4 Theories Why Dogs Eat Grass and How to Stop It

No one is certain exactly why dogs eat grass, but it probably isn't because they are feeling sick to their stomach.

Updated March 24, 2023
Black pug eating grass

Many dogs love to eat grass, but the old folk wisdom that dogs eat grass to make themselves throw up or relieve an upset stomach turns out to not be true - most of the time. No one is 100 percent sure why dogs eat grass, however. Some dogs probably eat grass just because they like it, and most dogs who eat grass aren't sick. There's more to the story, and some surprising info on this behavior.

Figuring Out Why Dogs Eat Grass

This is a natural behavior that is typically seen in young dogs, but older dogs do it too. Grass is actually not bad for dogs unless it's been treated chemically, but eating too much can lead to intestinal upset and other problems.

Dogs have been eating grass for a very long time, and it's probably not just because they like the taste. In the wild, dogs and wolves would eat grass to help their stomach digest their food. They sometimes also eat grass when they are sick or injured. But why do dogs do it?

corgi eating grass

1. Are Dogs Who Eat Grass Sick?

No, most of the time dogs aren't eating grass to settle a sour stomach or make themselves throw up. A 2007 study that examined why dogs eat grass found that 79% of dogs who eat grass are well-fed, healthy, and 78% of dogs did not vomit after eating grass. The study concluded that grass eating is a normal behavior for dogs, and that in most cases dogs aren't eating grass because they are feeling ill, and further study has reinforced this conclusion.

Fast Fact

Even though most dogs who eat grass aren't throwing up after, and don't appear to be ill, it is possible that minor intestinal disturbance is causing them to eat grass to loosen their stools. One study found that a chemical in grass helped to create looser, more watery stools in dogs.

2. Do They Have a Nutritional Deficiency?

Theories that dogs who eat grass are missing something in their diet are common. However, these theories don't hold up very well, either. First, most dogs are fed nutritionally complete diets designed for canines, and a nutrient deficiency is unlikely in this group. Even dogs lacking fiber in their diet don't seek out grass more than dogs who are fed complete diets. There's just no evidence dogs eat grass because they're nutritionally deficient.

3. Are Dogs Grass Eaters Because of Their Ancestors?

Wolves and other wild canids eat grass periodically, and the reasons for this aren't well understood. This means your pup may be eating grass just because of instinct.

One theory states that dogs eat grass because they are instinctually trying to clear parasites from their intestinal track, as their wolf ancestors would do. This isn't proven, however, and otherwise healthy wolves have more grass in their diets during the summer months. So, yes, dogs may eat grass out of instinct, but we don't exactly know why wolves eat grass in the first place either.

4. Are Dogs Bored or Hungry?

It's possible your dog just likes the taste of grass. They may be eating grass just because they're bored and want a snack, or they're feeling hungry. Watch your dog's behavior, and take note when they eat grass. If you find they're grazing close to dinnertime, for example, they may just be getting hungry.

Should You Allow Your Dog to Eat Grass?

In most cases, it's OK to let your dog have some grass - except in two situations, covered below - as long as they aren't eating a massive amount. Grass probably won't hurt them overall. Just watch their behavior and make sure they aren't showing symptoms of illness. If your dog is frantically eating grass, however, it's a good idea to call your veterinarian and take you dog in for a checkup.

Danger No. 1, Pesticides: Chemically treated grass and lawns are not safe for dogs to eat, for obvious reasons. These chemicals can be harmful to your dog, and you should keep them from eating any grass that is suspect. Pesticide exposure can result in serious health problems for your dog, including lethargy, vomiting and diarrhea, seizures, and in severe cases even death.

Need to Know

Even if your dog doesn't show immediate effects of pesticide exposure, these chemicals could affect their long-term health.

Danger No. 2, Parasites: Although this is unlikely, it is possible for your dog to pick up intestinal worms or other parasites when they're eating grass. The chances your dog catches a parasitic infection from your own lawn is low, but it's a good idea to limit you dog's grass consumption when you're out and about, and especially in places where other dogs have been, such as the dog park.

How to Stop Your Dog From Eating Grass

  • Monitor them when they're outside. Make sure they aren't getting ready to munch on some grass.
  • Redirect your dog. If you see them pulling up some grass for a snack, get their attention, give them a firm "No," and call them over. The idea is to distract your dog.
  • Treat them when they aren't eating grass. After a little bit of time - so that your dog doesn't associate eating grass with getting treats - give them their favorite high-value treat.
  • Give them lots of exercise and stimulation. Tiring your dog out and offering them a lot of enrichment activities will keep their mind off of their bored grazing.
  • Give them a better alternative. If you can, keep a patch of wheatgrass growing around your home, and offer some cut grass with your dog's food, or as a treat. They may come to prefer this better grass.

Consult a Veterinarian

If your dog starts eating grass frequently, then you should talk with your veterinarian about it right away. If your dog is eating large amounts of grass or if they seem sick after eating it, these could be signs of an underlying health condition such as liver disease or pancreatitis. If your veterinarian rules out medical causes, you can then discuss the behavior with a canine behaviorist or nutritionist to determine why your dog is exhibiting this behavior.

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4 Theories Why Dogs Eat Grass and How to Stop It