Why Do Cats Eat Grass?

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Cats are quirky creatures with many curious habits, but one odd behavior that has long puzzled cat lovers is grass eating. Though indoor-outdoor cats obviously have more access to the green stuff, even indoor cats are known to nibble on blades of grass if they go outside for some fresh air or to explore.

Cats are obligate carnivores, which means they are biologically designed to eat a primarily meat-based diet. Although cats can the digest grains, fruits, and vegetables found in commercial cat food, cats are not true omnivores, so plant material like grass would not be part of their diet in the wild.

And it would seem that grass might not agree with a cat’s digestive system since some cats that eat grass promptly throw it up a short while later.

So why do cats eat grass?

Theories About Why Cats Eat Grass

The answer eluded scientists for ages, but a recent study may have gotten to the bottom of this feline idiosyncrasy. Before we get to that, let’s recap some of the long-held theories about why cats eat grass.

Nutritional boost: One theory suggests that cats eat grass because they are lacking certain nutrients or enzymes in their diet. Grass does contain folic acid, but the jury is out on the idea that cats intuitively know that they need a top up on folic acid.

Upset stomach relief: Cats sometimes vomit after consuming grass. Another theory about why cats eat grass says that cats know they will throw up after a grass snack, so if they ate something that did not agree with them or are otherwise feeling unwell, they might attempt to induce vomiting by eating grass.

Natural laxative: It’s possible that eating grass could help to ease constipation or aid in hairball removal. Grass contains a lot of fiber, so it could get things moving in the right direction.

Cat eating grass

Although there are several theories, we don’t know for certain why cats eat grass.

A New Theory About Why Cats Eat Grass

Recently, researchers at the University of California, Davis, School of Veterinary Medicine conducted an online survey of more than 1,000 cat owners asking about their cats’ penchant for eating grass and plants. The findings, presented in summer 2019 at the annual meeting of the International Society for Applied Ethology in Bergen, Norway, revealed some interesting facts about cats eating grass.

First, eating plant material is very common: 71 percent of cats in the study nibbled plants at least six times in their life, and 61 percent ate plant material at least 10 times. Another finding was that most cats (91%) were acting normally and did not appear to be sick in the time immediately preceding the grass eating. Of all the cats that ate plant material, only about 27 percent frequently vomited after eating the green stuff.

Based on these results, the researchers hypothesized that cats don’t eat grass as a way to naturally treat an upset stomach. Instead, the scientists believe that cats might instinctually eat grass and other plant matter to rid themselves of intestinal parasites—a behavior that has been observed in wild carnivores and primates. Eating vegetation might trigger the digestive tract to physically expel troublesome parasites.

Is Grass Safe For Cats?

Whatever the reason, many cats do eat grass on occasion. But do you need to be concerned if your cat nibbles on the green stuff now and again?

Yes and no…

Eating grass can cause mild stomach upset, which is why some cats vomit after eating grass, but grass in and of itself is not generally dangerous to cats. In fact, the right type of grass is even considered a safe and nutritious snack for cats.

However, the danger comes from what might be on the grass your cat is consuming. Lawn fertilizer, weed killer, pesticides, and other chemicals used on lawns can be very dangerous to your cat, even in small amounts.

Cat grass

Mild stomach upset or a little vomiting is typical when cats eat grass.

What To Do If Your Cat Eats Grass?

If your cat eats grass in your yard, keep an eye on her to make sure she isn’t displaying any signs of illness. This is especially important if you use any chemicals on your lawn like fertilizer, herbicides (weed killer) or pesticides.

If your cat throws up after eating grass, make note of how many times she vomits.

Call your veterinarian if she keeps throwing up, or if she is displaying other symptoms like diarrhea, lack of appetite, lethargy (no energy), seizures, tremors, foaming at the mouth or any other signs of illness.

Other Plants And Flowers

Although grass is not dangerous for cats to eat, other plants are very toxic to cats. Cats that like to eat grass might also try to munch on houseplants and flowers, which can have deadly results.

Some plants cause mild issues in cats like mouth irritation or stomach upset; others can cause severe vomiting and diarrhea, seizures, kidney failure and death.

Many plants and flowers are toxic to cats, but some of the most dangerous include all types of lilies, autumn crocus, azaleas, rhododendrons, oleander, cyclamen and daffodils. Keep only non-toxic plants, greenery and flowers in your home.

If you suspect your cat may have eaten part of a toxic plant or flower (or even just licked water from the vase of a dangerous plant), contact your veterinarian or an animal poison-control hotline right away.

Cat eating grass

Cat grass is easy to grow and safe for cats to eat.

How Cats Can Eat Grass Safely?

If your cat likes to eat grass, but you’re worried about her consuming dangerous lawn chemicals, you might consider purchasing some special grass for your cat to safety snack on. Cat grass (sometimes called kitty grass) is a safe grass blend meant to be grown indoors.

Lightly water the grass container, put it near a window for indirect sunlight and let it sprout. Your cat will love munching the grass that grows, and you can rest easy knowing it doesn’t contain any dangerous chemicals.

Frequently Asked Questions 

Is eating grass bad for cats?

Cats can't really digest grass, so eating grass can cause mild stomach upset, such as vomiting. However, grass is not generally dangerous to cats. However, cats can become very sick from eating any grass treated with lawn fertilizer, herbicides (weed killer), pesticides or other chemicals.

What does it mean when a cat eats grass?

No one knows the true reasons cat eat grass, but some theories say that cats might eat grass to relieve an upset stomach, to obtain nutrients lacking in the diet, to ease constipation or move hairballs through the intestinal tract, or to purge their bodies of intestinal parasites.

Do cats eat grass when they are sick?

A recent study suggests that cats don’t eat grass if they are sick. However, eating grass can cause a cat to suffer mild stomach upset, including vomiting. 

How often should cats eat cat grass?

Cats can nibble on cat grass as often as they like, and many owner leave trays out for their cats to visit as they desire. If you notice that your cat is eating too much grass and suffering excessive stomach upset, you can limit her grass consumption to just a few times a week. 

Does cat grass make cats vomit

Cats sometimes vomit after consuming grass. Another theory about why cats eat grass says that cats know they will throw up after a grass snack, so if they ate something that did not agree with them or are otherwise feeling unwell, they might attempt to induce vomiting by eating grass

About Jackie Brown

Jackie Brown is a content creator specializing in the pet industry. She writes on all pet and veterinary topics, including general health and care, nutrition, grooming, behavior, training, veterinary and health topics, rescue and animal welfare, lifestyle, and the human-animal bond. Jackie is the former editor of numerous pet magazines and is a regular contributor to pet magazines and websites.

2 thoughts on “Why Do Cats Eat Grass?

  1. shirley mcdermott

    My cat eats lots of grass outside around my flower garden! and I have seen her twice go to her litter and drag out poop with a whole blade of grass and then rub he bum on the bathroom floor, as that’s where her litter is! Is this normal due to the long blade of grass or does she have worms, because she also eats house flies!

    1. Mallory Crusta

      Hi Shirley, it’s very difficult to say why your cat is scooting after going to the bathroom, but given the information you’ve provided, it does sound very likely that she’s trying to clean off the blade of grass and anything that was stuck to it. Home examination and a trip to the vet can tell you whether or not she also has worms. Wishing you all the best!


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