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Why Do Dogs Throw Up After Eating Grass

A pet lover passionate about educating readers about animal health and care. Love reading studies and recent research.
Published on
Sunday 8 January 2023
Last updated on
Tuesday 9 May 2023
Why Do Dogs Throw Up After Eating Grass
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Dogs evolved ever since their domestication process. Yet, until now, they’re still interesting creatures. We thought that our fellow canines are carnivores. Well, they must have undergone drastic changes because we see them munching on grasses now. Anyway, why do dogs eat grass and vomit? Is this one of their nature? 

8 Reasons Why Do Dogs Eat Grass and Vomit

A survey in 2007 about animal behavior concluded that dogs have a natural behavior to eat plants. Researchers reported that among the 47 pet owners, 79% or 37 of them said that they saw their dogs eat plants.

In another survey that has 3340 respondents, 68% of dogs reportedly eat grass daily. Also, researchers stated that 8% of dogs were already ill before grass consumption. Moreover, 22% of those dogs vomited after eating grass.

Hence, one reason why dogs eat grass and then throw up is because of age.  Well, younger dogs appeared fine after eating grass while older dogs vomited. Also, for further reference, check out the other reasons why dogs eat grass and vomit below.


Domestication played a huge part in the change in dogs’ behavior. Ancient dogs are carnivorous animals with wide jaws and large cutting teeth. Yet, during these modern times, canines evolved with smaller jaws and teeth and became omnivores. According to science, dogs developed multiple amylase genes. Well, those genes are responsible for an animal’s starch digestion.

Meanwhile, most owners complain about why their dog is eating grass and vomiting. Even though dogs are omnivores, still some of them can’t digest starch or cellulose in the grass. As a result, vomiting removes the remnants of undigested food.


Grass eating is normal behavior for dogs. Yet, too much of it can cause digestive blockage since dogs don’t have the right stomach to dissolve raw ingredients. Moreover, boredom is one of the causes that lead to this grass-eating behavior.

Well, bored dogs will play or eat anything just to pass time. Moreover, that grass-eating behavior, especially if too much, may trigger the vomiting reflex found in the brainstem.

Stress or Anxiety

Many pica eating disorders came from stress and anxiety. Pica refers to the repetitive eating of nonfood objects. Although grass is not harmful to dogs, vets still don’t prefer dogs to eat it. Also, when dogs have pica, they will most likely eat or gnaw at the stuff they’ve never tried before.

Same with humans, dogs who have pica are at risk of eating poisonous things. Also, pica is associated with other eating disorders such as anorexia and bulimia. So, when your dog is throwing up grass due to its pica disorder, don’t panic. Instead, book a vet’s appointment to assess your dog’s health.


A study in 2014 about wolves’ dietary nutrition stated that they have tendencies to eat grass. Researchers didn’t think that wolves are interested in plants, but the results stated that their stomachs have plant residues. Also, scientists found out that 32.6% of fecal samples contained grass and sedges. To be precise, that’s at least 0.1 to 3% of plant residue per dog.

Moreover, grass eating can be related to a wolf’s instinct to subdue intestinal worms, such as tapeworms and roundworms. As a result, vomiting removes those parasites. Also, since modern canines came from wolves, it’s no wonder that dogs are eating grass and throwing up as well.

Taste Preference

Most people think some dogs will eat grass because they think they’re food. Then, they will throw it up because it doesn’t taste like their usual food. Well, on the contrary, dogs have food preferences that differ completely from humans.

It turns out that dogs are naturally attracted to grass. Like wolves, dogs consume some grass as additional fiber supplements too. Yet, if that grass has insecticides, then it can induce vomiting in dogs. Further, insecticide poisoning is rampant in dogs who like eating grass.

Dietary Response

Dogs act based on their nutrient loss. It turns out that when they lack dietary supplements; they make up for them by finding alternative sources. For instance, dogs need fiber because it aids with their digestion. So, when dogs don’t have enough of that, they eat grass.

According to a study in 1997, plants are a great source of fiber. It even has more fiber compared to legumes, but it’s only slower to digest. Dogs, although they eat grass fiber, are non-ruminants. Hence, the reason why dogs are throwing up eating grass is that they don’t have the proper stomach to digest it.

Upset Stomach

Another reason why dogs eat grass and vomit is that they’re sick. Dogs are animals that self-medicate. They cannot speak, so they’ll most likely try to cure themselves. Well, dogs think that eating grass can induce vomiting that will rid them of unwanted substances in their stomachs.

Meanwhile, a 2019 gastrointestinal disturbance study about dogs stated that grass is not used for canine self-medication. According to the results, among the 374 grass-eating sessions, only 2 sessions showed vomiting. Also, it was found that dogs ate more grass when fed with the usual standard diet compared to the fructooligosaccharides diet.

Other Digestive Issues

The reason why your dog is eating grass and throwing up is because of high amylase enzymes. Amylase is the one responsible for turning a grass’ starch into small units that are used for energy. When dogs eat so many plants, more amylase enzymes work to break down the starch.

Further, high amylase enzymes are associated with pancreatitis. Take note that a malfunction in the pancreas also means a decrease in amounts of insulin. Without the proper amount of insulin, a dog’s blood sugar levels may become too high and thus, causes vomiting after eating.

Is It Safe For Dogs To Eat Grass

The grass is usually safe for dogs to graze.  Yet, as owners, just ensure that your dog has updated vaccines and deworming sessions since some zoonotic diseases stick to the grass. Hence, your pet can be at risk of possible contamination. Also, ensure grazing is only minimal since some dogs eat grass and then throw up. 

Also, in another study about dogs’ grass-eating behavior, it was found that puppies learned that grass is edible through their mothers. According to the results, puppies ate more grass when they saw their mom eating as well. Further, when they become weaned, they consider grass as food.

Further, wheatgrass is one of those safe grasses that dogs like to eat. This grass has lots of fiber, vitamins, and enzymes that are essential for a dog’s health. On the contrary, most, but not all plants are safe. For instance, grass-like foxtail plants are dangerous since they carry toxins that irritate them.

Grass Safe For Dogs To Eat

Grasses serve not only as lawns but also give health benefits to dogs. Well, they provide a soothing playground for your pet and help reduce anxiety. As an owner, you may wonder what to do when your dog eats grass during one of its playtimes.

You don’t have to worry anymore since here is the list of safe grasses that your dogs can eat and play with. Check them out below.

  • Agropyron repens
  • Dill
  • Fennel
  • Basil
  • Thyme
  • German Chamomile
  • Spider Plant
  • Horsetail
  • Lavender
  • Nasturtium

Unsafe Grass For Dogs

As owners, you need to be vigilant since not all plants or grasses are safe. Sometimes dogs eat toxic grasses and vomit. Well, in worse cases, poisoning and infection can happen which can lead to serious health issues.

Moreover, below is the list of unsafe grasses owners need to keep away from their dogs.

  • English Ivy
  • Lily of the Valley
  • Foxglove
  • Horse Chestnut
  • Chrysanthemum
  • Nerium oleander
  • Autumn crocus
  • Pampas grass
  • Cheatgrass
  • Downy Brome

How Do I Stop My Dog From Eating Grass

Nutritional deficiency is the main cause of most dogs’ eating disorders. Most likely dogs will start eating grass, then throw up if they’re missing fiber in their diet. Moreover, in a similar study, an 11 male Poodle had the same dilemma. It kept throwing up after eating grass every day for 7 years. Yet, when the owner switched to a high-fiber diet, the dog simply stopped its grass-eating behavior.

It’s been a common medical myth that grasses are anti-parasite. Many owners thought their dogs eat grass to reduce intestinal tapeworms and roundworms. Although there aren’t studies that prove that claim, it won’t hurt to at least book an appointment with your dog’s vet. Also, to be sure, update your dog’s deworming sessions.

Moreover, canines will entertain themselves if they’re feeling alone, stressed, or anxious. When that happens, dogs will bite stuff or eat grasses to relieve their boredom. Well, that behavior can give way to another eating disorder called pica. To fix that, make sure to never leave your dog alone for hours. Then limit his exposure to grasses and ensure that he gets the proper exercise every day.

Further, another way to distract your dog from eating grass is to play exciting games with him. Keep him busy with puzzles, or play fetch with him. Also, this could be the perfect time to take him out for long walks and teach him new sets of commands.

Most of the time, dogs eat grass and vomit because of their owners’ neglect. Well, canines will only nibble something if they’re hungry or bored. Hence, dogs won’t bother to bite grasses if their owners give them a high-fiber diet and also, enough attention. Yet, to ensure that there’s nothing wrong with your dog, bring him to a veterinarian.

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