NEWS: Harmful Algae & Swimmers Itch Reported in Montana

Many Montanans are looking for a way to cool off from the summer heat. Hitting the lake, rivers, or creeks sounds appealing after a day of 90-degree heat. However, you might want to reconsider where you take a dip. 

Harmful Algae blooms come around almost every year to Montana lakes. This year, it hit later than usual. Harmful algae blooms (HABs) are an accumulation of algae—a simple plant—in water and can cause adverse effects to humans and animals. HABs can happen for many reasons: hot weather, slow water flow, and weather events (drought, hurricanes, and flooding). However, we do contribute to HABs. An excess abundance of nitrogen, carbon, and phosphorus feeds algae causing it to grow and take over more of our lakes and streams. When you or farmers fertilize lawns or crops, extra fertilizer can get into our waterways, causing HABs. 

So far, the Department of Environmental Quality (DEQ) has issued caution warnings to Ennis Lake, Lake Helena, Hyalite Reservoir, Hauser Reservoir Causeway, Lake Elmo, and Canyon Ferry Reservoir. 

Swimmers itch has been reported in Bean Lake between Craig and Augusta. Swimmer’s itch is caused by microscopic parasites that cause swimmers to develop a rash all over their bodies. To avoid swimmer’s itch, don’t visit areas that have reported swimmers itch, avoid areas with lots of birds near or in the water, rinse off after swimming, and clean swimsuits frequently. In most cases, medical attention isn’t required. 

If you see something on the surface of the water looking like paint or pea soup floating in string-like groups, there is a chance it could be a harmful algae bloom. The colors of HABs can be green, red, and blue. You can report sightings on DEQ’s website

What would happen if you took a swim and did not notice the harmful algae? Ingesting the algae can be extremely dangerous. Symptoms can start immediately after exposure and possibly last two to three days. Some indications of Swimmers itch may include respiratory issues, abdominal pain, lethargy, diarrhea, vomiting, skin, throat, nose, eye irritation, paralysis, seizures, and tremors. These aren’t only pertaining to humans but dogs and livestock as well. If you see anything suspicious in the water, avoid the area and report what you see. 


Everyone should be aware of harmful Algae Blooms and Swimmers itch as they can cause problems for families out and about in Montana waterways this summer. Be cautious and report anything that looks suspicious.

Harmful Algae Bloom (HAB)

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