Question
Why does my dog eat grass?
The short answer
Grass eating is common and usually normal. In a large owner survey, most dogs ate plants regularly, few seemed ill beforehand and only about one in five often vomited afterwards. Nobody knows the exact reason: it may be an inherited habit from wild ancestors, or dogs may simply like it. Keep your dog off sprayed lawns and toxic plants, and see a vet if it vomits often, seems unwell or suddenly eats grass frantically. Kroki, a reward-based training app for puppies and dogs, teaches Leave it in short steps.
How to do it, step by step
Let a healthy dog nibble in safe places
If your dog is otherwise bright, eats normally and only vomits now and then, an occasional mouthful of grass is not a problem in itself. You do not need to stop it altogether. Focus on where it happens rather than on whether it happens.
Avoid treated grass and toxic plants
Lawns, verges and fields may be sprayed with weed killers, pesticides or fertiliser, and slug pellets are sometimes scattered in gardens. Know which plants in your own garden are toxic to dogs, and steer your dog away from unknown green areas.
Watch out for grass seeds in summer
Long, dry grass with arrow-shaped seed heads can get stuck in paws, ears, noses and eyes. Keep your dog to short grass in late summer and check its coat, paws and ears after walks.
Teach Leave it for the places you want to skip
Practise Leave it at home first: when your dog looks away from a treat in your closed hand, say “Top!” and reward from the other hand. On walks, use it where the grass may be treated, and reward your dog with something better than grass.
Offer other ways to explore
Some dogs graze more when walks are short or boring. Let your dog sniff at its own pace, scatter a few treats in a safe patch of grass, and reward it when it checks in with you on its own.
Keep a simple note when something changes
If grass eating suddenly increases, write down how much, when, and whether your dog vomits, has diarrhoea, eats less or seems flat. These notes help your vet decide whether to look for a health cause.
Puppy or grown dog?
Young dogs tend to eat plants more often than older ones, and in the big survey they were less likely to seem ill before or vomit afterwards. With a puppy the main risk is that it mouths everything, so teach swapping and Leave it early and keep it away from toxic plants. In an older dog, a sudden change in grass eating, especially with vomiting or tiredness, deserves a vet check.
What science knows, and what it does not
The best-known study is an owner survey from the University of California, Davis. Of 3,340 returned questionnaires, 1,571 met the criteria. In that group, 68 percent of dogs ate plants daily or weekly, and grass was the plant most often eaten. Only 9 percent of owners said their dog frequently seemed ill before eating plants, and 22 percent said it frequently vomited afterwards (Sueda and colleagues 2008). So the common idea that dogs eat grass to make themselves sick does not fit most dogs.
The survey found no link between plant eating and sex, neutering, breed group or the type of diet. Younger dogs ate plants more often and were less likely to seem ill or vomit around it. The authors concluded that plant eating is a normal behaviour of domestic dogs (Sueda and colleagues 2008).
Why dogs do it is still unclear. The lead researcher’s working idea is that it is an inherited habit: plant material turns up in the droppings and stomach contents of wild canids, and eating plants may once have helped push intestinal worms through the gut (Hart 2008). This is a hypothesis, not a proven fact, and the same summary reports that dogs on lower-fibre diets did not eat more plants. Simply liking the taste or texture of fresh grass is another explanation nobody has ruled out.
Common myths about grass eating
- “Dogs eat grass to make themselves sick.” Most dogs in the survey did not seem ill before and did not vomit afterwards.
- “It means something is missing from the diet.” The survey found no link with diet type, and lower-fibre diets did not go with more plant eating.
- “Grass eating is always harmless.” The behaviour is normal, but sprayed grass, toxic plants and grass seeds are real risks.
- “You must stop it at all costs.” In a healthy dog, managing where it grazes matters more than banning it.
When to see a professional
Grass eating is usually normal. Get help if:
your dog has eaten plants or grass that may be toxic or treated with chemicals or slug pellets, or it drools, trembles, staggers or collapses
Emergency: get help nowyour dog vomits often, has diarrhoea or blood in vomit or stool, is lethargic, eats less, loses weight, or suddenly eats grass frantically
Have a vet take a lookyour dog sneezes, shakes its head, paws at an ear or eye, or licks one paw a lot after walking through long grass
Have a vet take a look
The help pages list services in Germany, Austria and Switzerland only. Elsewhere, ask your vet practice who they recommend near you.
Frequently asked questions
Should I worry if my dog eats grass and then throws up?
Not usually, if it happens now and then and your dog is otherwise well. If it vomits often, seems unwell, or you see blood, ask your vet.
Why does my dog eat grass every time we go outside?
Many healthy dogs graze on almost every walk, and young dogs do it most. Check that the grass is untreated, keep walks varied with plenty of sniffing, and see a vet if it is a new habit.
Does eating grass mean my dog has an upset stomach?
Most of the time, no: in a large survey only a small share of dogs seemed ill before eating plants. A dog that suddenly eats grass urgently while seeming uncomfortable is different and should see a vet.
Can grass be dangerous for my dog?
Grass itself is rarely the problem, but chemicals, slug pellets, toxic garden plants and sharp grass seeds can be. Choose untreated areas and check paws, ears and nose after summer walks.
Should I change my dog’s food if it eats grass?
Not because of grass eating alone. The survey found no link with diet type or fibre. If you have other concerns about its food or weight, discuss them with your vet.
Is it fine to let my puppy eat grass?
A few mouthfuls of untreated grass are fine for most puppies. Puppies tend to graze more than adult dogs, so keep them away from toxic plants and practise swapping and Leave it early.
Can I stop my dog eating grass on walks?
Yes, with Leave it and a better reward for looking at you instead. Use it where grass may be treated, and let your dog graze safely elsewhere if it is healthy.