Those heading out to lakes and rivers this summer are reminded to be on the lookout for blue-green algae, also known as cyanobacteria, on water bodies across the state. Some blue-green algae can make toxins that cause illness in people and animals who accidentally swallow, inhale, or have prolonged skin contact with the algae.

"Blue-green algae are in all lakes and rivers in Wisconsin, but they only become a problem when they grow to high levels, called blooms," said Gina LaLiberte, DNR's statewide blue-green algae coordinator.

Blooms tend to grow when there is a lot of sunlight, water temperatures and nutrient levels are high, and there is little wind. In Wisconsin, blooms typically peak from July through September, though can also occur in June or later in the fall if conditions are favorable.

Actively growing blooms are usually green and have a "pea soup" appearance, but blooms may also appear as blue, white, red or brown scums that may be foamy, streaky or in mats or clumps.

While not all blue-green algae make toxins, the presence of blooms in lakes, ponds or rivers may indicate a potential health risk. Most beaches in the state are not currently monitored for blue-green algae, so it is important for the public to learn to assess water conditions for themselves.

"Choose the clearest water possible for small children and dogs, and avoid swallowing water that could contain other bacteria, viruses and parasites," LaLiberte said.

One easy way to identify potential risk from blue-green algae is for an adult to wade into knee-deep water. If they can see their feet clearly, the risk of acute illness is low to moderate for adults. If they can't see their feet, keep children and dogs out of the water. If people have any doubts about the appearance of water, they should stay out.

Public health officials also encourage people to shower off with clean water after swimming in any lake, pond or river. Dogs should always be rinsed off with clean water to remove algae from their coat.

According to the Wisconsin Department of Health Services, Division of Public Health, common symptoms of exposure to toxic blue-green algae blooms include skin rash, gastrointestinal illness and respiratory irritation. People experiencing symptoms that may be due to blue-green algal exposure should contact their health care provider or the Poison Center at 800-222-1222.

Animals have a higher risk of dying after exposure to blue-green algal toxins because they are smaller in size and may swallow large amounts of toxins from drinking lake, pond or river water or licking algae from their coat. Symptoms in dogs can include lethargy, loss of appetite, vomiting, diarrhea or even seizures. If your animal shows any of these symptoms, contact your veterinarian immediately.

People are also encouraged to report potential algae-related illnesses in both people and animals to the Wisconsin Department of Health Services by filling out the Harmful Algae Bloom Illness or Sighting Survey online or by calling 608-266-1120.

To help track the occurrence of blooms around the state, blooms may be reported to the DNR at