Last reviewed October 2026. This guide is educational and is not veterinary advice. If you are worried about your dog, call your vet.
Quick answer
Eating grass is common and usually normal for dogs. Researchers have not found one single cause, and most grass-eating dogs are not sick beforehand and do not vomit afterward. The real risks come from what is on the grass (lawn chemicals and parasites) and from patterns that signal illness, such as repeated vomiting, lethargy, or compulsive eating of non-food items. Those are the times to call your vet.
Watching your dog chew mouthfuls of lawn is confusing, especially when the popular explanation is “he has an upset stomach.” The research tells a more nuanced story, and knowing it helps you tell harmless grazing from a problem worth acting on.
In this guide
How common is grass eating?
Very common. In a 2008 report on research by Dr. Benjamin Hart at UC Davis, published by dvm360, 68% of owners surveyed said their dogs ate plants daily or weekly. Only 8% said their dogs frequently showed signs of illness before eating plants, and 22% said their dogs regularly vomited afterward. In a smaller survey of 25 veterinary students who owned dogs, every dog ate grass, none showed signs of sickness first, and only 8% regularly vomited afterward.
The researcher’s conclusion was that grass eating is a common behavior in normal dogs and is not generally tied to illness. The same report noted one useful exception: dogs that did look unwell before eating plants were more likely to vomit afterward.
Why dogs eat grass: theories vs. evidence
| Theory | What the evidence suggests | Status |
|---|---|---|
| “He’s sick and wants to vomit” | Most dogs show no illness beforehand and most do not vomit afterward (see the figures above). | Weak support |
| Soothing stomach acid | Suggested by AKC’s chief veterinary officer as a possible reason some dogs eat grass to release bile, but it is a theory, not a proven cause. | Possible, unproven |
| Missing nutrients | The 2008 study author described grass as having no apparent nutritional value, though some scientists have suggested micronutrients such as B vitamins, as reported by Live Science. | Possible, unproven |
| Ancestral instinct (clearing parasites) | Scientists have hypothesized that wild canines eat grass to clear their intestines of parasites. Domestic dogs may keep the habit. | Hypothesis |
| Taste, texture or boredom | Many vets simply say some dogs like it. Veterinarians quoted by Live Science say there is no one reason. | Plausible |
Our takeaway: treat grass eating as a normal, mostly harmless habit by default, and judge each dog by the pattern around it rather than by the grass alone. Sources for this section: the American Kennel Club and Live Science.
The real risks: chemicals, parasites and toxic plants
For most dogs the grass itself is not the problem. What is on or in it can be:
- Lawn chemicals. The AKC warns that grass treated with herbicides and pesticides can be toxic to dogs. Keep dogs off recently treated lawns and follow the product label’s instructions on waiting times.
- Parasites. Grass contaminated by animal droppings can carry intestinal parasites such as roundworms and hookworms. Regular deworming and picking up waste lowers the risk; see our flea and tick prevention guide for year-round parasite protection.
- Other plants. Dogs that graze may also nibble garden plants, and some are toxic. If you are unsure what your dog ate, call your vet or an animal poison hotline.
When to call your vet
| What you see | What to do |
|---|---|
| OK: occasional grazing, bright and eating normally | Usually nothing. Make sure the lawn is untreated and clean. |
| Watch: one vomit after grass, then back to normal | Monitor. See our guide to dog vomiting. |
| Watch: sudden increase in grazing, or eating grass frantically | Book a vet visit if it continues for days or comes with diarrhea (dog diarrhea guide). |
| Watch: also eating dirt, rocks, fabric or other non-food items | The AKC notes extreme habits may be pica. Ask your vet. |
| Urgent: repeated vomiting, lethargy, loss of appetite, blood in vomit or stool, or possible chemical or plant exposure | Call your vet or an emergency clinic today. See also signs your dog may be unwell. |
How to reduce grass eating
You do not have to stop a harmless habit, but you may want to limit it, especially on lawns you cannot vouch for. Try these in order:
- Make the lawn safe first. Stop or switch lawn treatments, or keep your dog off treated areas until the product label says it is safe.
- Rule out a medical cause. If grazing has changed suddenly or comes with vomiting, diarrhea or appetite changes, let your vet check before you try to train it away.
- Add exercise and enrichment. Boredom is a commonly suggested reason, so extra activity cannot hurt. See how much exercise a dog needs and indoor activities for dogs.
- Redirect, don’t punish. As the AKC suggests, offer a more exciting toy or treat when your dog starts to graze, and reward your dog for coming away. Our recall training plan helps here.
- Use a leash on unfamiliar ground. Parks and sidewalks are the likeliest places for chemicals and droppings.
FAQ
Is it normal for dogs to eat grass every day?
It can be. In the UC Davis survey, a majority of owners reported daily or weekly plant eating without signs of illness. Daily grazing alone is not a red flag; vomiting, low energy or appetite changes alongside it are.
Why does my dog eat grass and then throw up?
Some dogs do vomit afterward, particularly on an empty stomach, but most do not. If it happens often, mention it to your vet instead of assuming it is routine.
Do puppies eat more grass than adult dogs?
Puppies explore with their mouths, so grass, sticks and leaves all get tasted. Watch young dogs closely for anything swallowed, and see our puppy teething guide for chewing behavior.
Does eating grass mean my dog has worms?
Not necessarily. The idea that dogs eat grass to clear parasites is a hypothesis, not a diagnosis. Grass can however expose dogs to worms, so keep up with your vet’s deworming advice.
Should I stop my dog from eating grass completely?
Not unless the grass may be treated, contaminated or comes with symptoms. For a healthy dog on a clean lawn, occasional grazing is generally considered normal.
The bottom line
Grass eating is one of the most common dog habits, and the research does not support the old idea that it always means an upset stomach. Keep your dog away from treated or dirty grass, watch for vomiting, lethargy or non-food eating, and talk to your vet if the pattern changes.
Sources and further reading
- dvm360: CVC 2008 highlights, why do dogs and cats eat grass?
- American Kennel Club: Why does my dog eat grass?
- Live Science: Why do cats and dogs eat grass?
Photo: Henrik L. on Unsplash (Unsplash License). This article is general information, not veterinary advice.