People may be exposed to these toxins through contact with the skin when swimming, inhalation when motor boating or water skiing or by swallowing contaminated water. Rashes, skin or eye irritation, and other uncomfortable effects such as nausea, stomach aches and tingling in fingers and toes may occur.

Swimming in water affected by cyanobacteria (blue-green algae) can lead to a range of unpleasant and potentially serious health issues. Contact with the skin often causes irritation, rashes, and "swimmer's itch." If you accidentally swallow the water or inhale the spray, you may experience gastroenteritis (vomiting and diarrhea), fever, headache, and sore throat. In more severe cases, high concentrations of cyanotoxins can cause liver or nervous system damage. In 2026, health authorities emphasize that children and pets are at the highest risk because they are more likely to ingest water while playing. If you suspect you've been exposed, the peer-to-peer "emergency step" is to rinse your skin thoroughly with clean, fresh water immediately and remove any affected clothing. If symptoms like confusion or severe abdominal pain occur, you should seek medical attention promptly.