Why Do Dogs Eat Grass? What Research Says and When to Worry

Most dogs eat grass because it is a normal dog behavior, not because they are sick. Researchers at the University of California, Davis, surveyed dog owners and found that plant eating is very common in healthy dogs and usually is not followed by vomiting.

That said, a sudden change in grass eating can be a clue that something is wrong. Here is what the research shows, the most likely reasons, and when to call your vet.

What the research found

The best known study on this topic was led by veterinary behaviorist Dr. Benjamin Hart and his team at UC Davis. Their web based survey included 1,571 dog owners whose dogs had regular access to plants.

The researchers also found that younger dogs ate plants more often and were less likely to seem sick before or vomit after. They found no clear link between plant eating and the type of diet or the amount of fiber the dog ate.

Their conclusion: grass eating is a common, normal behavior in dogs, and vomiting seems to happen alongside it rather than being the reason for it.

The most likely reasons for grass eating

1. It is an inherited habit

The UC Davis researchers pointed out that wild relatives of dogs, such as wolves, also eat plants. One theory is that plant eating helped wild canines pass intestinal worms. Our pet dogs may keep the instinct even when they do not need it.

2. They like it

Many dogs seem to enjoy the taste or texture of fresh grass, especially new spring growth after rain. If your dog picks grass carefully and chews it calmly, that is probably the reason.

3. Boredom

Dogs that do not get enough exercise or mental activity sometimes find their own entertainment. Grazing in the yard can be one of those self made activities.

4. An upset stomach (sometimes)

A small number of dogs do eat grass when their stomach feels off. These dogs usually gulp grass quickly rather than nibbling, and may vomit soon after. This pattern is the one worth paying attention to.

Normal grazing or a warning sign?

Eating non food items on a regular basis is called pica. It can be linked to medical problems such as gut disease or nutrient issues, or to stress, so it is worth a checkup.

The real risks of grass eating

The grass itself is rarely the problem. These are:

• Lawn chemicals. Weed killers, fertilizers, and pest sprays can make dogs sick. Keep your dog off treated lawns until the product label says it is safe, and avoid unknown lawns on walks.
• Toxic plants. Grass areas can include harmful plants. The ASPCA keeps a searchable list of toxic and non toxic plants.
• Parasites. Grass where other dogs have pooped can carry worm eggs. Keep your dog on regular parasite prevention and avoid heavily used patches.
• Grass awns. Sharp seed heads, often called foxtails, can lodge in the nose, ears, paws, or throat. Sudden sneezing, head shaking, or a swollen paw after a walk needs a vet visit.

How to reduce grass eating (if you want to)

You do not have to stop normal grazing on safe, untreated grass. But if your dog overdoes it:

1. Add more exercise. Longer walks, fetch, and play sessions burn energy.
2. Add brain games. Food puzzles, snuffle mats, and short training sessions help with boredom.
3. Offer a safe alternative. Some owners grow a pot of dog safe grass, such as wheatgrass, indoors.
4. Teach "leave it." Reward your dog for walking past the grass with you.
5. Use a leash on walks so you can steer away from treated or unknown areas.

When to call your vet

Call soon if your dog:

• Suddenly starts eating grass much more than usual
• Vomits more than once, or vomits for more than a day
• Seems tired, stops eating meals, or loses weight
• Has diarrhea or blood in the stool
• May have eaten grass treated with chemicals, or a plant you cannot identify

What to tell your vet

If you do call, a few details make the visit faster and more useful:

• How long the grass eating has been going on, and whether it suddenly increased
• How your dog eats it: slow nibbling or fast gulping
• What happens after: vomiting, how often, and what the vomit looks like
• Stool changes: diarrhea, mucus, blood, or very dark stool
• Appetite and energy at mealtimes and on walks
• Where it happened: your own yard, a park, or a lawn that may have been treated
• Diet changes: new food, new treats, or table scraps in the past week

A photo of the plant your dog was eating, or of anything unusual in the vomit, can also help your vet decide what to check first.

The bottom line

For most dogs, grass eating is just part of being a dog. Keep the grass clean and chemical free, watch for changes, and call your vet if grazing comes with vomiting, diarrhea, or a dog that seems unwell.

Want to understand other dog quirks? A calm walk is a great place to watch your dog's behavior. See our guide on how to stop a dog pulling on the leash.