Local health departments are alerting people to harmful toxins from blue-green algae blooms on Seminole County’s Lake Howell and Lake County’s Dead River south of U.S. 441.

The Dead River is a canal between Lake Harris and Lake Eustis.

You’re advised not to swallow the water or swim, wade or go boating in areas with algae. The water isn’t safe for pets, either.

Exposure to the toxins can cause rashes, stomach cramps, nausea, diarrhea and respiratory problems. Heavy exposure can affect the liver and nervous system.

Blue-green algae blooms become more common in Florida lakes during the summer and early fall. That’s when temperatures are high, days are long and storms flush nutrients into the water. 

And sometimes, as with these samples drawn last Wednesday, the algae produces harmful toxins.