What are the health risks associated

with HABs?

Many species of blue-green algae produce chemical compounds that are toxic to warm-blooded creatures (people, pets, livestock, and wildlife), and some are toxic to other organisms like fish. The biggest risk to health comes from contact with or ingestion of the toxins produced by the blue-green algae bloom during activities that bring an individual into full body contact with the water (during swimming, skiing or jet skiing, for example), or from inhaling spray cast up from the water's surface, either by recreational activities or by the wind.

Children and pets are most at risk while engaging in recreation in the water because they are more likely to accidentally or intentionally swallow lake water. Pets can become ill after being exposed to spray. They can also become ill from eating dried algae along the shore or after licking affected water or algae from their fur. It is best to keep pets and children far away from exposures and move to safer locations. Adults with compromised immune systems are also more susceptible to illness from exposure.

These toxins can affect the liver, nervous system, skin, and other organs. The most common complaints after recreational exposure include vomiting, diarrhea, skin rashes, eye irritation, and respiratory symptoms. Blue-green algae (toxic and non-toxic varities) can also cause dermatological symptoms from prolonged skin contact with water or wet clothes. Some algal toxins are quite toxic and fast acting. Exposure to algal toxins can cause illness or possibly even death. No antidotes exist for any known algal toxins, and the compounds are not destroyed by boiling. This makes prevention the best option for protecting human and animal health during a bloom.


The following figure shows some of the potential symptoms from exposure to HABs.

Route of Exposure

Signs and Symptoms

Time to Symptom Onset

Differential Diagnosis

Hepatotoxins: Swallowing water contaminated with cyanobacteria or toxins

Elevated ALT
Acute hepatitis
Kidney Toxicity

minutes to hours

Other hepatotoxin poisoning, other microbial infections/toxins

Neurotoxins: Swallowing water contaminated with cyanobacteria or toxins

Motor weakness
Respiratory paralysis

minutes to hours

Pesticide poisoning, other toxic poisoning

Dermatotoxins: Skin contact with water contaminated with cyanobacteria or toxins or contact with animals

Itchy skin
Red skin
Skin blistering
Allergic reaction

minutes to hours

Other dermal allergens, non-allergic urticaria, photosensitivity reactions

Inhaling aerosolized droplets contaminated with cyanobacteria or toxins

Sore throat
Upper respiratory irritation
ossible allergic reaction

unknown, but likely an acute reaction

Other airborne allergens, upper respiratory infection, flu

Can HABs cause illness in animals?

Yes. State veterinarians have confirmed several cases of dog deaths due to harmful algal bloom toxins within the state of Kansas. When a HAB is present, pets should not be allowed near the shore where decaying algae may be visible. Ingesting enough toxin, either through drinking the water, licking the affected water or algae from their fur or paws, or eating the decaying algae, could lead to illness or death. Horses and cattle are also very susceptible to toxins due to the quantity of water they consume, and they should not drink water from ponds or lakes with a blue-green algae bloom. Pets and livestock should not be allowed in or near ponds or lakes with a blue-green algae bloom.

If a bloom is suspected, take the following precautions for your livestock and animals:

  • Train dogs to come to you for a drink of water and, carry potable water for your dogs when out hunting or going for walks along the shoreline.
  • Don't let your dog(s) retrieve waterfowl swimming in a waterbody affected by a HAB.
  • Move livestock to an alternate source of water.

What should I do if I accidently get water from a HAB on my skin?

Remove jewelry, watches, clothing, and other items that are in contact with the skin, and wash them thoroughly. Wash the affected area thoroughly with soap and water. Wash exposed clothing, keeping it separate from non-affected clothing. If rashes or other symptoms occur, seek medical attention immediately.

What if myself or my pets get ill and suspect it was from exposure to a


Please consult your physician or veterinarian immediately. Let them know exactly when, where, and how the suspected or known exposure occurred, and ask them to review symptoms. There are no antidotes to algal toxins, but there may be treatment options. Physicians and veterinarians are asked to report all human and animal harmful algae related illnesses to KDHE, but members of the public may do so as well. The KDHE Bureau of Epidemiology and Public Health Informatics (BEPHI) investigates reports of illness from a blue-green algae bloom exposure. If an illness complaint states that exposure occurred at a Kansas body of water that has not been sampled for HABs, BEPHI completes a blue-green algae bloom investigation request for the lake.

Illness reports can be submitted at:

Human Illness Form |

Animal Illness Form

Is it safe to go fishing and eat the fish I catch?

Where a HAB is present, avoid coming into contact with lake water as much as possible. Rinse fish with potable water prior to cleaning. Discard entrails and other body parts, and consume only the fillet portion. There have been some studies indicating that consumption of fish from lakes with high toxin levels should be limited, even if the consumption is of fillet only. In the case where a lake is posted as "Closed," fishing should not be allowed on the waterbody.

For more information...

See also the 2015 KDHE article, "Human Illnesses and Animal Deaths Associated with Freshwater Harmful Algal Blooms in Kansas"

For scientific research related to Harmful Algal Blooms and Health, see this special edition of the journal Toxins: "Harmful Algal Blooms (HABs) and Public Health: Progress and Current Challenges."

For additional resources, consult the following CDC documents:

  1. https://www.cdc.gov/habs/pdf/habsphysician_card.pdf
  2. https://www.cdc.gov/habs/pdf/habsveterinarian_card.pdf
  3. https://www.cdc.gov/habs/materials/factsheet-cyanobacterial-habs.html