09.2025 Print this page