Why do dogs eat grass?

Dogs eat grass for reasons researchers have not fully pinned down, but it is very common and generally considered normal dog behavior. In a large owner survey, most plant-eating dogs rarely seemed sick before or after, so watch for a sudden change in the habit and what is on the grass.

How common is grass eating in dogs?

Grass eating is very common in dogs. In a study from a veterinary teaching hospital, 79% of 47 owners whose dogs had daily access to plants said their dog had eaten grass or other plants.¹

The same researchers then ran an internet survey of owners of plant-eating dogs and analyzed 1,571 responses. Overall, 68% of those dogs ate plants daily or weekly, and grass was the plant owners saw their dog eat most often.¹

Is it normal for dogs to eat grass?

Yes, eating grass is normal for most dogs. The study's authors concluded that "plant eating is a normal behaviour of domestic dogs."¹

Sex, reproductive status, breed group and diet type showed no clear link to how often dogs ate plants. Younger dogs ate plants more often than older dogs.¹

A University of Wisconsin-Madison School of Veterinary Medicine article agrees: if your dog commonly eats grass, it is not an immediate cause for alarm.²

Do dogs eat grass to make themselves throw up?

Most dogs probably do not eat grass to make themselves throw up. In the survey, only 9% of dogs were reported to frequently seem ill before eating plants, and only 22% to frequently vomit afterward.¹

Nausea may be a reason some dogs eat grass, but not always, according to the University of Wisconsin-Madison article.² Cornell's Riney Canine Health Center describes infrequent vomiting, such as after eating grass, as likely an isolated incident.³

What are the main reasons dogs eat grass?

The exact reason dogs eat grass is not clearly known.² Veterinary sources point to 3 explanations:

• Normal scavenging: dogs are scavengers, and trying unusual things is common for them.²
• An inherited habit: the survey authors suggested plant eating may reflect a predisposition passed down from wild canid ancestors, possibly as a way to expel intestinal parasites. They noted that controlled studies could test this idea.¹
• An upset stomach, sometimes: nausea may play a part for some dogs, though few grass eaters are reported to frequently seem ill first.^1,2

When should you call your vet about grass eating?

Call your vet when grass eating is new for your dog or comes with other changes. A clinical instructor at UW-Madison put it this way: "If it's a new behavior, it may indicate a change in your dog's health." Look for other changes in behavior or daily habits, including any recent change in diet.²

Vomiting is the other thing to watch. Cornell's Riney Canine Health Center advises contacting your vet if you see:³

• Blood in the vomit, or material that looks like coffee grounds
• Lethargy
• Vomiting that lasts more than 24 hours
• A painful belly or a fever

Cornell also notes that vomiting as often as once a week may indicate a disease, so a regular pattern is worth a vet visit.³

Are lawn chemicals dangerous if my dog eats grass?

Some lawn chemicals are dangerous to dogs, so it pays to know what has been applied. A UW-Madison veterinary article explains that fertilizers are spread in dilute amounts but can cause vomiting and bloating if a dog eats a large quantity. Most herbicides and fungicides are heavily diluted too, and the most likely problem if a dog eats them is vomiting.⁴

Pesticides are the bigger concern. The same article says pesticides are generally toxic to pets, and insecticides affect the nervous system of dogs and need immediate veterinary care.⁴

A few habits lower the risk:

• Keep your dog off treated areas until the lawn has been thoroughly watered and allowed to fully dry.⁵
• If you use a lawn care service, tell them you have pets.⁵
• Use pet-safe lawn and garden products when possible.⁵
• Store all lawn and garden products out of reach or locked away.⁴

Which plants should dogs not eat?

Some plants and fungi around the home can be toxic. Texas A&M's College of Veterinary Medicine lists sago palms and rose laurel among non-garden toxic plants to watch for, and advises keeping pets away from mushrooms and compost piles.⁵

The same source suggests using a phone app to identify the plants in your yard, supervising pets outside, and not letting them drink from ponds or standing water, where blue-green algae can grow.⁵

What should you do if your dog eats something toxic?

If your dog eats something toxic, act right away. Texas A&M advises removing your pet from the source, then calling your veterinarian, an emergency veterinary hospital or a pet poison helpline immediately. Do not try to treat your dog at home unless a veterinarian tells you to.⁵

Bring the plant sample or product label if you can.⁵ If it was a lawn or garden product, take a photo of the packaging so you can tell a poison center the active ingredient.⁴

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