Wisconsin health officials found pockets of blue-green algae "blooms" in the lake. Illinois health officials were out Thursday testing the water at lakes in north suburban counties.
The algae can produce toxic chemicals that can be harmful to humans and animals. To reduce the risk to the public, health officials have closed some beaches.
ABC7 Meteorologist Tracy Butler spoke Gina Laliberte with the Wisconsin Department of Natural Resources to discuss the potential risks of being in the water with the blooms.
"Some blue-green algae can make toxins. Not all do and those that do don't make them all the time," Laliberte said. "You would be exposed to those toxins, which could potentially make you sick, if you are swallowing them in water or if you are inhaling them in water drops."
Laliberte added that the toxic chemicals can also be harmful to pets.
"If they are drinking really questionable water that does contains blue-green algae they can become very sick. They can become exposed if they are licking blue-green algae off their fur too," Laliberte explained.
Meanwhile, there were a few boaters out on the lake in Wauconda Thursday afternoon, a lazy late summer day. Most were oblivious to the Lake County health department official taking water samples, testing the water quality.
Potentially toxic algae in Wisconsin lakes; Illinois water tested
Alana Bartolai with the health department is testing water for toxins which can come from algae. It's part of Lake County's regular testing program, and they also said algae is more of an issue this year because of the early season rains, followed by extreme heat
"Those are the ones that look like pea soup or if you spill pain in the lake that's more the blue-green algae that could contain toxins," Bartolai said.
Elevated levels of toxins from the algae have caused officials in Lake Geneva, Wisconsin to warn against swimming in the lake there. They were working to clear some of the algae today.
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Despite the health advisory in Wisconsin, on the Illinois side there are few beach closures to be concerned with. That was good news for paddle boaters like Myriam Brito.
"Tomorrow, I'm coming for a night paddle they have to watch the sunset and probably coming Sunday to paddle," Brito said.
The main danger from toxic algae comes from ingesting the water, and typically that can be dangerous for pets and young children.
Animals have trouble breathing, diarrhea, seizures and vomiting when exposed to the toxic chemical. Humans often experience a sore throat, congestion, diarrhea and eye irritation when exposed to the bloom.
"When we go to the vet, they recommend a shot to protect him from the water," dog owner Jennifer Hubbard said.
It will likely be several days before they get the results back from the testing done in Wauconda on Thursday, In the meantime, their lake is expected to be open for business over the weekend, and they're expecting a lot of business.
"Our motto is, 'when in doubt, stay out,'" Bartolai said. "If you're seeing a green scum area, stay away from that."
To report a blue-green algae-related illness, click here.
To see a map of beach conditions, click here.