My dog grazes: is he clearing himself out or worming himself?

It's a stubborn myth. The observations show that most grazing dogs are not ill beforehand , and grass has no worming effect at all. So there's no point adding fibre or supplementing "to make up for it": you don't supplement blindly.

Why my dog eats grass

Training & behaviourPart of · Training & behaviour

Why my dog eats grass

Q: Why does my dog eat grass?

Most often for the taste and the pleasure of exploring (it's foraging ), a behaviour inherited from wild canids. In a dog in good form, it's normal and nothing to worry about. Just stay alert to treated lawns and grass seeds in summer.

Q: Why does my dog eat grass and vomit?

Contrary to popular belief, he doesn't graze in order to vomit: in the studies, only around one dog in five vomits afterwards, and it's usually involuntary. That said, sudden, frantic grazing with retching can signal nausea, and a vet's opinion is worthwhile then.

Q: Is it dangerous for my dog to eat grass?

Grass itself, no. The risk comes from what's on it or around it: weedkiller, slug pellets, fertiliser , toxic plants mixed in with the lawn, and grass seeds in season. On an untreated lawn, calm grazing is digested without a hitch.

Q: What should I do if my dog eats grass and vomits often?

If the vomiting keeps recurring, or comes with low spirits, refusing food or blood, the grass is no longer the problem: ask your vet for advice. You can also limit access by working on a calm "leave it" on walks, without ever telling him off.

7 min read

A dog grazing on grass is almost always normal: not a sign of illness, not a “purge”, not a deficiency. Most dogs do it because they like the taste, and for the pleasure of nosing through the ground. What should catch your attention isn't how much he swallows, but the signs that come with it, or a treated lawn.

A behaviour inherited from his wild ancestors

Grazing is part of a dog's natural repertoire: it's most likely a behaviour inherited from his wild ancestors, who already nibbled on plants. Taste, texture and the urge to rummage through the ground explain most of it. You've done nothing wrong, and there's nothing to change about his bowl. When he grazes calmly and is otherwise doing fine, there's no need to interrupt him.

Grazing that's nothing to worry about

He grazes a little on the walk, then goes back to sniffing or playing.
He does it calmly, with no retching or drooling beforehand.
He's eating, drinking and in good form otherwise.
The lawn is neither treated nor full of grass seeds.

Grazing worth a closer look

He suddenly starts grazing frantically, as if “possessed”.
He retches or drools a lot before eating the grass.
He vomits several times after grazing, or stays off-colour afterwards.
He's also started swallowing soil or stones recently.
He's never done this before, and he's already an adult dog.

In a puppy or a young dog, it's even more ordinary: he explores everything with his mouth and tastes the world, grass included. The markers stay the same as for an adult: as long as he's doing fine, let him get on with it.

Grass itself isn't dangerous. The risk comes from what's on it or around it.

Genuinely worth avoiding

Treated lawn (weedkiller, fertiliser)He licks and swallows these products along with the grass. A recently treated lawn sometimes carries a small sign, or yellowed, discoloured patches. Be wary too of public spaces that have just been mown or treated. When in doubt, don't let him graze there.

Slug pellets (metaldehyde)They're highly toxic to dogs, with a risk of tremors and seizures. Never leave them within his reach.

Toxic plants mixed in with the grassA buttercup, an unearthed bulb, a berry fallen on the ground: while grazing, he doesn't sort through what he takes and can swallow them.

Worth keeping an eye on

Grass seeds (foxtails), in summerThese dry, dart-shaped seeds cling to the coat and can work their way into the skin, the nose or the ears. If he shakes his head non-stop, sneezes in bursts, licks at a paw or limps after a walk through dry grass, a grass seed may have lodged itself: head to the vet, and don't try to dig it out yourself.

Soil parasitesA dog grazing on soiled grass can pick up worms: worm him at the rhythm your vet advises.

Nothing to worry about

Grass from your own untreated lawnA bit of grass grazed calmly digests without any trouble.

It isn't the amount of grass that should worry you, but the signs that come with it. As long as he's fine otherwise, there's no such thing as “too much”. These few situations, though, are worth a call to your vet.

Keep an eye on it

He starts grazing all of a sudden, frantically, with retching or a lot of drool
He grazes when he never used to, and it comes with other changes (less appetite, less energy)

Time to see the vet

Repeated vomiting after he's grazed (several times in a row, not one isolated bout)
He refuses to eat, stays flat out and no longer comes to you, or diarrhoea sets in
He's also started eating soil or stones, a recent behaviour

Emergency

He may have grazed on a treated lawn (slug pellets, weedkiller) and starts trembling, staggering or having seizures
His belly is swollen and tight, with attempts to vomit but nothing coming up

Sueda et al. — Characterisation of plant eating in dogs (2008)
Hart B. L. — Why do dogs and cats eat grass?, Veterinary Medicine (2008)
Animal Poison Control Center (toxic plants and garden products), ASPCA

In the same family

guideWhy my dog eats poo (coprophagia)Another baffling but very ordinary eating behaviour, with the right reflexes to respond without stress, and to teach him to move on to something else.Read the guide guideWhy does my dog lick me?The same question asked of another very common gesture: why he does it, and whether you should worry about it.Read the guide guidePlants and flowers that are toxic to dogsIf he grazes in the garden or out on walks, it's worth knowing how to spot the plants that are toxic to him.Read the guide guideMy dog is vomiting or has diarrhoea: what to do, when to call the vetEnough to tell the difference between a harmless one-off bout of vomiting after grazing, and the signal that should take you to the vet.Read the guide guideExercising and occupying your dogA dog with plenty to do sometimes grazes less out of boredom: concrete ideas to spend his energy and his curiosity.Read the guide guideUnderstand before you judgeTo step back from behaviours that worry us for no good reason, and learn to read your dog before sounding the alarm.Read the guide

Frequently asked questions

Why does my dog eat grass?

Most often out of taste, and the pleasure of exploring: a behaviour most likely inherited from his wild ancestors. In a dog who is otherwise doing fine, it's normal and harmless. Do stay alert to treated lawns and to grass seeds in summer.

Why does my dog eat grass and vomit?

Contrary to popular belief, he isn't grazing to make himself sick: according to the large survey cited above, only about one dog in five regularly vomits afterwards, and it isn't deliberate on his part. Sudden, frantic grazing with retching, on the other hand, can signal nausea: a vet's opinion is worth having then.

Why does my dog eat grass every day?

Grazing a little each day, calmly, is part of his normal repertoire: for many dogs it becomes a small walking habit. It isn't the amount that matters, but how he's doing overall: as long as he's eating, drinking and playing as usual, it's nothing to worry about. Above all, check that the grass is neither treated nor full of grass seeds.

Is it dangerous for my dog to eat grass?

The grass itself, no. The risk comes from what's on it or around it: weedkiller, slug pellets, fertiliser, toxic plants mixed in with the lawn, and grass seeds in season. On an untreated lawn, calm grazing digests without any trouble.

My dog grazes: is he purging himself or worming himself?

It's a stubborn myth, but the figures contradict it: most dogs who graze are not often unwell beforehand. Nor does grass worm a dog: against worms, only a wormer given by your vet works. There's no need to add fibre to “make up for” a deficiency that has never been proven: ask your vet for advice instead.

What should I do if my dog eats grass and vomits often?

First look at whether it's genuine repeated vomiting (several times in a row, or with a dog who stays flat out, refuses to eat, or has blood in his vomit) or simply one isolated bout after grazing. If it keeps happening, the grass is no longer the problem: talk to your vet about it. To help him move on to something else rather than making a beeline for the grass on walks, you can teach him to turn away on a simple word: it's worked on calmly, like any real piece of learning, never by telling him off.

Updated on July 11, 2026Sources

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