Why Does My Pet Eat Grass?
What the research found for dogs and cats, in plain words.
The short answer
It is usually normal.
Eating grass and plants is common in dogs and cats, and it is usually normal behavior. Most pets are not sick when they do it. Read on for what studies of real dogs and cats actually found.
Dogs: what the study found
Researchers at the University of California, Davis, asked dog owners about grass-eating. Their survey was published in the journal Veterinary Medicine in 2008. Here is what they found:
- Most dogs showed no sign of illness before eating grass.
- Only about 22% — about 1 in 5 — vomited afterward.
So the old idea — “he eats grass because he is sick and needs to throw up” — is mostly a myth. Most dogs were fine before, and most did not throw up after.
Cats: what the study found
In 2019, the UC Davis team surveyed 1,021 cat owners who watched their cats at least 3 hours a day. Here is what they found:
- 71% of the cats were seen eating plants at least six times.
- The cat seemed completely normal beforehand 91% of the time.
- About 27% — about 1 in 4 — often vomited afterward.
Just like dogs, cats usually look and act fine before they eat plants.
Why do they do it? A theory
The leading idea is a theory. It has not been proven.
The theory says grass-eating is inherited from wild ancestors. Eating plants speeds up muscle activity in the gut. For wild animals, that may have helped clear out intestinal parasites — worms living in the gut. Our pets may still carry the habit, even when they have no parasites. Again: this is a theory, not a proven fact.
There are simpler reasons too, especially for cats:
- Cats cannot digest plant material well, so grass mostly passes through. (Cornell Feline Health Center)
- Some cats may simply like the taste or the feel of it.
- Boredom can play a part, especially in indoor cats.
⚠ The real danger is what is ON the grass
The grass itself is usually not the danger. The danger is what may be on it:
- Lawn weed-killers
- Pesticides (bug sprays and treatments)
- Fertilizers
- Toxic plants — some plants are poisonous to pets
The ASPCA keeps free lists of plants that are toxic and not toxic to pets, so you can check a plant before your pet gets to it.
If you think your pet ate a treated lawn or a toxic plant, act right away. Call your veterinarian, or call the ASPCA Animal Poison Control Center:
(888) 426-4435That is the ASPCA Animal Poison Control Center number.
What you can do
The Cornell Feline Health Center suggests these simple steps:
- Offer cat grass grown at home. Kits grow oat, wheat, or barley grass. It gives your cat a safe plant to nibble, grown without lawn chemicals.
- A higher-fiber food sometimes helps. For some cats, it reduces grass-eating.
- Play more. If boredom is the cause, more play time can help.
See a veterinarian if you notice…
Grass-eating by itself is usually normal. But talk to a veterinarian if you see any of these:
- A sudden big increase in plant-eating
- Vomiting again and again
- Not eating
- Weight loss
- Seeming tired or unwell
- Eating lots of things that are not food at all
Sources: University of California, Davis, School of Veterinary Medicine — survey research by Dr. Benjamin L. Hart and colleagues (dogs: Veterinary Medicine, 2008; cats: 2019) · Cornell Feline Health Center · ASPCA (plant lists and Animal Poison Control Center). Checked November 2026.