You are out on a walk. Your dog is having a great time, sniffing everything, being a dog. Then they stop, lower their head, and start munching on grass like they are at an all-you-can-eat salad bar. You panic a little. Are they sick? Are they missing something in their diet? Do I need to call the vet?
I get this question from clients all the time, so let me give you the answer that researchers have actually figured out. And the answer is more interesting than you think.
The Old Theory (and Why It Is Probably Wrong)
For years, the most popular explanation was that dogs eat grass because they feel nauseous and want to throw up. Grass is a natural way to make yourself vomit, right? So the theory was: dog feels sick, eats grass, throws up, feels better.
The problem is that the research does not back this up. In one well-known study, researchers surveyed over 1,500 dog owners about grass eating. Only about 8 percent of dogs showed signs of illness before eating grass, and only about 22 percent of dogs vomited afterward. The vast majority of dogs eat grass and then go about their day like nothing happened. So the “they are sick” theory is mostly a myth.
What Is Actually Going On
There are a few real explanations, and most dogs are doing a combination of them.
They like it. This is the simplest one, and it might be the most accurate. Grass has a fresh, green taste and a satisfying crunch. Some dogs just enjoy it. The behavior is more common in younger dogs and in dogs who are bored or under-stimulated, which suggests it is partly self-rewarding entertainment.
They are omnivores, and grass is on the menu. Dogs are not strict carnivores the way we used to think. Their ancestors were scavengers who ate whatever was available, including plant matter. Modern dogs still have the digestive enzymes to break down some plant material, and grass is a normal part of their ancestral diet. In other words, eating grass is not weird. It is a leftover behavior from being a flexible eater.
They are fiber-loading. Some researchers think dogs eat grass to add roughage to their diet. Grass contains fiber that can help move things along in the digestive tract. If your dog is a little constipated or just feeling slow in the gut, a bit of grass might be their way of self-medicating.
It is instinctual behavior inherited from wolves. Studies of wild wolves have shown that grass shows up in their stool samples regularly. Wolves eat grass. It is part of the wild canid diet. Our pet dogs inherited this from their ancestors, even though their kibble is doing most of the nutritional work these days.
When to Actually Worry
Most grass eating is harmless. But there are a few cases where you should pay attention.
– If your dog is eating grass obsessively and throwing up frequently, that is worth a vet visit. It could point to a gastrointestinal issue.
– If the grass has been treated with pesticides, herbicides, or fertilizers, you do not want your dog eating it. Those chemicals can be toxic.
– If your dog is eating grass and showing other signs of illness (lethargy, not eating their food, diarrhea), that is a vet conversation.
– If you have plants in your yard that are toxic to dogs, watch what they are sampling. Grass is fine. Ornamental plants may not be.
The Grooming Connection
I see a lot of grass and outdoor debris in the van during spring and summer. Grass seeds especially can get stuck in long ears, between toes, and in the undercoat. After a walk in tall grass, it is worth checking your dog’s paws, ear flaps, and “armpits” for stuck seeds and burrs. Left there, they can work their way into the skin and cause irritation or infection.
I have pulled grass awns out of more dog ears than I can count, and it is always a good idea to do a quick brush-out after a grassy walk to get the loose stuff out before it mats up. If your dog is a grass connoisseur and you are tired of the green tint to their mouth, a quick rinse of their face and a brush-out usually does the trick.
Stay fresh and furry, Nicole / Vroom Grooms LLC
About the Author
Nicole is the owner and certified groomer behind Vroom Grooms LLC, a mobile dog grooming service serving Northwest Ohio. She has been certified since 2020 after completing 640 hours of hands-on training, and sees a lot of seasonal coat and skin issues in the van. You can catch her live on Twitch at DogGroomerNIcole, where she streams real appointments and talks about what she is seeing on each dog.
This post was drafted with help from Nagini 🐍, her digital assistant, who keeps the blog running, handles the tech side of the website, and makes sure Nicole spends more time with dogs and less time wrestling with WordPress.