Why Dogs Eat Grass — and Whether You Should Worry

Dogs Eating Grass

Grass-eating in dogs, sometimes called "pica" when it involves non-food items broadly, is a very common behavior where dogs deliberately chew and swallow grass. It happens in healthy dogs as well as those feeling unwell, and most veterinary experts consider it normal in the majority of cases. Despite widespread belief, research has not confirmed that dogs eat grass specifically to make themselves vomit.

A 2008 survey published in Applied Animal Behaviour Science found that grass was the most commonly eaten plant by dogs, and that illness before eating was rarely observed — challenging the self-medication hypothesis.

What the Research Actually Says

Walk through almost any neighborhood and you're likely to spot a dog pausing mid-walk to nibble the lawn. It's one of those behaviors owners notice constantly but rarely get a clear answer about. The most popular explanation — that dogs eat grass to settle an upset stomach or trigger vomiting — turns out to be largely a myth.

A widely referenced study published in Applied Animal Behaviour Science surveyed dog owners and found that most dogs showed no signs of illness before eating grass, and that vomiting after eating grass occurred in fewer than 25% of cases. That doesn't mean dogs never eat grass when they feel off — some might — but it's far from the rule.

This is one of several popular beliefs about dogs that science has largely disproven, where common wisdom and actual evidence point in different directions.

<25%

Dogs that vomit regularly after eating grass

A survey-based study in Applied Animal Behaviour Science found vomiting after grass consumption was the exception, not the rule.

~79%

Dog owners who report their dog eats plants

The same study found plant-eating — grass most commonly — to be a widespread behavior across dogs of all ages and diets.

~8%

Dogs appearing ill before eating grass

Only a small minority of dogs in the study showed signs of illness prior to eating grass, undermining the self-medication theory.

Why Dogs Eat Grass: The Leading Theories

Because no single cause has been confirmed, researchers and veterinarians generally discuss several overlapping possibilities:

Instinct and ancestry: Wild canids regularly consume plant matter — both directly and through the stomach contents of prey. Grass-eating may be a retained ancestral behavior with no strong modern purpose.
Fiber and digestion: Some animals seek out roughage to support gut motility. Dogs on lower-fiber diets may graze more, though this link hasn't been conclusively proven in controlled studies.
Boredom or sensory interest: Dogs that spend long stretches outdoors with limited stimulation may eat grass simply because it's there and mildly interesting. This relates to broader behavioral health — see our overview of what indoor vs. outdoor life means for a dog's health.
Taste preference: Some dogs appear to simply enjoy the texture or taste of certain grasses, particularly young, tender blades in spring.

Watch What's on the Grass, Not Just the Grass

The grass itself is rarely the danger — what's been sprayed on it is. Before allowing your dog to graze freely, confirm the area hasn't been treated with pesticides, herbicides, or synthetic fertilizers. When in doubt, redirect your dog and move on.

When to Actually Worry

For most dogs, eating a bit of grass on an untreated lawn is no more alarming than a child picking up a stick. The behavior becomes a concern in specific circumstances:

Sudden or compulsive increase: If a dog that rarely ate grass begins doing so obsessively, it warrants a veterinary evaluation. Compulsive behaviors can sometimes signal anxiety — similar patterns appear in dogs with separation anxiety.
Accompanying symptoms: Repeated vomiting, diarrhea, lethargy, loss of appetite, or visible abdominal discomfort alongside grass-eating should prompt a vet call.
Treated or unknown lawns: Pesticides, herbicides, and lawn fertilizers can be toxic to dogs. If you don't know whether a lawn has been chemically treated, keep your dog away from it.
Unknown plants nearby: Not all greenery is safe. Some ornamental grasses and common garden plants are toxic. If your yard includes plants you can't identify, review them against a veterinary toxicology resource.

If diet quality is a concern — for instance, if you're weighing an alternative feeding approach — it's worth reading about the case for and against raw feeding before making any changes.

Grass-Eating in Puppies vs. Adult Dogs

Puppies explore the world through their mouths and may eat grass simply out of curiosity — this tends to taper off with age. Adult dogs that suddenly begin eating grass in large quantities after years of not doing so deserve more attention, as the change in behavior itself is the signal worth investigating.

What You Can Do

If your dog eats grass occasionally with no other symptoms, the honest answer is: you probably don't need to do anything. That said, a few practical steps can reduce any associated risk:

Keep your own lawn free of chemical treatments, or create a designated untreated area where your dog can safely graze.
If you suspect boredom is a factor, increase daily enrichment — more walks, puzzle feeders, or play sessions.
Discuss any dietary concerns with your veterinarian rather than making significant food changes independently. Good overall nutrition — including oral health, since dental disease is one of the most preventable conditions in dogs — supports general well-being.
Know what plants grow in spaces where your dog roams. The ASPCA's Animal Poison Control Center maintains a publicly available toxic plant list.

This article is for general informational purposes only and is not a substitute for veterinary advice. If your dog shows signs of illness, contact a licensed veterinarian.

Frequently Asked Questions

Is it normal for dogs to eat grass every day?

Frequent grass-eating is common in many dogs and is usually not cause for alarm. However, if the behavior is new, sudden, or has dramatically increased, it's worth a vet visit to rule out digestive issues or nutritional gaps.

Does eating grass mean my dog is sick?

Not necessarily. Studies show the majority of dogs that eat grass show no signs of illness beforehand. That said, if your dog seems lethargic, is vomiting repeatedly, or stops eating regular food, contact your veterinarian.

Should I stop my dog from eating grass?

Occasional grass-eating on untreated lawn is generally fine. The main concern is grass that has been treated with pesticides, herbicides, or fertilizers, which can be toxic. Keep your dog away from chemically treated areas.

Do dogs eat grass because they lack fiber?

This is one proposed explanation — that dogs seek fiber to aid digestion — but it hasn't been definitively proven. If you suspect a dietary issue, speak with your vet before making changes to your dog's food.

Will grass make my dog vomit?

It might, but it's not a given. Research suggests fewer than 25% of dogs vomit regularly after eating grass. Most dogs appear to eat and digest it without obvious ill effects.

Are any grasses or plants dangerous for dogs?

Yes — certain ornamental grasses and many common lawn and garden plants are toxic to dogs. The ASPCA maintains an updated list of toxic and non-toxic plants at their website. If you're unsure what grows in your yard, review it before letting your dog graze.

Pets & Animals Editorial Team · Contributor

Pets & Animals Editorial Team is the collective byline for our editorial team and contributor network. Articles published under this byline or an editorial pen name are researched, written, and reviewed according to our editorial standards for clarity, consistency, and independence before publication.

The content on this site is for informational purposes only and is not a substitute for professional advice. Always consult a qualified professional for guidance specific to your situation.