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Blue-Green Algae Poisoning in Dogs

algae poisoning in dogs

During algal blooms in lakes, seas, and watercourses, a poison can form in the water. If a dog bathes in or drinks the water, it can suffer from algae poisoning, which is a life-threatening condition. Here you can read more about what algae poisoning is, what symptoms to be aware of, what to do if you suspect poisoning, and what you can do to prevent your dog from coming into contact with poisoned water.

What is Blue-Green Algae, and why is it important?

Blue-Green Algae, also known as Cyanobacteria, is a group of plants that produce toxins. These toxins can poison animals (and people) when they swallow, swim in, or inhale affected water or when they eat fish from these waters. Algae can be simple plants of a microscopic size or large plants such as seaweed. Although most algae are harmless and part of a balanced ecosystem (both in salt and fresh water), overgrowth is what leads to toxicity.

How and why does this happen?

Toxins are produced when the weather is warm and sunny, causing an overgrowth and harmful algal blooms. Harmful Algal Blooms (HABs) are also known as “red tide”, which often affects coastal waters, but can occur anywhere in the world. Changes in the water can lead to an increased amount of nitrogen and phosphorous, which causes the algae to grow faster. Besides sunlight and warm weather, human activity seems to be causing more HABs to grow, more often, and more severe (ex: fertilizer washed into a lake by rains causing an increase in nutrients).

What do toxic algae look like? When does it occur?

Water will turn red, brown, yellow, and/or green depending on the species of algae, and often there is scum or a film on the water’s surface. HABs are more likely to occur in the warm months of Summer and early Fall.

By using up oxygen and blocking sunlight from other life in the water, they are threatening to plants, animals, and people. The toxins from the algae will kill some fish but accumulate in other fish and shellfish causing people (or animals!) who eat these, later on, to become ill. This is known as Neurotoxic Shellfish Poisoning (NSP) and Ciguatera Fish Poisoning, respectively.

Clinical Signs of Blue-Green Algae Poisoning in Dogs

Swimming in affected waters can irritate the eyes, nose, and throat, rashes, and skin irritations. Breathing in HABs can cause coughing, irritation of the lungs, and can worsen asthma.

Swallowing the affected water can cause vomiting, diarrhea, black tarry stool, liver damage or failure, pain in the abdomen, weakness, seizures, muscle tremors, paralysis, disorientation, coma, shock, and death. Sadly, many animals die quite quickly after drinking water with HABs, making it difficult or impossible to get them to a vet in time. Wildlife can be found deceased by the sides of affected lakes. Even just a few laps of water by the side of the lake can be fatal, and quickly.

Treatment Option for Dogs with Algae Poisoning

There is no specific antidote for blue-green algae toxicity, but supportive care is imperative immediately. If your pet is somehow exposed to harmful algal blooms, IMMEDIATELY wash with soap and water, and contact one of the Animal Poison Control centers at 1-888-426-4435 or 1-855-764-7661 while you drive to the closest veterinary hospital.


Don’t forget to also call human poison control (1-800-222-1222) if you have been exposed as well. You can help out by reporting any affected water to your local health department as soon as you can. You may be able to save a life!

Preventing Blue-Green Algae Poisoning

  • Avoid contact with water that is discolored or has scum or film floating on its surface
  • Do not let pets drink from such water
  • Do not let pets play or swim in such water
  • Do not eat fish or feed fish to your pets from such water
  • In general, it is good advice to never give your pet (or yourself) untreated water from lakes, streams, or rivers

Read more:

16 Summer Dangers for Dogs

What’s Wrong with My Dog’s Tail? Facts About Limber Tail Syndrome

What plants are toxic to dogs?

Need to speak with a veterinarian regarding blue-algae poisoning in dogs or another condition?
Click here to schedule a video consult to speak to one of our vets. You can also download the FirstVet app from the Apple App Store and Google Play Stores.

*If you suspect your pet has been exposed to toxic algae, call Animal Poison Control, and take them to the vet immediately!*

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