Is Blue-Green Algae Toxic to Dogs?

It’s a buzzword among the outdoor travel community, especially those who travel with their pets. But is blue-green algae toxic to dogs? Is this a serious concern or has it been blown out of proportion? In this post, we’re going to look at the basics of blue-green algae and dogs, when you should be concerned, and the most common symptoms of exposure. What should you do if your dog swims in blue-green algae? Read on to find out!

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What is Blue-Green Algae?

Blue-green algae is the common term used to describe cyanobacteria. These microscopic organisms grow naturally on the surface of water bodies like ponds, streams, rivers, and lakes. When the conditions are right, blue-green algae will grow to create an algae bloom. Ideal conditions include warm, calm, shallow bodies of water.

The formed algae blooms are often described as ‘paint-like’ in the way that they float on the surface of the water. But they can also form along the shoreline, on exposed rocks, or below the surface of the water. They are most often blue-green in colour, however, they can also be olive-green, greenish-brown, or even red.

While these microscopic organisms exist naturally and play an important role in the ecosystem, their growth has exploded in recent years.

This is often attributed to high levels of nitrogen and phosphorus entering the water from agricultural and storm runoff, septic system leaching, and even from using fertilizers in our own yards and gardens. When they grow to these high levels, blue-green algae can be harmful to the local wildlife, our pets, and even to ourselves.

The Difference Between Green Algae and Blue-Green Algae

While blue-green algae can be toxic, green algae serves a necessary role in the ecosystem as a source of food for fish, crustaceans, and other marine life. It can also be consumed by people and has long been part of Japanese cuisine.

Green algae will present with a bright or dark green colour. Unlike the paint-like appearance of blue-green algae, blending with the water, green algae is distinctly separate. It may appear like a large mat floating on top of the water or it can present with a stringy or silk substance.

One easy way to identify the difference is to dip a stick into the water. Blue-green algae will mix in with the water as if it is part of the water. Whereas green algae will drape over the stick allowing you to lift it from the water’s surface.

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Is Blue-Green Algae Toxic?

The most important question for dog parents: Is blue-green algae toxic to dogs? Not all blue-green algae are harmful or dangerous, but some can produce toxins. These toxins can cause health problems in people and animals when inhaled, touched, or swallowed. This most commonly occurs when swimming in local water bodies or taking part in recreational activities like boating, kayaking, canoeing, or fishing. But it has also been known to infect drinking water in areas where the water isn’t treated properly.

There is no way to identify if an algae bloom is toxic or not just from looking at it. This is why it is recommended that we avoid exposure entirely both for our safety and that of our pets.

Keeping your pets safe begins with learning how to identify blue-green algae as well as how to differentiate between blue-green algae and other forms of algae growth. While most algae will grow in stringy or distinguishable parts, blue-green algae is often described as looking like a paint spill or pea soup.

Blue-green algae also has a noticeable scent. When an algae bloom first forms, it smells like freshly mown grass. But, before long, it has an unpleasant rotten smell.

If you notice any of these signs in your local lake, river, pond, or body of water, it’s a sign to steer clear.

What Are the Side Effects of Blue-Green Algae?

Given the possibility of blue-green algae toxicity in dogs, it’s important to recognize if your dog has been exposed. But we don’t always notice if our dogs have been swimming in (or drinking) an infected body of water.

Here are some of the more common side effects of blue-green algae on dogs that you can watch out for:

  • Excessive panting or drooling
  • Vomiting
  • Diarrhea
  • Disorientation
  • Difficulty breathing
  • Liver failure and jaundice
  • Seizures

If blue-green algae exposure is not addressed, it can quickly turn fatal. If you notice any of these signs after your dog has been swimming or playing in a local body of water, get him to a veterinarian as soon as possible.

How Long Does Blue-Green Algae Take to Affect Dogs?

While the signs of blue-green algae toxicity will often show in as little as 30 to 60 minutes after being exposed, this isn’t always the case. In some cases, symptoms won’t show until anywhere from 12 to 24 hours. This is why it is so important to supervise your dog carefully after any water-related activities including canoeing, kayaking, paddle boarding, swimming, or even hiking alongside a local body of water.

Watch carefully for any signs of blue-green algae poisoning. If you are concerned or have any reason to believe that your dog has been exposed to blue-green algae, contact your veterinarian as soon as possible. The time it takes to bring your dog to treatment could determine whether he survives the experience.  

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Can Dogs Recover from Blue-Green Algae?

Is blue-green algae toxic to dogs and can your dog survive an exposure? If your dog has been exposed to blue-green algae, there is no antidote. But your veterinarian can provide supportive care, allowing the body to fight off the toxin.

Illness can happen very quickly after exposure. For this reason, it’s important to seek professional help as soon as possible. Your vet may be able to flush out the toxins but know that exposure can quickly turn fatal in dogs. Hospitalization and supportive care is your dog’s best chance.

What Do You Do if Your Dog Swims in Blue-Green Algae?

If you believe that your dog has been swimming in a body of water with blue-green algae, the first thing you should do is rinse him off thoroughly with fresh water. This will remove the algae from your dog’s fur before he has a chance to clean himself and ingest the offending contaminants. If you don’t have access to clean water for this process, baby wipes are a great choice. They come in small packages, making them easy to pack in your backpack for your next backcountry camping adventure.

Of course, the best ‘treatment’ is to prevent exposure before it ever happens. To do this, pay careful attention to the warnings posted at your local waterways before heading out. Consider calling the health unit to find out if any algae blooms have been reported in the area.

In addition to watching for the visual signs or the scents associated with blue-green algae, there are other red flags to watch out for. Pay attention when arriving at a hiking trail or dog beach for posted signage warning about unsafe water conditions. If you notice dead fish or birds along the shore, that is a clear sign to steer clear.

Returning to the original question, is blue-green algae toxic to dogs? It can be life-threatening. While this isn’t always the case, it’s not worth taking the risk. If you believe that your dog has been exposed to blue-green algae, seek help as soon as possible.

Have you ever encountered blue-green algae in your regular outdoor adventure areas? If so, let us know – especially if this is a recent risk!  


  1. This is such good information! I have never encountered blue-green algae that I know of, but I will for sure be on the look out for it. Thank you for sharing!

    1. It’s a growing risk in some areas. Even those that don’t live somewhere with blue-green algae problems (like we have here in Southern Ontario, Canada) should familiarize themselves just in case you travel somewhere where your dog may be exposed.

  2. This is such a great and informative post. I haven’t ever been around this kind of algae that I know of, but I will definitely look out for it in the future for sure!

    1. It’s definitely a risk that needs to be shared with anyone that enjoys spending time outdoors with their pets. All it takes is one exposure, as far too many pet owners have learned.

  3. I’ve heard a lot about blue-green algae, but know next to nothing about it. So thank you for providing that knowledge to plug that gap. What causes it to go from smelling like freshly moan grass to rotting garbage? At which stage does it potentially become toxic?

    1. Great questions – this is where things get a little difficult. The cyanobacteria known as blue-green algae can produce toxins during their lifespan, but they don’t always. Unfortunately, for that aspect, there is no way to tell without laboratory testing. Some testing kits have been made available to purchase online but they are very unreliable and not recommended by most experts. As for the smell, that occurs as the organisms die off and decay. This can also release toxins even in an algae bloom that wasn’t previously toxic, so that rotting smell is a big red flag!

  4. I can’t believe back in primary school we used to even lick those where water traveled. You mentioned that some of it can be toxic, makes me question why we made a decision to lick algae although I didn’t swallow. Dogs should be kept safe from this life-threatening thing. Thanks for sharing this, definitely learnt something new.

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