Dogs eat grass because it’s a normal part of canine behavior, not because something is wrong with them. A 2008 study from the University of California, Davis surveyed 1,571 dog owners and found that 68% of dogs eat plants regularly, with grass being the most common choice. Only 22% of those dogs vomited afterward, and just 9% appeared sick beforehand. The “dogs eat grass to throw up” idea? Mostly a myth.
In Short: Grass eating is normal dog behavior rooted in dietary instinct. Research shows most dogs do it, most don’t vomit after, and most aren’t sick when they do it. The only time to worry is if your dog is eating grass obsessively, refusing food, or if the lawn has been treated with pesticides or herbicides.
Still, I get the concern. Winston goes through phases where he grazes like a small, curly cow, and the first time he did it I was convinced he’d swallowed something toxic. He hadn’t. He was just being a dog.
Here are the real reasons your dog eats grass, backed by actual research, not just guessing.
1. It’s an Instinct They Never Lost
Dogs are omnivores, not strict carnivores. Their wolf ancestors ate the stomach contents of herbivore prey, which included partially digested plant matter. A study published in the Journal of Veterinary Behavior (Sueda et al., 2008) confirmed that plant eating in domestic dogs appears to be a retained ancestral behavior rather than a response to illness or dietary deficiency.
Wild canids, wolves, coyotes, foxes, still eat grass and berries regularly. Your dog doesn’t know they live in a house with a memory foam bed. Part of their brain still thinks they’re foraging.
This is probably the single biggest reason most dogs eat grass. It feels right to them. Not every behavior needs a medical explanation.
2. They Want More Fiber
Grass is mostly insoluble fiber, and some dogs seek it out when their diet is low in roughage. A case report published in the Journal of Veterinary Medical Science described a Miniature Poodle that ate grass and plants daily for seven years. When the owner switched to a high-fiber diet, the grass eating stopped within three days.
One case report isn’t definitive proof. But it lines up with what veterinary nutritionists say: dogs on low-fiber kibble sometimes self-supplement by eating grass.
If your dog eats grass frequently, look at their food’s crude fiber content. Most dry dog foods contain 3-5% fiber. Dogs who eat grass regularly may do better with a food that’s closer to 6-8%, or with the addition of a fiber source like plain canned pumpkin (not pumpkin pie filling, big difference). A tablespoon or two mixed into their meal often does the trick.
3. They Like How It Tastes
This one is less scientific and more observational, but talk to enough dog owners and a pattern emerges: dogs tend to eat young, fresh grass, the new growth, not the old dry stuff. Veterinary behaviorist Dr. Benjamin Hart at UC Davis has noted that dogs appear to be selective about which grass they eat, suggesting taste and texture play a role.
Some dogs go for specific patches in the yard and ignore others. Some only eat grass after rain, when it’s wet and tender. This isn’t a dog in distress looking for medicine. It’s a dog who found something they like to chew on.
4. They’re Bored
A dog left in the backyard with nothing to do will find something to do. Sometimes that something is grass. Understimulated dogs, especially high-energy breeds like Australian Shepherds, Border Collies, and Labrador Retrievers, are more likely to develop repetitive behaviors including excessive grass eating.
If your dog eats grass mainly when they’re alone in the yard, boredom is a strong possibility. More exercise, puzzle feeders, or just spending time outside with them usually reduces the behavior. Not because grass eating is dangerous, but because a mentally engaged dog has better things to do.
5. Their Stomach Is Upset (Sometimes)
Here’s where the old wives’ tale has a grain of truth. Some dogs do eat grass when they feel nauseous, and some do vomit afterward. The UC Davis study found that dogs described as appearing “sick” before eating grass were four times more likely to vomit afterward compared to dogs who seemed normal.
But the key word is “some.” The majority of grass-eating dogs aren’t sick. The study’s lead author, Dr. Karen Sueda, concluded that the data “does not support the notion that grass eating is a common cause of vomiting, or that dogs commonly use grass as a self-medication strategy.”
So if your dog eats grass occasionally and doesn’t vomit, no issue. If they suddenly start eating grass frantically, retching, and refusing their regular meals, that’s a different situation entirely. That warrants a vet call, not because of the grass but because of the sudden change in behavior.
6. Pica or Compulsive Behavior
Pica is the clinical term for eating non-food items. In dogs, it can include grass, dirt, rocks, socks, and basically anything that isn’t food. When grass eating becomes obsessive, your dog can’t stop, does it for extended periods, or eats large quantities, pica might be the explanation.
Pica in dogs can be triggered by:
- Nutritional deficiencies (especially iron or zinc)
- Gastrointestinal disorders
- Anxiety or stress
- Certain medications
A study in the Journal of Applied Animal Behaviour Science found that dogs with separation anxiety were significantly more likely to engage in pica behaviors. If the grass eating happens primarily when you’re away or during stressful events (thunderstorms, fireworks, new environments), anxiety could be the driver.
Your vet can run bloodwork to rule out nutritional deficiencies and recommend a behavioral assessment if they suspect anxiety is involved.
7. There’s Something in the Grass
This one isn’t about why they eat grass, it’s about what might be ON the grass. If your dog is eating grass near spots where other animals frequent, they may be attracted to scent traces from rabbit droppings, bird waste, or other animal residue. Dogs have 300 million olfactory receptors compared to our 6 million. They’re picking up things we can’t even imagine.
This is worth thinking about because the grass itself isn’t usually the problem. What’s on the grass can be.
When Grass Eating Is Actually a Problem
Most grass eating is harmless. But there are a few situations where you should pay attention.
Pesticides and Herbicides
This is the real danger. The grass itself won’t hurt your dog. The chemicals sprayed on it absolutely can. A 2013 study published in Science of the Total Environment found that lawn chemicals were detected in the urine of dogs from 19 of 25 households tested, including households that didn’t treat their own lawns. Drift from neighboring properties was enough.
Common lawn chemicals like 2,4-D (the most widely used herbicide in North America) have been associated with increased risk of canine malignant lymphoma in multiple studies, including a 2012 paper from Tufts University’s Cummings School of Veterinary Medicine.
If your dog eats grass, make sure you know what’s on it. Keep them off freshly treated lawns, yours and your neighbors’. Look for the small warning signs that lawn care companies leave behind.
Sudden Obsessive Grass Eating
If a dog who doesn’t normally eat grass suddenly starts doing it compulsively, gulping down large quantities, eating it frantically, that can signal gastrointestinal distress. Conditions like inflammatory bowel disease, gastric ulcers, or even an intestinal blockage can trigger this behavior.
Pair it with other symptoms, loss of appetite, lethargy, diarrhea, repeated vomiting, and you’ve got a vet visit. Don’t wait on this one.
Parasites
Grass itself doesn’t contain intestinal parasites, but contaminated soil and feces in grassy areas can. Dogs who graze in parks, dog runs, or shared green spaces have higher exposure to hookworms, roundworms, and giardia. Keep up with your dog’s regular deworming schedule, and consider fecal testing annually if your dog is a habitual grass eater.
What You Can Do About It
Honestly? In most cases, nothing. If your dog eats grass occasionally, doesn’t vomit, and seems perfectly fine otherwise, leave it alone. It’s normal.
But if you want to reduce the behavior:
- Check your dog’s fiber intake. Switch to a food with higher crude fiber or add a tablespoon of plain canned pumpkin to meals. Our dry dog food guide covers several options with good fiber content.
- Provide more enrichment. A bored dog in a yard full of grass is going to eat the grass. Puzzle toys, snuffle mats, and more structured exercise help.
- Make sure the grass is safe. No pesticides, no herbicides, no fertilizer. If you can’t confirm what’s on the lawn, redirect your dog to a different area.
- Talk to your vet if it’s new or excessive. A sudden change in behavior always warrants a check-in. Bloodwork can rule out deficiencies, and your vet can assess for GI issues.
FAQ
Is it safe for dogs to eat grass every day?
For most dogs, eating grass daily is not harmful and falls within the range of normal canine behavior. The UC Davis study of 1,571 dog owners found that the majority of dogs who ate plants regularly showed no signs of illness before or after eating grass. The main safety concern isn’t the grass itself but what might be on it, pesticides, herbicides, and fertilizers pose the real risk. As long as the grass is untreated, daily grazing is rarely a problem worth losing sleep over.
Do dogs eat grass to make themselves throw up?
The popular belief that dogs eat grass to induce vomiting isn’t well supported by research. Only about 22% of dogs vomit after eating grass, according to the UC Davis study, and fewer than 10% appeared unwell before eating it. Some dogs with nausea do eat grass and then vomit, but the majority eat grass without any stomach issues at all. If your dog is vomiting frequently after eating grass, it’s worth a vet visit, but the grass probably isn’t the cause.
Should I stop my dog from eating grass?
You don’t need to stop your dog from eating grass unless the lawn has been treated with chemicals, your dog is eating grass obsessively (large quantities, frantic behavior), or the grass eating accompanies other concerning symptoms like vomiting, diarrhea, or refusing food. Occasional grass eating is a normal instinct. Trying to suppress every natural behavior can cause more stress than it prevents. Focus on making sure the grass is clean and your dog’s diet has adequate fiber.
Can grass eating be a sign of a serious illness?
Occasional grass eating is almost never a sign of serious illness. But a sudden onset of frantic, compulsive grass eating, especially if paired with vomiting, weight loss, or appetite changes, can indicate gastrointestinal problems like inflammatory bowel disease, gastric ulcers, or intestinal parasites. Nutritional deficiencies, particularly in iron or zinc, can also drive pica behaviors that include excessive plant eating. If the behavior is new, intense, or accompanied by other symptoms, bloodwork and a veterinary exam can rule out underlying conditions.
Does eating grass mean my dog’s food isn’t good enough?
Not necessarily. Most dogs who eat grass are on perfectly adequate diets. But dogs on low-fiber kibble (under 3% crude fiber) are more likely to seek out plant material as a supplement. If your dog eats grass frequently, checking the fiber content of their food is a reasonable first step. Adding plain canned pumpkin or switching to a higher-fiber kibble has been shown to reduce grass eating in some dogs. But plenty of dogs on premium food still munch on grass, because it’s an instinct, not always a deficiency signal.