introduction

Autumn arrives, the first rains fall and the countryside fills with new smells. For your dog, every walk becomes an adventure: leaves, damp soil, traces of other animals… and also mushrooms, acorns and chestnuts within reach of its nose. Dogs explore the world with their nose and, sometimes, with their mouth, so it is worth knowing what could make them ill.

toxic mushrooms, acorns and chestnuts: an autumn guide

In this complete guide we explain, in plain language but with a technical basis, which toxic mushrooms for dogs you should know about, what happens with acorns and chestnuts, which signs to watch for and how to act if your dog eats something off the ground. The good news is that, with a little information and a few simple habits, you can keep enjoying the countryside together with complete peace of mind.

which mushrooms are toxic to dogs?

Let’s start with a reassuring fact: not every mushroom a dog eats is dangerous. A study by the Norwegian Poison Information Centre, which analysed 421 cases of dogs that had eaten mushrooms, found that in 45% of cases the mushroom was not toxic, and that most of the toxic ones only caused digestive problems (Seljetun and Kragstad, 2023). Even so, some mushroom species can cause severe poisoning (Puschner and Wegenast, 2018), and there is no reliable way to tell a poisonous mushroom from an edible one at a glance: many can be confused with each other, even by experienced people.

These are the toxic mushrooms worth knowing about, grouped by the part of the body they affect:

Mushrooms that affect the liver: Amanita phalloides

Amanita phalloides, or death cap, contains amatoxins. These toxic substances prevent liver cells from making the proteins they need to function, so the organ is gradually damaged. Other small mushrooms, such as some Lepiota species or Galerina marginata, contain the same toxins (Puschner and Wegenast, 2018). Young dogs, being curious, are the ones that taste mushrooms most often, so they deserve special attention (Tegzes and Puschner, 2002).

Mushrooms that affect the nervous system: Amanita muscaria and Amanita pantherina

Amanita muscaria, the classic red mushroom with white spots, and Amanita pantherina contain ibotenic acid and muscimol. These substances resemble the chemical messengers the brain uses to communicate, which is why they disrupt how it works. The dog may appear disoriented, stagger, tremble or be very drowsy (Romano et al., 2019). Their effects usually show early and, with prompt veterinary care, the overall prognosis for mushroom poisoning in dogs is good (Seljetun and Kragstad, 2023).

Mushrooms that affect the kidneys: Cortinarius

Some species of the genus Cortinarius contain orellanine, a toxin that builds up in the kidney and damages the cells responsible for filtering the blood. What makes it special is that it acts slowly, and signs can take quite a while to appear (Puschner and Wegenast, 2018). Keep an eye on whether your dog drinks or urinates more or less than usual in the days after the walk. If you notice any change of this kind, your vet can assess kidney function with a simple blood test.

Mushrooms that affect the glands and the digestive system: Inocybe and Clitocybe

These fungi contain muscarine, which is why they are called “muscarinic”. Muscarine mimics a natural substance in the body that activates the glands and slows the heart. The result is easy to recognise: heavy drooling, watery eyes, vomiting and diarrhoea. Their effects also appear soon after ingestion, which makes it easier to act quickly (Puschner and Wegenast, 2018). In the Norwegian study, they were the second most common group of toxic mushrooms (Seljetun and Kragstad, 2023).

symptoms of mushroom poisoning in dogs

The symptoms of poisoning depend on the species, the amount eaten and the size of the dog. These are the most common signs:

• Vomiting and diarrhoea.
• Abdominal pain: the dog hunches over, is restless or does not want its belly touched.
• Excessive drooling and lethargy.
• Staggering, tremors or disorientation.
• Yellowish gums or eyes, a sign of liver problems.

There is one important detail: mushrooms that affect the liver act slowly. In a study with beagle dogs, the first digestive symptoms appeared between 12 and 24 hours after ingestion (Sun et al., 2018). In other words, the fact that your dog seems fine after eating a mushroom does not mean it has not been affected. That is why the most useful thing is to call your vet as soon as you find out, without waiting for signs to appear.

my dog has eaten a mushroom: what to do

If your dog has eaten a mushroom, or you suspect it may have, stay calm and follow these steps:

1. Remove whatever is left in its mouth, taking care not to get bitten.
2. Call your vet, even if your dog seems fine. Outside opening hours, contact an emergency service.
3. Keep a sample of the mushroom, ideally whole, in a paper bag or wrapped in kitchen paper (plastic speeds up its deterioration). If you cannot pick it up, take photos of the cap, the gills and the stem.
4. Note the approximate time of ingestion and any changes you observe.
5. Do not induce vomiting at home or give home remedies (hydrogen peroxide, salt, milk): they can cause injuries.

At the clinic, if ingestion was recent, the vet can safely induce vomiting and give activated charcoal, a powder that traps toxins in the intestine so they do not pass into the bloodstream. They will then assess whether blood tests or fluids are needed. Speed makes the difference, and the results are very encouraging: in the Norwegian study, 98.6% of dogs survived, and the authors highlight how useful it is to identify the mushroom correctly from the start (Seljetun and Kragstad, 2023).

are any mushrooms safe for dogs?

Cultivated mushrooms sold for human consumption, such as button mushrooms (Agaricus bisporus) or shiitake, are considered safe for dogs. If you want to offer them occasionally, serve them cooked, in moderate amounts and always without garlic, onion, salt or sauces, which do disagree with them. Raw mushrooms are harder to digest. That said, mushrooms are not necessary in their diet: a balanced diet already covers their needs.

Wild mushrooms are another story: even if they are edible for you, like porcini, the wisest thing is never to give them to your dog.

acorns: an autumn walk classic

Holm oaks, oaks and cork oaks cover the paths with acorns in autumn. Dogs often nibble on them, but eating them in quantity is not a good idea. Why? Acorns are rich in tannins, substances that plants produce to defend themselves against the animals that eat them. They are responsible for the acorn’s rough, astringent taste, similar to the one a very strong tea leaves in your mouth.

The problem arises during digestion. Acorn tannins, known as hydrolysable tannins, break down into smaller compounds, such as pyrogallol, which pass into the blood and are eliminated through the kidney. This process has mainly been studied in cattle, where eating oak leaves and acorns has been linked to kidney damage and to symptoms such as diarrhoea, loss of appetite and weakness (Meiser et al., 2000; Plumlee et al., 1998). Few cases have been described in dogs, but they show a similar picture: vomiting, lethargy and changes in the liver and kidneys (Camacho et al., 2021; Jung et al., 2026).

In addition, whole or with its cup, an acorn can get stuck in the throat or intestine, especially in small dogs or those that swallow without chewing. If your dog has eaten several acorns, or you notice vomiting, loss of appetite or less urination than usual, talk to your vet.

chestnuts: not all of them are the same

In autumn it is also easy to find chestnuts on the ground, but it is worth knowing that two very different trees hide behind that name. The edible chestnut comes from the sweet chestnut tree (Castanea sativa), while the so-called horse chestnut comes from another tree, the horse chestnut (Aesculus hippocastanum), from a different genus (Pet Poison Helpline, n.d.-b). The edible chestnut is not considered toxic to dogs; its risk is mainly physical: whole or in its spiky husk, it can cause mouth injuries or get stuck in the intestine, and it is also hard for them to digest.

The horse chestnut, very common in parks and streets, is another story. Why? Its seeds and leaves contain triterpenoid saponins, such as aescin, and other compounds such as aesculin (ASPCA, n.d.; Pet Poison Helpline, n.d.-a). Saponins take their name from soap (sapo in Latin), because they foam in contact with water, just like soap. When they reach the stomach and intestine, they irritate the lining, which is why vomiting and diarrhoea are the most common signs. If the dog eats a larger amount, staggering or tremors may also appear (Pet Poison Helpline, n.d.-a). And if swallowed whole, the seed can cause an intestinal obstruction (Pet Poison Helpline, n.d.-b).

Telling them apart is easier than it seems. The husk of the sweet chestnut is covered in long, thin and very dense spines, and the chestnut itself is somewhat flattened and ends in a small point. The horse chestnut fruit, on the other hand, has a green shell with a few short, thick spikes, and its seed is round, very shiny and has a large pale patch.

conclusion: an autumn to enjoy together

Autumn is one of the best times to head out into the countryside with your dog, and there is no reason to give it up. Mushrooms, acorns and chestnuts are part of the landscape, but with a little attention on walks, some training and a quick call to the vet whenever in doubt, most scares come to nothing. Knowing the risks is not about living in fear, but about enjoying every walk with greater peace of mind.