What causes diarrhoea in dogs?

What causes diarrhoea in dogs?

Health & Safety

If there is one thing most of us wouldn’t wish upon our worst enemies, it would be coming home to find out that their dog has had diarrhoea. Not only is this thoroughly unpleasant to deal with and needs to be handled with great care to ensure good hygiene, but it will also be quite miserable for your dog too, and they may find diarrhoea painful and distressing as well as being unable to control their bowels.

Diarrhoea is something that most dogs will have a bout of at some point, and if you’re unlucky, more than once or even quite frequently.

The severity of diarrhoea in dogs can vary too, from a one-off minor anomaly to an acute, protracted bout, which can be highly uncomfortable for your dog and lead to dehydration and malnutrition.

However, diarrhoea is a symptom rather than a health condition in its own right, and so what causes it can be different from case to case. There are a number of different things that cause diarrhoea in dogs, and just knowing what they are can sometimes be enough to work it out for your own dog.

Knowing what causes diarrhoea in dogs is also the key to treating or resolving it too, or knowing if you simply have to wait it out; and that is what we will look at within this article.

Read on to learn the most common causes of diarrhoea in dogs.

Eating something that didn’t agree with them

By far the most common cause of diarrhoea in dogs is the dog eating something that didn’t agree with them, and many dogs are absolute idiots when it comes to eating first and thinking later! This doesn’t necessarily mean eating something that is outright toxic to them, but even something that is too rich, fatty, salty, or otherwise simply not designed for the canine digestive system; or even eating too much, or too fast.

Roadkill and discarded kebabs in the park are all likely to lead to a bout of diarrhoea if your dog manages to get their teeth into them!

Poisoning or toxicity

Poisoning and toxicity, being eating something poisonous or being exposed to something toxic can cause a range of symptoms in your dog, of which diarrhoea is just one of them. This is another potential cause of diarrhoea, as the body tries to eliminate the threat.

If your dog has eaten chocolate, for instance, which is very harmful for them, they might get diarrhoea, and if they only ate a very small amount of chocolate and are quite large themselves, this might be all that happens.

However, always contact your vet if you think your dog has ingested or come into contact with something toxic or poisonous, just in case.

Allergies and sensitivities

If your dog is allergic to something, this can cause diarrhoea. This is most common in the case of food allergies, but does not always involve something that your dog ingests.

Digestive sensitivities as opposed to outright allergies can result in diarrhoea too; such as if your dog drinks cow’s milk, as most dog’s bodies can’t handle the amount of lactose in it.

Stress and anxiety

Stress and anxiety are very common causes of diarrhoea in dogs, and this is something you should consider carefully when you’re trying to get to the root of the problem. A change of routine, feeling unsettled, and a number of other things can all be stressful for dogs, which might manifest as a digestive disorder like diarrhoea.


Viral or bacterial infections can all cause diarrhoea as one of their symptoms, such as parvovirus, which is serous, acute, highly contagious, and almost always fatal in puppies. It can also be vaccinated against!

A high worm count

If your dog isn’t wormed, doesn’t have an appropriate wormer, or comes into contact with a lot of wildlife (including eating roadkill) they can potentially develop such a high worm count that this results in acute digestive upset, including diarrhoea. This will almost certainly be accompanied by malnutrition.

Heatstroke or dehydration

Heatstroke and dehydration alike have a systemic effect on your dog’s body, and result in multiple signs and symptoms. Diarrhoea is just one of these, and so you have to take the wider picture into account too. Brachycephalic dog breeds like the French bulldog are at higher risk of developing heatstroke than others, so bear this in mind.

Internal blockages

If your dog eats a foreign object or swallows part of a toy and this cannot be digested or naturally passed out of the body via the digestive system, this can result in an internal blockage that in turn, can cause diarrhoea. A total blockage is acute and life-threatening, so if you know or suspect that your dog has swallowed something that might have caused a blockage or if they’re showing any related symptoms, contact your vet ASAP.

Bowel diseases

Finally, some diseases of the bowel can cause acute or recurrent bouts of diarrhoea in dogs too, and this is something you will need to consider if your dog frequently gets diarrhoea and you can’t assign the reason for this to any other obvious cause.

Inflammatory bowel disease is perhaps the most common of these; but all require veterinary intervention, so talk to your vet if you have any concerns about what is causing diarrhoea in your dog.

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