Why Does My Dog Eat Grass? Common Reasons and When to Worry

Many dogs eat grass, and in most cases it is normal and not a sign of illness. The cause is often boredom, habit or simply liking the taste, though some dogs eat grass when their stomach is upset or their diet lacks fiber. Call your veterinarian if the grass eating is frequent, sudden, comes with vomiting, diarrhea, lethargy or loss of appetite, or if the grass may have been treated with chemicals.

Common reasons dogs eat grass

Veterinarians and animal behavior experts do not agree on a single cause, and several explanations may apply. These are the most widely accepted ones.

It is a normal dog behavior

Eating grass is common in healthy dogs of all ages. Dogs are natural scavengers, and many chew and eat plants, grass included. A dog that eats a little grass, seems happy and has normal stools and appetite is usually fine.

Boredom, attention or anxiety

Dogs that are bored, under-exercised or anxious may eat grass as something to do. A dog may also learn that grabbing grass gets attention from the owner. If the behavior happens mostly when the dog is left alone or in the yard without activity, more exercise, play and mental stimulation may help.

Dietary needs and fiber

Some dogs may eat grass because their diet is low in fiber or because they enjoy the texture. Switching foods should only be done on veterinary advice, and any change should be made gradually over about a week to avoid stomach upset.

Upset stomach

Some owners notice that their dog eats grass and then vomits. It is not clear whether dogs deliberately eat grass to make themselves sick. In fact, many dogs eat grass and do not vomit at all. If your dog eats grass in large amounts, seems nauseated, drools, licks lips or gulps, or vomits repeatedly, something other than habit may be going on.

Taste and enjoyment

Some dogs simply like it. Young fresh grass in spring can be especially appealing.

When grass eating is a reason to call the vet

Contact your veterinarian if you see any of the following:

Your dog suddenly starts eating much more grass than before.
Grass eating comes with repeated vomiting, diarrhea, blood in the vomit or stool, or black, tarry stools.
Your dog is lethargic, loses its appetite, loses weight or seems to be in pain.
The abdomen looks swollen or your dog is restless and unable to settle.
Your dog drinks or urinates much more than usual.
Your dog is a puppy, a senior or has an existing health condition.

Frequent grass eating together with these signs can go along with problems of the stomach or intestines, but only a veterinarian can find the cause. Do not try to diagnose or treat your dog yourself.

If your dog is retching without bringing anything up, has a swollen belly, is collapsing or is very weak, go to an emergency veterinarian immediately.

Is eating grass dangerous?

Grass itself is usually harmless, but the risks come from what is on it or in it.

Lawn chemicals: Herbicides, pesticides and fertilizers can be toxic to dogs. Keep your dog off lawns that were recently treated and follow the product label for how long to wait.
Parasites: Grass contaminated with feces from other animals can carry intestinal worms and other parasites. Keep your dog on a regular parasite prevention plan as your vet advises.
Toxic plants: Dogs that eat grass may also nibble other plants. Some garden plants, including sago palm, oleander and certain lilies, are poisonous. If you think your dog ate something poisonous, call your veterinarian, an emergency clinic or the ASPCA Animal Poison Control Center right away.
Foreign objects: Sticks, stones or litter in the grass can be swallowed and cause a blockage.

What you can do at home

Watch and note the pattern. Note how often your dog eats grass, what time of day, and whether it vomits afterward. This is useful information for the vet.
Provide more exercise and play. Daily walks, fetch, sniffing games and puzzle feeders can cut down on boredom-driven grazing.
Check the diet. Make sure your dog eats a complete and balanced food suited to its age and size. Ask your vet before changing the diet or adding supplements.
Offer safe alternatives. Some owners give dog-safe chews or a pot of pet-safe grass grown indoors.
Use a leash and redirect. On walks, call your dog away from grass in areas that may be treated or contaminated. Reward it with a treat when it comes to you.
Teach “leave it”. This is a useful cue for grass, litter and anything else you do not want your dog to eat.
Keep up with parasite control and vaccines. Follow your vet’s schedule.

Common mistakes

Scolding or punishing the dog. It can make the dog anxious and does not address the cause.
Assuming grass eating is always a sign of illness, or assuming it is never a problem.
Giving human medication for an upset stomach. Many human medicines are harmful to dogs. Only use what your vet recommends.
Letting the dog graze on lawns treated with chemicals or in places where other dogs relieve themselves.

Quick answers

Does eating grass mean my dog has worms?

Not necessarily. Grass eating alone is not a reliable sign of worms. If you see worms in stool, or your dog has diarrhea, weight loss or a dull coat, ask your vet about a fecal test.

Why does my dog eat grass and then throw up?

Some dogs vomit after eating grass because the blades irritate the stomach lining. Occasional vomiting after grazing may not be serious, but if it happens often or your dog seems unwell, see your vet.

Should I stop my dog from eating grass?

If the grass is untreated and your dog is healthy, a little grazing is usually not a concern. Stop your dog if the grass may have been treated with chemicals, if it is excessive, or if your vet advises it.

Do puppies eat grass more?

Puppies explore the world with their mouths, so grass eating is common. Keep an eye on them, as puppies are more at risk from parasites and toxins, and speak to your vet if you are worried.