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Why do Dogs Eat Grass?

Recently, my co-author Dr. Jean Dodds, wrote a fantastic article on Why Dogs Eat Grass. Since I am often asked this question by clients – and many take it as a sign of concern – I wanted to share this article with you today. So, let’s take a look as Dr. Dodds unpacks the latest scientific research on this topic for us. Hopefully, this will put you more at ease the next time your dog munches on your lawn!

why do dogs eat grass

By Dr. Jean Dodds

“Why do dogs eat grass?” My veterinary colleagues and I are asked this frequently and we honestly do not know the exact reason or reasons. To try to answer this age old question, a few studies have been conducted.

Australian Study

Researchers at the University of New England in Australia compared two sets of dogs. One set of dogs was given a diet supplemented with fructo-oligosaccharide (FOS), which temporarily can induce loose stools and mild gastrointestinal (GI) distress.

The researchers observed that the group not fed the FOS diet and with normal stools actually ate grass for longer periods of time. In this particular instance, the team determined that dogs apparently do not eat grass to self-medicate for this form of GI distress. They were quick to note, however, that grass eating may occur for self-medicinal purposes for other types of potential GI disturbance episodes.

Importantly, this team of researchers only observed two vomiting episodes after grass eating, which led them to conclude that dogs do not eat grass to induce vomiting.

UC Davis Study

Another team of researchers at the University of California, Davis conducted three separate surveys. Their hypothesis was, “Most plant eating in dogs is associated with illness or a dietary deficiency and that ingestion of plant material is usually followed within a few minutes by vomiting.”

First Survey – Veterinary Students

Sample size = 25

  • All students reported that their companion dogs ate grass.
  • Zero reported signs of illness before the grass-eating event.
  • Two students said that their dogs frequently vomited afterwards.

Second Survey – Teaching Hospital Clients

Sample size = 47

  • 37 had seen their dogs eat grass.
  • 33 owners answered questions about their dogs’ behaviors before and after eating grass.
  • Four of the 33 reported signs of illness preceding the events.
  • Six of the 33 reported occasional vomiting afterwards.

Third Survey – Web-Based

Sample size = 1,571

  • 1,068 said their companion dogs ingested plants daily or weekly.
  • 126 (8%) indicated that their dogs frequently showed signs of illness before plant-eating.
  • 346 (22%) reported regular vomiting after plant eating.
  • Of the 1,068, younger dogs were more apt to eat plants rather than older dogs, and did not appear ill beforehand or vomit afterward.
  • If dogs showed signs of illness before eating, they were more likely to vomit afterwards.

The survey from the team at UC Davis asked specific questions relating to diet. They determined that diet – which varied from kibble to raw – did not impact the plant eating. Additionally, dogs receiving less fiber in their diets did not tend to eat more grass than dogs getting more fiber.

They concluded, therefore, that grass eating is a common behavior in apparently normal dogs that is unrelated to illness or vomiting.

Of course, their caveat was that a subclinical GI distress may provoke grass eating occasionally. Indeed, pet caregivers that have contributed to our NutriScan Case Studies have stated that before the food sensitivity testing was conducted, they believed their dogs ate grass to calm their stomachs. After adjusting their diets according to the Nutriscan results, caregivers noted that the diet change helped curb or stop the grass eating habit.

The UC Davis team’s current hypothesis is that plant eating helped our canine and feline ancestors purge nematodes (intestinal parasites). This habit has been observed in chimpanzees because the plant leaves increase bowel motility, can wrap around the nematodes and thus flush them out of the body. They also correlated this hypothesis with younger dogs eating plants more often than older dogs because they are less resistant to intestinal parasites. This fascinating theory truly needs to be studied. And who knows? Perhaps we could replace some conventional dewormers with plant-based options. Please note: this comment is not meant as a suggestion that you give your dogs plants in lieu of intestinal dewormers. We need to wait for research clinical trials to be conducted.

In the meantime, let’s just let your dog do what comes naturally.

W. Jean Dodds, DVM
Hemopet / NutriScan
11561 Salinaz Avenue
Garden Grove, CA 92843


I hope you enjoyed this informative article by Dr. Dodds on Why do Dogs Eat Grass? and that, as always, it helps you and your canine companion to enjoy many healthy, happy years together.

Does your dog eat grass? If so, when? Please share your canine grass-eating experiences in the comments below this post!


Hart, Benjamin L. “CVC 2008 Highlights: Why Do Dogs and Cats Eat Grass?” N.p., 01 Dec. 2008. Web. 13 May 2017.

McKenzie, Samantha, Wendy Brown, and Ian Price. “Reduction in Grass Eating Behaviours in the Domestic Dog, Canis Familiaris, in Response to a Mild Gastrointestinal Disturbance.” Applied Animal Behaviour Science 123.1-2 (2010): 51-55. Applied Animal Behaviour. Web. 13 May 2017.

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  1. Susan Horak says:

    My border collie eats grass almost daily. He never throws it up nor is he sick before eating it. He just likes grass!

  2. Sonya Dorr says:

    I believe that my Golden Retrievers are closely related to horses, or goats! Especially in the spring when the grass is just sprouting they graze just like horses 🙂 They LOVE grass! I have not used any chemicals/fertilizers on my yard for years so they are not ingesting them. Sometimes I have seen vomiting afterwards, but most times not. I figured they were trying to get more fiber or they just like it.

  3. jan kase says:

    My 3 dogs and I have been living in a community that does not plant grass. All the property owners line their lots with pea gravel to avoid watering and cutting grass. Therefore, on our neighborhood walks, only two homes have grass. Therefore, my dogs love to roll in it, and chew on the grasses. No upset tummies, no throwing up, just enjoying (I imagine) the taste, the moisture in the grass, and something natural that is not provided by the unwanted pea gravel.

  4. Hollae Larson says:

    Even though both our 10 year old dogs (a male Shit-zu & a female, 1/2 Tibetan Spaniel/Shit-zu) are fed a lightly cooked fresh food diet combined with Dr. Peter Dobias’s Green Min, Soul Food and Gut Sense Probiotics………they still eat grass! At the time of writing this note, they are not displaying any signs of illness. However, they most certainly are not allowed to munch on any grass coated in toxic chemicals.
    Their diet includes a considerable amount of fiber and a thorough attempt is made to balance nutrients on a weekly basis. Their all organic diet includes spinach, dandelion greens, chard, etc. etc. etc. They most certainly are not lacking greens! But, if fresh, they still eat a little grass AND ALWAYS HAVE!!! We live in Calgary, Alberta, Canada so grass is simply not always available. But when it is………..they are on it. No vomiting occurs afterward.
    This is a rather interesting habit; one that begs an answer.
    Thank-you Diana and Dr. J. Dodds for your concerted effort to research canine issues and educate us all!

  5. Sunniva Bjørndal says:

    Sometimes my dogs eat grass to cure nausea, then the grass eating is rather frantic and usually after a car ride, or some kind of stress source, like pulling to hard in the harness due to forest animals in front of them, and when they get to hot from this activity. Vomiting occurs most times. But every spring some dogs eat grass just for the pleasure, first straws up are found and eaten, then vomiting never occurs. And a few times the dogs walk around the garden picking at high grass, that are rather sharp, and this i clearly to induce vomiting, their system get in touch with a lot of different bacteria, and I guess that it is clever enough to know when to eliminate something that should not go further down. Back in the days when we fed dry pellets I observed some panic nausea attacks that made them search for something to eat real fast and would take any houseplant or dry hay in order to vomit…I have never seen that since, it might have been bacteria or the damage effect from a lot of dry food soaking up the stomach acid. I also do not think we should eliminate the fact that their natural pray animals eat grass, and that a part of the grass feeding is a attempt to make up for the fact that they now a days do not get to eat hole fresh killed prey that still has grass in their digestive tract. Because fresh grass is not partially digested like it is in the prey, then it might be much worse for the stomach to tolerate. Just some thoughts I wanted to share, Love from Sunniva

  6. All our past dogs ate grass. Most vomited afterward. All past dogs ate kibble except for the Chihuahua who had home cooked minced beef stew. No supplements, just browned hamburger, carrots, onions & peas…sometimes some fresh garlic. All stewed. Yet this dog lived to be past 16 years old & died of a heart attack. She weighted 3 lbs all her life. She is the one who very rarely ate grass.
    Our present dog, a black Lab, has had either food allergies or intolerances all her life. NutriScan did not help. We are pretty sure she has leaky gut syndrome. She is on a single protein raw diet with greens, probiotics, digestive enzymes & a green-lipped mussel supplement for joints. She is 15. If this dog does not have her breakfast & dinner at approximately the same time every day, she experiences gut problems. If we feed her dinner too early in the day, we can guarantee that about 5 a.m. the next morning she will come to us with the noisiest stomach you ever heard & insist on going outside. Once out, she grazes like a goat on grass. Naturally we don’t like waiting at the door for her while she grazes at 5 a.m. so we eventually bring her in & either feed her or give her a little something so we can go back to bed. On these occasions, she never vomits. Rarely she has eaten grass at other times & has vomited an hour or so later, but this is not a result of having her food too early.
    Tis a mystery indeed.
    We are grateful for all animal lovers like yourselves for exploring all the behaviours of our beloved pets. I say, “Let them eat grass!”

  7. My 9 yrs St. Bernard/ Labrador eats grass with great passion 1-2 x/week and vomits 2-3x about 1-2 minutes after. In my perception he feels better “flashing out his stomach”: becomes more energetic, happy. He eats grass only on certain days, and not all type of grass.
    I would be incline to support theory of “self- help/cure”, since “mother nature” has developed it many forms……. animals frequently living in extremely hostile environment would not survive without self preserving mechanisms. I do not try to stop my dog since “grass stomach cleaning” habit seems to be beneficial, not dangerous. We have to be humble in our interpretation of our canine friends’ behavior. This issue is interesting and require further studies.

  8. Several years ago when I had 3 adult male Irish setters at one time, every morning when I let them out in the yeard before breakfast, the three of them would graze like cows. Only one of them would vomit it up each time. The all three would proceed to eat breakfast which consisted of a holistic kibble and fresh meat as a topper. They ate 2 x’s a day; two lived to be 14, one lived to be 16. They never had GI problems at all.
    My latest Irish, now 2 1/2 had digestive problems (gurgling intestines, bloody stool) since he was 7 mos. old. Each time he would have an episode, he would eat grass and later he would have very loose stool, usually with blood. He was on various premium kibble diets, to no avail and a proscription vet diet, which was worse. Then he finally got on a home cooked real food diet (thank you, Diana!) and now he doesn’t eat grass anymore. Interestingly, three of these dogs were from the same breeder, including my current boy. Weird.

  9. Thank you for this article. My pup of 14 has eaten grass since I brought him home at 3 months of age. It has decreased a great deal through the years as I’ve become educated on nutrition and changed his diet and continue to change it as I learn more. But I have to wonder is it the diet or the fact we are not tromping thru trails and woods for an hr a day because he is now a golden 14 yrs old. Our adventures now involve daily short walks in the addition where the tall green Prarie type grass he enjoys isn’t available. Yet if a patch of crab grass presents itself he will grab a mouthful. It’s funny he definitely had a type of grass he goes for. But never has he vomited from it. I really think he simply enjoys the taste. Strange as that sounds. This article helps me remember he is healthy, has always done this, and that this is his norm. Nothing out of the ordinary!

  10. Even my dog eats grass, but haven’t shown any sign of illness yet. I think they just like to eat grass. Moreover, I ensure they eat grass only from our yard as I don’t use fertilizers on it. So I know they are not consuming chemicals.