The south shores of Lake St. Clair are under a blue-green algae bloom advisory.
The Windsor-Essex County Health Unit issued the warning on Friday, saying that people should avoid swimming if the water looks cloudy or like "green paint or pea soup."
"Infants and young children [under age six] should not swim or play in the water. For adults and children six years of age and older, they should swim with caution and rinse off after swimming," the health unit said in a media release.
Drinking water during an algae bloom could be fatal to pets.
Residents who use wells or cisterns that draw from that part of the lake should not drink the water unless a licensed lab finds the level of microcystins in the water to be below 1.5 parts per billion (ppb), the health unit said.
Microcystins are a toxin produced during blue-green algae blooms that can cause harm if the water is ingested or comes in contact with the skin. Children under six are most at risk, and the effects for those who come into contaminated water include skin and eye irritation.
If the water is ingested, small amounts can cause headaches, fever, and stomach symptoms such as nausea, diarrhea, and vomiting. In large quantities, ingesting the water could cause liver damage.