Blue Green Algae Can Poison Your Pet (and You)

During summer months, especially after a rainy spring, city water departments will test lakes and ponds for the presence of blue-green algae. Blue-green algae can produce toxins that can be deadly to your pet. While it can affect people (and kids), birds, and livestock, dogs are especially at risk since they are very likely to be more immersed in lakes and ponds than other pets.

What Is It?

Cyanobacteria, sometimes called blue-green algae, are microscopic organisms found naturally in all types of water. The prefix cyano comes from the Greek word “kyanos” – a dark blue substance. Overgrowths of cyanobacteria can occasionally produce strong toxins know as cyanotoxins, which the Centers for Disease Control says are “among the most powerful natural poisons known.” These toxins can poison people, household pets, waterfowl and livestock.

What does it look like?

You cannot tell if a bloom is toxic just by looking at it. When a bloom occurs, scum might float on the water’s surface. Blooms come in different colors, from green or blue to red or brown. Sometimes, cyanobacteria produce toxins. The toxins can be present in the cyanobacteria cells or in the water. When in doubt, stay out.

What are the signs of Poisoning?

  • Liver toxins
    • repeated vomiting (green liquid)
    • diarrhea or tarry (bloody) stool
    • loss of appetite, anorexia
    • jaundice (yellowing of eye whites, gums)
    • abdominal swelling may be tender to the touch
    • cyanosis (bluish coloration) of skin
    • dark urine or reduced/ no urine output
  • Nerve toxins
    • stumbling, seizures, convulsions, paralysis
    • excessive salivation/drooling
    • disorientation, inactivity or depression
    • elevated heart rate, difficulty breathing 
  • Skin toxins
    • skin rashes, hives

Onset of signs can happen within 15 to 30 minutes

If you suspect your dog has been exposed to cyanobacterial toxins, seek immediate veterinary care.

How can you reduce the risk of dog poisoning by blue-green algae toxins?

  • Keep your dog on a leash near shorelines, and don’t let dogs wade, drink the water or eat/walk near the water’s edge.
  • If your dog goes in the water, remove them immediately.
  • Don’t allow your dog to lick their fur or paws after getting out of the water.
  • Rinse/wash them thoroughly with fresh water from a safe source if available. Otherwise a towel or rag can be used to remove algal debris.
  • Dry your dog thoroughly with a clean towel or rag.
  • Wash your hands with fresh water. The toxins are poisonous to humans too.



This blog post is based on material written by:

1. New York Sea Grant Dogs and Harmful Algal Blooms (HABs) publication. Funding for the development and printing of this publication was provided by the National Oceanic and Atmospheric Administration Center for Sponsored Coastal Ocean Research.
New York Sea Grant would like to acknowledge the following: Dr. Karyn Bischoff, Cornell University Veterinary College; Scott Kishbaugh, NYSDEC; Mr. John Wickham, NOAA National Ocean Service; Dr. Greg Boyer, SUNY ESF; Dr. Chris Gobler, SUNY Stony Brook School of Marine and Atmospheric Sciences (SoMAS); Dr. Lesley V. D’Anglada, USEPA; and Marti Martz, Pennsylvania Sea Grant Program.

2. Willem Becker, a veterinarian at Granite Veterinary Specialists
3. Centers for Disease Control and Prevention, Cyanobacter FAQ publicaton
4. Centers for Disease Control and Prevention, Animal Alert Flyer

© Harmony Veterinary Center 2019