Ask the Vet: Stay Out of Green Water!

Learn why it's important to keep an eye on your dog's favorite swimming spot.

Cyanobacteria, also known as blue-green algae, forms on the surface of a fresh water lake
PJ photography / Shutterstock

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Question: Kip, my retriever mix, loves to swim in a nearby lake, but the water recently turned green. Is it safe for him to swim?

Answer: I recommend you keep Kip from drinking or swimming in green water; the color may mean it’s contaminated with blue-green algae called cyanobacteria. Some species of cyanobacteria produce toxins that can sicken or kill animals and humans. Cyanobacteria live in both salt and fresh water and thrive in warm, calm water. When an animal ingests contaminated water, algae, or fish, toxins are released and quickly absorbed and circulated throughout the body, causing liver damage and neurotoxicity. Clinical signs can begin within minutes and include diarrhea, weakness, muscle tremors, paralysis, and seizures. Death can occur within a few hours.

Ask the Vet is written by veterinarian Lee Pickett, VMD. Send questions to [email protected] and read more at

This article is featured in the September/October 2020 issue of The Saturday Evening Post. Subscribe to the magazine for more art, inspiring stories, fiction, humor, and features from our archives.

Featured image: PJ photography / Shutterstock

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  1. I’m glad Kip’s pet parent asked you in advance about letting him swim in this lake recently turned green, Dr. Pickett. It doesn’t look healthy to me at all. It’s a shame because the dog really enjoyed himself prior to this. Hopefully the hazard(s) will be removed so Kip can safely swim in it once again.

    Even then, I’d have water samples checked by a reputable laboratory to ensure his safety and check with the authorities that oversee the lake. You never want to take an unknown risk if you can avoid it. Life has too many as it is we can’t foresee.


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