Is it safe to swim? Blue-green algae: How to reduce the risks to humans and pets

Wisconsin Department of Natural Resources video on blue-green algae

The DOs and Don’ts of Harmful Algal Blooms

Image: WI Climate & Health Program Harmful Algal Blooms Toolkit, 2016

According to the Wisconsin DNR, there are additional measures you can take to PROTECT yourself, children, and pets:

  • Do not let children play with scum layers, even from shore
  • Do not treat surface waters that are experiencing blue-green algae blooms with any herbicide or algaecide– toxins are released into the water when blue-green algae cells die
  • Always take a shower after coming into contact with any surface water (whether or not a blue-green algae bloom appears to be present; surface waters may contain other species of potentially harmful bacteria and viruses)

The WI DNR also recommends several measure to help REDUCE future blue-green algae blooms:

  • Maintain native vegetation along shorelines as buffer areas
  • Minimize activities that result in erosion
  • Reduce the amount of fertilizer used on lawns
  • Use only phosphorus-free fertilizer when possible
  • Fix leaking septic systems
  • Use only phosphorus-free detergents in dishwashing machines

Interested in helping to improve water quality in the Winnebago Lakes? Get involved with Lake Management Planning by signing up for a project Focus Group. Click here to learn more.

Image credit: WI Climate & Health Program Harmful Algal Blooms Toolkit, 2016

Blue-green algae, also known as cyanobacteria, are responsible for harmful algal blooms and can cause adverse health effects for both humans and their pets. While not all blue-green algae produce harmful toxins, those that do can cause rashes, diarrhea, and respiratory problems.

Humans can be exposed to harmful algal blooms through accidental ingestion while swimming, by inhaling water spray (aerosols) during water recreation (such as boating), or by being in the water where a bloom is occurring. According to the Wisconsin Climate and Health Program, don’t go in if you are unsure about the water. If you come into contact with algal-affected waters, be sure to rinse yourself off immediately and get medical treatment right away if you think you have been poisoned by harmful algal blooms. (credit: Wisconsin Climate and Health Program)

“When in doubt, best keep out!”

What to do if your suspect exposure?

If you think you are experiencing symptoms from exposure to harmful algal blooms, contact your doctor or Poison Control Center (800-222-1222) right away. Call a veterinarian immediately if your animal shows any of the following signs of blue-green algae poisoning: lethargy, seizures, vomiting, diarrhea, convulsions, difficulty breathing, or general weakness. (Information source: WI Climate & Health Program Harmful Algal Blooms Toolkit, 2016)

Lots more information about blue-green algae can be found on the Wisconsin DNR website by clicking here.

Looking for Wisconsin DNR blue-green algae contacts? CLICK HERE

Pictures of Blue-Green Algae:

Photo credit: Rob McLennan, WI DNR

Article author: Korin Doering, Winnebago Waterways Program Coordinator, Fox-Wolf Watershed Alliance,

Content sources: WI Climate & Health Program Harmful Algal Blooms Toolkit, 2016; Wisconsin Department of Natural Resources Blue-Green Algae Webpage


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