Why Does My Dog Eat Grass? 5 Real Reasons (and When to Worry)
Shiloh’s House Team
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5 min read
Your dog eats grass because dogs eat grass. In the largest study on the subject (1,571 dogs, UC Davis School of Veterinary Medicine), 68% of dogs ate grass or other plants weekly or daily, only 8% looked sick beforehand, and only 22% vomited afterward. Diet made no difference. The researchers concluded that plant eating is a normal behavior inherited from wild ancestors, not a sign of illness, nausea or a missing nutrient. It becomes a problem only if your dog seems unwell before eating it, vomits repeatedly, eats it frantically, or grazes on a treated lawn.
Why do dogs eat grass? What the research says
Veterinary behaviorist Benjamin Hart and colleagues at UC Davis surveyed dog owners in two studies published in 2008 in Applied Animal Behaviour Science. Among 1,571 usable responses, 79% of plant-eating dogs chose grass most often, younger dogs ate plants more frequently than older dogs, and dogs on commercial, raw or home-cooked diets all grazed at about the same rate. The authors’ working theory: wild canids eat plant material to help purge intestinal parasites, and domestic dogs kept the habit. Plant material shows up in anywhere from 2% to 74% of wild wolf and cougar scat samples.
The 5 real reasons dogs eat grass
1. It’s instinct
The best-supported explanation. Grazing is common in healthy dogs of every breed and age, and it doesn’t correlate with diet or illness. Puppies and young dogs do it most.
2. They like it
Fresh spring grass is sweet and crunchy. Many dogs graze selectively, picking certain blades and ignoring others, which looks a lot more like snacking than self-medicating.
3. Boredom or habit
Dogs left in a yard with nothing to do will investigate what’s there. If grazing increases when your dog is under-exercised or alone, more walks and enrichment usually reduce it. (The same goes for the stranger habits in our guide to why dogs eat poop.)
4. Fiber
Grass is roughage. The UC Davis data didn’t find a link between low-fiber diets and more grazing, so this is a weaker explanation than the internet suggests, but adding a little fiber (plain canned pumpkin, green beans) is a harmless thing to try if your dog grazes a lot.
5. An upset stomach (less often than you’d think)
Only about 8% of dogs in the study appeared ill before eating grass, and the dogs that did were more likely to vomit afterward. So for a minority of dogs, grazing may be a response to nausea. If your dog is one of them, the grass isn’t the issue; whatever is causing the nausea is. Our guide to why dogs throw up covers the causes worth a call to the vet.
Does eating grass make dogs throw up?
Sometimes, but it’s usually incidental. In the UC Davis study, 78% of dogs rarely or never vomited after eating plants. Hart’s interpretation: vomiting is a side effect of the grass, not the purpose of eating it. One odd finding the authors couldn’t explain is that dogs on commercial diets were more likely to vomit after grazing than dogs fed raw or home-cooked food.
When grass-eating means a vet visit
Call your vet if your dog seems unwell before grazing (lethargy, drooling, lip-licking, restlessness), vomits more than once or twice after it, suddenly starts grazing frantically when he never did before, or has diarrhea, weight loss or a poor appetite alongside it. Those patterns point to a GI problem that needs a workup, not a lawn problem.
When the grass itself is the danger
The grass is harmless. What’s on it may not be. Keep grazing dogs off lawns treated with herbicides, pesticides or fertilizer until the product’s label says it’s safe, and off any area where rodenticide or snail bait has been used. Also watch for the plants growing in and around the grass: many common yard and garden plants are toxic to dogs, and fall brings its own list, which we covered in are mums toxic to dogs?. Because grazing is tied to the parasite-purging instinct, it’s also a good reminder to keep your dog on a year-round dewormer and monthly parasite preventive.
How to stop a dog from eating grass
You mostly don’t need to. If you want to reduce it: add exercise and enrichment, teach a solid “leave it,” walk on a shorter leash past tempting patches, and try adding a tablespoon of plain pumpkin or a few green beans to meals for fiber. Don’t punish it; it’s normal, and punishment just makes dogs sneaky grazers.
One more thing about dogs with their nose in the grass: a dog that wanders the yard grazing is a dog near the fence line. A Shiloh’s House smart tag means the neighbor who finds him can tap it with their phone and call you in seconds.
Not tagged yet?
Tap-to-find smart ID tags. $38, one-time, no battery, no subscription, made in the USA. Free Lohji app included.
Frequently asked questions
Is it OK for dogs to eat grass?
Yes, for most dogs. The largest study on the behavior found 68% of dogs eat grass regularly and it isn’t linked to illness or diet. Just keep them off chemically treated lawns.
Do dogs eat grass when their stomach hurts?
Rarely. Only about 8% of dogs in the UC Davis study appeared ill before eating grass, and only 22% vomited afterward. For most dogs, grazing is instinct, not nausea.
Why does my dog eat grass and then throw up?
Occasional vomiting after grass is normal and incidental. If it happens repeatedly, or your dog seems sick before eating grass, see your vet; the cause is likely a GI issue, not the grass.
Are dogs missing something in their diet if they eat grass?
Probably not. Researchers found no link between diet type or fiber level and how often dogs eat grass. Adding a little fiber is harmless but unlikely to stop it.
How do I stop my dog from eating grass?
More exercise and enrichment, a reliable “leave it,” a shorter leash near tempting patches, and a little added fiber. Don’t punish it.
Sources
- Sueda, K.L.C., Hart, B.L. & Cliff, K.D. (2008). “Characterisation of plant eating in dogs.” Applied Animal Behaviour Science, 111, 120–132.
- Hart, B.L. (dvm360), “Why do dogs and cats eat grass?” — summary of the UC Davis findings and the parasite-purging hypothesis.
