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Why does my dog eat grass?

By Sorin Vasiliu6 min read

Is it normal for dogs to eat grass?

Yes, for most dogs. VCA says vets get asked about it "all day, every day", a sign of how many dogs do it. PDSA calls it normal behavior and says it's usually no cause for concern.

A 2008 study by Sueda, Hart and Cliff at the UC Davis School of Veterinary Medicine looked at this. In its survey of 47 owners whose dogs had daily exposure to plants, 79% said their dog had eaten grass or other plants. In a larger, online survey of owners of plant-eating dogs (1,571 qualifying responses), 68% of the dogs ate plants daily or weekly. The researchers said their findings support the view that plant eating is a normal behavior of domestic dogs.

Why dogs eat grass: the leading ideas

There is no single answer. As VCA puts it, the question is simple but the answer is not. Here is what the main sources suggest, and how firmly they say it.

IdeaWhat the sources say
Fiber and digestionAKC and VCA suggest grass may add fiber that helps digestion and stool. Both present it as a possibility, and the 2008 study found no sign that dogs on less fiber ate more plants.
InstinctAKC says it "might just be instinct." VCA notes that stool samples show 11–47% of wolves eat grass.
Boredom or anxietyAKC mentions dogs left alone in the yard. VCA adds loneliness and anxiety, and says grass eating is often noted to rise as time with the owner falls.
Taste and textureAKC and PDSA say some dogs simply like it. AKC mentions fresh spring grass and thirst.
Settling the stomachThe sources split. AKC's chief veterinary officer says dogs may eat grass to help release irritating bile. VCA calls self-medication unlikely.
Missing nutrientsProbably not, on a balanced diet. PDSA says it isn't linked to dietary deficiencies, VCA says dogs on balanced commercial diets shouldn't be deficient, and the 2008 survey found no link with diet type. AKC notes a vet may call extreme grass eating pica, which is sometimes caused by a diet deficiency.

None of these is proven, and your dog may have more than one reason.

Do dogs eat grass to make themselves sick?

Mostly not, on the evidence so far. PDSA calls it a common misconception.

In the online survey, only 9% of the dogs were reported to frequently seem ill before eating plants, and only 22% to frequently vomit afterward. Younger dogs ate plants more often, yet were less likely to regularly seem ill first or vomit after. VCA, citing similar figures, concludes that most grass-eating dogs aren't sick beforehand and don't vomit afterward.

Some dogs do vomit after eating grass, and AKC says it's more likely on an empty stomach. Dr. Jerry Klein, AKC's chief veterinary officer, says yellow foam, or bile, usually means the stomach is empty. If that sounds like your dog, AKC suggests talking with your vet.

There is also a chicken-and-egg problem, which VCA points out. The ASPCA notes that eating any plant material may cause vomiting and stomach upset in dogs. So vomiting after grass doesn't prove your dog felt sick before it.

When eating grass can be a problem

The grass itself may not be harmful, VCA says. What's on it, or near it, can be.

  • Lawn chemicals. AKC and VCA both warn that grass treated with herbicides and pesticides can be toxic to dogs.
  • Intestinal parasites. Dogs can swallow roundworms or hookworms left in droppings from other animals, according to AKC and VCA. VCA says occasional grazing is no worry if it doesn't make your dog sick and parasite prevention is consistent. Ask your vet what fits your dog.
  • Lungworm. PDSA, whose advice is for UK pets, says dogs catch lungworm from infected slugs and snails, often by accident while eating grass.
  • Too much grass. VCA warns that a large amount can get stuck in the stomach and may need surgery to remove.
  • Toxic plants. Some garden and house plants are poisonous. The ASPCA keeps a toxic and non-toxic plant list for dogs. It says the list isn't complete, so check the plant's name, not just the photo.

When to call your vet

Sources list these signs. Contact your vet if your dog:

  • Eats grass excessively or persistently (AKC, VCA, PDSA)
  • Vomits often, or has diarrhea, weight loss, a smaller appetite, bloody stool, lethargy or lip licking along with the grass eating (AKC)
  • Shows signs of stomach discomfort (VCA)
  • Seems unwell, or only wants to eat grass and not their usual food (PDSA)
  • May have chewed a toxic plant or swallowed too much grass (AKC)

If you think your dog has eaten something poisonous, the ASPCA says to contact your vet or ASPCA Poison Control's 24-hour line, (888) 426-4435. A consultation fee may apply.

Write down what you see

If you do call, it helps to know when this started and what came with it. A few notes turn "they eat grass sometimes" into a pattern instead of a guess. For each episode, jot down:

  • The date and time, and how long since your dog last ate
  • Where it happened, and whether the grass might have been treated
  • Roughly how much, and how eagerly
  • What followed: vomiting (and what it looked like), stool, appetite, energy, lip licking
  • Anything new that week, like a food change or a new plant at home

After a few weeks, you may see whether it clusters before breakfast, after a food change, or on certain walks. Here's what to include in a pet medical record so notes like these sit with the rest of your dog's history.

A dated Health Episode or General Note entry in the Tamadoggo pet diary app puts each episode on your dog's timeline, with up to three photos on the free plan. If family members share the walks, they can log entries too, and entries added by others show who logged them.

Sources