PupkeeperToxicEmergency
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, Australia, Canada, New Zealand
What to do now
- Call your vet or a pet poison line now.
- Rinse your dog right away with clean water to wash off algae.
- 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.
Signs 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
- CDC: Preventing Pet Illnesses Caused by Harmful Algal Blooms
- Pet Poison Helpline: Toxic Yard Items for Pets
- Royal Kennel Club: Dog Poisons Out and About
Guide reviewed 9 October 2026.
General information from the sources above, not a diagnosis. When in doubt, call your vet.