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Blue-green algae (toxic algae) and dogs: what to do

Highly toxic. Toxic algae in lakes and ponds can kill a dog within hours of swimming in or drinking the water.

If your dog ate or touched this, call your vet or a pet poison line now

United States

Poison lines in other countries: United Kingdom, Canada, Australia, New Zealand, Belgium, France, JM, PR, Singapore, Switzerland, TT, VI

United Kingdom

Canada

Australia

New Zealand

Belgium

France

JM

PR

Singapore

Switzerland

TT

VI

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Blue-green algae (toxic algae) and dogs: key facts

Verdict
Toxic · Emergency: get help now
What it can do
Vomiting, diarrhea, drooling or foaming at the mouth, weakness or low energy and stumbling or falling. All 8
How fast
Within minutes to hours
What to do now
Call your vet or a pet poison line now. All steps
Sources
CDC, Pet Poison Helpline, Royal Kennel Club. Reviewed 9 October 2026.

What to do now

  1. Call your vet or a pet poison line now.
  2. Rinse your dog right away with clean water to wash off algae.
  3. Watch closely for a day or so; get to a vet at once if any signs appear.

Don't

  • Don't let your dog lick its fur before it has been rinsed.
  • Don't let your dog swim in, drink or play near water that looks scummy or discolored.
  • Don't let your dog eat dead fish or algae on the shore.

Symptoms to watch for

  • Vomiting
  • Diarrhea
  • Drooling or foaming at the mouth
  • Weakness or low energy
  • Stumbling or falling
  • Tremors or seizures
  • Trouble breathing
  • Yellow gums or eyes (jaundice)

When signs appear: Within minutes to hours

Why

Cyanobacteria (blue-green algae) make toxins that attack the liver or the nervous system. Blooms can look like pea soup, scum, foam or paint on the water.

Sources

Guide reviewed 9 October 2026. Page updated 7 November 2026.

General information from the sources above, not a diagnosis. When in doubt, call your vet.

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