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Are wild mushrooms harmful to dogs?

Ultimately, of course, it depends on the mushroom! However, with an increasingly warm and wet autumn climate, mushroom populations are soaring. In fact, this September the Veterinary Poisons Information Service (VPIS) actually issued a warning about the problem.

What is a mushroom?

This sounds really easy - but do you actually know what those bulbous masses are? Fungi are a kingdom of life all of their own, as different from plants as plants are from animals. Most fungi live in the environment and form networks of fine fibres growing through the soil. The mushrooms we see are their fruiting bodies, part of their reproductive cycle, which develop spores and then distribute them into the wind to spread where they will.

These fruiting bodies are high in protein and often very nutritious, so make a nice snack for any passing critter. Most fungi accept this as one of those things that, as a non-mobile fungus, one must put up with. However, there are a number that resent their unborn offspring being gobbled up by animals, and produce a range of really quite nasty poisons to deter peckish beasts.

What do mushrooms do to dogs?

The majority of the 4000 or so species of UK mushrooms are harmless - they might not taste nice, but they aren’t actually dangerous. However, there are a number that produce toxins called mushroom poisons (interestingly, although very similar poisons produced by moulds are called mycotoxins, the term is not usually used for those produced by the mushroom fruiting bodies themselves). For centuries, if not millennia, the properties of these fungi have been known by healers, botanists and shamens, and used for a range of uses (including religious ceremonies and to remove inconvenient members of the community… not that we recommend that at all!).

In dogs, we tend to see three groups of clinical effects:

Early onset vomiting and/or diarrhoea

These are usually the least harmful types of mushroom - as a general rule of thumb, the earlier the symptoms appear, the less dangerous the mushroom is. This is because it triggers vomiting and purging that remove any unabsorbed toxins from the dog’s system rapidly. If the dog is violently vomiting within six hours of eating the mushroom(s), then although they need to be seen by one of our vets (dehydration and salt imbalances from profuse vomiting can be dangerous in itself), the prognosis is usually fairly good.

Neurological effects

The most famous example is, of course, Psilocybe semilanceata, the “Magic Mushroom”, but there are a number of different psychoactive fungi in the UK. Unfortunately, dogs do not cope well with the effects of the active ingredients and may develop abnormal behaviour (well, of course!), self-injury, abnormal heartbeats and even seizures. In some cases, death may occur due to trauma while under the influence of the hallucinogen (for example, jumping from windows or running into solid objects), while in severe poisonings, the seizures may result in hyperthermia which may cause death from internal overheating (although fortunately this is relatively rare).

There are also species that can cause hallucination and other toxic effects, such as...

Liver and/or kidney damage

Sadly, many of the most dangerous mushrooms do not give easy tell-tail signs of poisoning until much later - possibly too late. These damage may damage the liver or kidneys, typically resulting in symptoms such as lethargy, depression, loss of appetite, increased thirst, increased urination (in kidney failure) and jaundice (in liver failure). Treatment requires intensive supportive therapy and often hospitalisation and the prognosis is guarded.

How do you know if a mushroom is safe or not?

The bottom line is that it’s very hard to tell - many harmless varieties have a poisonous twin that is almost indistinguishable. As a result, we strongly advise you not to let your dog eat wild mushrooms - full stop!

If you think your dog may have eaten an unknown wild mushroom, contact us IMMEDIATELY for advice.