Blue-Green Algae and Dogs in the UK: How to Keep Your Dog Safe

9 hours ago
3 min read

Lakes and ponds can look like ideal places for dogs to cool down, but warm weather increases the risk of blue-green algae developing in UK waters.

Some types produce toxins that can make dogs seriously ill and may be fatal. Dogs should never swim in or drink from water where blue-green algae is present or suspected.

What Is Blue-Green Algae?

Blue-green algae is the common name for cyanobacteria. It occurs naturally in ponds, lakes, reservoirs and slow-moving rivers and streams.

During warm, settled weather, it can multiply and form a bloom. Not every bloom produces dangerous toxins, but owners cannot confirm whether water is safe simply by looking at it.

What Does Blue-Green Algae Look Like?

Possible signs include:

Green, blue-green or brown surface scum
Green flakes, clumps or streaks
Foam collecting around the water’s edge
Water resembling pea soup or spilled paint
Official warning notices beside the water

Blue-green algae is not always visible. Water that appears clear may still be unsafe, so follow local warnings and keep your dog out if you are uncertain.

How Can Dogs Be Exposed?

Dogs may swallow toxins by:

Drinking contaminated water
Swimming or playing in affected water
Fetching toys from the water
Licking contaminated water from their coat or paws
Eating algae or material washed onto the bank

A dog does not have to swim to be exposed, particularly when algae has collected near the water’s edge.

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Symptoms of Blue-Green Algae Exposure

Signs may develop quickly and can include:

Vomiting or diarrhoea
Excessive drooling
Weakness, drowsiness or collapse
Disorientation
Twitching or seizures
Difficulty breathing
Blood in the faeces

The symptoms and their severity can vary depending on the toxin and the amount swallowed.

What to Do If Your Dog Is Exposed

If your dog may have entered, drunk from or licked water containing blue-green algae, contact a veterinary practice immediately. Do not wait for symptoms to appear and do not try to make your dog vomit unless a vet specifically instructs you to do so.

Move your dog away from the water and prevent it from licking its coat. If it is safe, wear gloves and rinse the coat thoroughly with clean water, taking care to avoid direct contact with the contaminated water. Do not allow rinsing to delay urgent veterinary advice or treatment.

Tell the vet where the exposure occurred, approximately when it happened and what your dog did in the water. A photograph of the water or warning sign may be helpful, but never put yourself at risk to obtain one.

How to Protect Your Dog

Check for warning notices before approaching the water.
Keep your dog on a lead around water that may be affected.
Carry fresh drinking water on walks.
Do not throw toys into unfamiliar ponds, lakes or rivers.
Use a clean paddling pool at home as a safer way to cool down.
Rinse your dog with fresh water after outdoor swimming.
Never enter dangerous water to rescue a dog; call the emergency services.

Open water may also contain strong currents, steep banks, submerged objects and other hidden hazards. Even confident canine swimmers can get into difficulty.

How to Report Suspected Blue-Green Algae

Suspected blooms can be photographed and reported through the UK Centre for Ecology & Hydrology’s Bloomin’ Algae app. You can also alert the landowner, park authority or local council so the water can be assessed and other visitors warned.