Blue-Green Algae in Water – Not Safe for Dogs or People

Author: Dr. Jason Nicholas

Published: August 4, 2015

Updated: June 23, 2021

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dog blue green algae water

For many dogs, summer often means swimming in lakes, rivers, or ponds. Along with the standard water safety steps (close observation, doggie PFDs, etc) and post-swimming ear cleaning to avoid ear irritation and infections, there’s something else you need to be aware of when you take your dogs swimming (or hiking, or camping near water) … blue-green algae.


Dangerous algal blooms are most common during periods of high heat.

Read along and tune in to this episode of the Paws & Play podcast to hear Dr. J talk about the dangers of blue-green algae:

Play Paws & Play episode Look Before You Swim: Blue Green Algae Toxicity Awareness
Paws & Play Look Before You Swim: Blue Green Algae Toxicity Awareness

Symptoms of blue-green algae toxicity

Dogs that drink water containing blue-green algae, or that groom the algae off their coat after swimming in such water, can exhibit a range of signs, including:

  • Uncoordinated walking (“Ataxia”)
  • Drooling
  • Vomiting
  • Diarrhea
  • Collapse
  • Seizures

If you’re noticing these signs in your dog, at any time, they need to be seen by a veterinarian right away. These are very serious signs indeed, and may well indicate liver failure from blue-green algae exposure.

blue green algae danger to dogs
Danger for dogs and people – lurking in ponds and lakes

Oh, and be aware, these algae aren’t just a problem for your pets — they can cause illness in children and adults, too! To find out if there are any blue-green algae warnings in your state, just google “blue-green algae (insert your state)” or check out these state-by-state resources: interactive map of state's blue-green algae labs and monitoring and state-by-state harmful algal bloom monitoring resources.

Using Technology to Combat Blue-Green Algal Blooms: Here's a great tool to help you and your pets (and other family members), as well as other people and their pets and families. Check out and download the bloomWatch app (available for both iOS and Android) to learn more about blue-green algae and to help pet owners, scientists, and others find and monitor these dangerous blooms. Citizen science at its best, and working for everyone!

Here are some really incredible photos of blue-green algal blooms courtesy of the USEPA and Cyanobacteria Monitoring Collaborative:

2020 JUL 16 Great Herring Pond MA - 1st documented bloom event - Photo Evie Saunders pic 1Blue Green Algae from USEPAMonponsett Pond-Ted broderick-Halifax-MAAlgae watch - Jon Samuelson Province Lake NH

You can also follow the social media feeds of CyanoTracker, a citizen science program out of the University of Georgia also focused on educating about, tracking, and combating blue-green algae. Here's CyanoTracker on Twitter, and CyanoTracker on Facebook.

About the author

Profile picture for Dr. Jason Nicholas

Dr. Jason Nicholas

Dr. Nicholas graduated with honors from The Royal Veterinary College in London, England and completed his Internship at the Animal Medical Center in New York City. He currently lives in the Pacific Northwest.

Dr. Nicholas spent many years as an emergency and general practice veterinarian obsessed with keeping pets safe and healthy. He is the author of Preventive Vet’s 101 Essential Tips book series.

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