Why Do Dogs Eat Grass?
Every dog owner has watched it: the walk stops, the dog finds a particular patch of grass, and he eats it with real concentration. Sometimes he brings it back up ten minutes later.
The usual explanation is that he's ill and eating grass to make himself sick. The research mostly says otherwise.
How common is it?
Very. A survey of 1,571 dog owners found 68% of dogs ate plants daily or weekly, and grass was by far the most common plant, eaten by 79% of them (Applied Animal Behaviour Science, 2008).
The same survey asked about illness. Only 9% of dogs were reported to often look unwell before eating plants. Only 22% often vomited afterwards. The authors' conclusion was that plant eating is a normal behaviour in dogs, not a sign of sickness.
So the dog who chews grass and then trots on is the typical case. The one who eats it and vomits is the minority.
Do dogs eat grass to settle an upset stomach?
Someone tested it. Researchers fed a group of dogs their normal diet, then the same diet with an added fibre (fructo-oligosaccharide, or FOS) that gave them temporarily loose stools, and recorded how much grass they ate when it was offered (Applied Animal Behaviour Science, 2010).
If dogs ate grass to treat a bad stomach, they should have eaten more while their stools were loose. They ate less. Grass eating was higher on the normal diet, with normal stools.
Vomiting was rare, too: two vomits in 374 recorded bouts of grass eating. Grass was not working as an emetic.
The authors were careful about what this does and doesn't rule out. Loose stool is one kind of gut discomfort; nausea or constipation might be different, and nobody has tested those properly.
Could it be about fibre?
Possibly, and this is the part people tend to overstate, so here it is plainly.
In that same study, the dogs ate less grass during the fibre phase, and the authors suggested the fermenting fibre might have left them feeling fuller. There's also a single case report: a miniature poodle who had eaten plants and vomited daily for seven years stopped within three days of moving to a high-fibre diet, and hadn't restarted 13 months later (Journal of Veterinary Medical Science, 2007).
Twelve dogs in one study, one dog in another. That's a hint, not an answer. It is not evidence that adding fibre will stop your dog eating grass, and it's certainly not evidence that any particular chew will, ours included.
The parts of grass eating that are actually risky
Grass itself isn't the danger. What's on it, or growing next to it, can be.
Sprays. Lawns, parks and society gardens get treated with pesticides and fertilisers. A dog grazing a freshly treated patch is eating whatever was sprayed on it. Stick to grass you know about.
Oleander. Very common across India on road dividers, in gardens and outside housing societies. Every part of the plant is toxic to dogs; it contains compounds that act on the heart, and the signs include drooling, abdominal pain, diarrhoea and, in serious cases, death (ASPCA). A dog who chews leaves indiscriminately on a walk is at risk from it. If you think he's eaten oleander, go to a vet immediately.
Other dogs' leftovers. Grass on a busy walking route isn't just grass, and a dog nosing through it often finds something worse; we've covered [why dogs eat poop](/blogs/news/why-do-dogs-eat-poop) separately.
When grass eating is worth a vet visit
Most of the time it isn't. A few patterns are different.
A sudden change: a dog who rarely grazes and now does it frantically. Grass eating alongside repeated vomiting, diarrhoea, weight loss or a dog who seems unwell in himself. Daily vomiting after grazing that's been going on for weeks. Any of those is a reason to get the dog checked rather than put it down to habit.
Our [when to see a vet](/blogs/news/when-to-take-dog-to-vet-digestive-problems) guide lists the signs that mean go now.
What to do about a dog who grazes
If he's healthy and the grass is clean, you don't need to stop it. Plenty of dogs do it their whole lives.
If you'd rather he didn't, the practical tools are dull ones: walk him on a lead past the patches he favours, teach a solid "leave it", and keep him off grass you know has been sprayed. Make sure his normal diet is complete and that he's actually getting enough to eat. A small Australian study found dogs spent more time grazing before their meal than after it, and were less likely to graze when full (Bjone et al., University of New England, 2007); a walk just after breakfast may simply involve less grass.
Where ChewCheer fits
Carefully. Our working ingredients, chicory root fibre and inulin, belong to the same family of fermentable fibre as the FOS used in that study. That's interesting. It is not a reason to think the chew changes grass eating, and we don't claim it does. Dog studies on this fibre have measured stool quality, not grazing.
The short version
Most dogs eat grass, most of them aren't ill when they do it, and most don't vomit afterwards. The one controlled test found dogs didn't eat more grass when their stomachs were upset. Watch for sprayed lawns and oleander, and see a vet if grazing suddenly changes or comes with other signs.
Frequently asked questions
Why do dogs eat grass?
Mostly because it is normal dog behaviour. In a survey of 1,571 owners, 68% of dogs ate plants daily or weekly and grass was the most common. Only 9% often looked ill beforehand and only 22% often vomited afterwards. The idea that dogs eat grass mainly because they feel sick isn't well supported.
Do dogs eat grass to make themselves vomit?
Usually not. In a controlled study, vomiting followed just 2 of 374 bouts of grass eating. Dogs also ate less grass, not more, when a dietary fibre gave them loose stools. That suggests grass isn't used to treat diarrhoea, though nausea and constipation haven't been properly tested.
Should I stop my dog eating grass?
Not if he's healthy and the grass is clean. The real risks are lawns treated with pesticides or fertiliser and toxic plants nearby, especially oleander, which is common in India. Keep him off sprayed areas, teach a 'leave it', and walk on a lead past plants you can't identify.
Does a lack of fibre make dogs eat grass?
It might in some dogs, but the evidence is thin: one study of twelve dogs saw less grass eating while they were fed added fibre, and one case report described a poodle who stopped after a high-fibre diet. That is a hint rather than proof, and it doesn't show any particular product will change grazing.
Is oleander dangerous to dogs?
Yes. All parts of the oleander plant are toxic to dogs. It contains compounds that act on the heart, and signs include drooling, abdominal pain, diarrhoea and, in severe cases, death. It grows widely on Indian roadsides and in gardens. If you suspect your dog has eaten any, go to a vet immediately.
When is grass eating a sign of illness?
When it changes suddenly, becomes frantic, or comes with repeated vomiting, diarrhoea, weight loss or a dog who seems unwell. Daily vomiting after grazing that has gone on for weeks is also worth a vet check rather than assuming it is habit.