Why Do Dogs Eat Grass? What the Research Actually Says

Dogs eat grass for several reasons including instinctive grazing behavior, fiber supplementation and in some cases nausea relief, but contrary to popular belief, grass eating is rarely a sign of illness. A peer-reviewed study found that 68 percent of dogs eat plants daily or weekly, yet only 9 percent showed signs of being ill before eating grass, and fewer than a quarter vomited afterward.

The behavior is normal for most dogs and does not require intervention unless it becomes sudden, compulsive, or accompanied by other symptoms.

How Common Is Grass Eating in Dogs?

Grass eating is one of the most frequently reported unusual behaviors in domestic dogs, and it is far more common than most owners realize. A 2008 study by Sueda, Hart and Cliff published in Applied Animal Behaviour Science surveyed owners of 1,571 dogs and found that 68 percent reported their dogs ate plants on a daily or weekly basis. Across all plant-eating dogs, grass was by far the most commonly consumed plant type.

Importantly, the study found no meaningful correlation between grass eating and subsequent vomiting. Only 22 percent of dogs that ate grass vomited afterward, and only 9 percent of dogs showed signs of illness before eating grass. These findings challenge the deeply held folk belief that dogs eat grass specifically to induce vomiting when they feel sick.

Reason 1: Instinct From Wild Ancestors

One of the strongest evolutionary explanations is that grass consumption serves as a behavioral remnant from wolves' and wild canids' ancestors. Regular consumption of the stomach contents from herbivore prey by wolves and other wild canids included pre-digested plant material and grass. These contents provided fiber, micronutrients and potentially beneficial gut bacteria that came from the prey's digestive tract.

Domestic dogs descended from wolves retain many ancestral behavioral tendencies, particularly around feeding. From this perspective, grass nibbling is no different from the instinct to bury food, circle before lying down, or sniff intensively before eating, behaviors with clear ancestral function even when the original context no longer applies.

Reason 2: Fiber Supplementation

Many veterinary nutritionists believe that grass eating is a self-regulatory behavior through which dogs supplement dietary fiber. Dogs on low-fiber diets appear to eat grass more frequently than those on high-fiber diets, and some dogs reduce their grass consumption when transitioned to diets with higher fiber content.

Fiber influences gastrointestinal motility, promotes healthy stool formation and supports populations of beneficial gut bacteria. Dogs that consistently eat grass despite having access to it may benefit from a dietary fiber increase through vegetables, legumes, or a high-fiber commercial food formulation.

Notably, the relationship between grass eating and diet is not universal, many dogs on high-quality, high-fiber diets still eat grass regularly, suggesting that dietary supplementation is one of several motivations operating simultaneously.

Reason 3: Nausea Relief and Vomiting Induction

Although the Sueda study showed that vomiting after grass eating is less common than popularly believed, a subset of dogs do appear to use grass strategically when nauseous. The distinction may relate to how the grass is consumed: dogs that gulp large quantities rapidly and repeatedly swallow without chewing may be attempting to trigger the gag reflex, while dogs that leisurely graze and chew individual blades appear to be grazing without any illness motive.

Some research suggests that certain grass compounds have gastroprotective properties. Wheatgrass in particular contains chlorophyll, antioxidants and trace minerals that have demonstrated anti-inflammatory and antacid properties in laboratory settings, though direct evidence in dogs remains limited.

If a dog that rarely eats grass suddenly begins consuming large amounts and regularly vomits afterward, this pattern warrants veterinary evaluation to rule out underlying gastrointestinal conditions including inflammatory bowel disease, gastric reflux, or foreign body obstruction.

Reason 4: Boredom and Grazing Behavior

When dogs lack enrichment or engagement outdoors over long periods, they can develop habitual grazing behaviors with no medical or nutritional rationale. The repetitive oral motion of grazing serves as self-soothing for some dogs in the same way that some dogs chew non-food items when stimulation levels are low.

Dogs whose owners boost exercise, play and training routines frequently report that habitual grass eating decreases. Suitable chew toys, puzzle feeders and social time give dogs alternative outlets for their oral and exploratory drives.

This boredom-related grazing is more common in energetic breeds with high cognitive needs, Border Collies, Jack Russell Terriers, Australian Shepherds, that become restless when under-stimulated.

Reason 5: It Simply Tastes Good

Dogs have taste preferences, and many simply find certain grasses and plants palatable. Young, tender grass blades have a mild sweetness from chlorophyll and simple sugars that some dogs find appealing. Dogs commonly graze selectively, preferring certain grass species and ignoring others, behavior inconsistent with a strictly medicinal motivation.

Observations across seasons back this pattern: owners report their dogs eat more grass in spring when new growth is particularly tender and flavorful, and less in late summer when grass turns tough and bitter.

When to Be Concerned About Grass Eating

Grass Eating Pattern	Likely Cause	Action Needed
Occasional nibbling of grass blades	Normal grazing / instinct	None required
Frequent grazing during walks	Fiber seeking / habit	Consider high-fiber diet
Gulping large amounts rapidly	Possible nausea	Monitor; vet if persistent
Frequent vomiting after grass eating	Gastrointestinal issue	Veterinary evaluation
Sudden onset of heavy grass eating	Dietary change, illness, stress	Veterinary evaluation
Eating non-grass plants including toxic species	PICA / behavioral	Prevent access; vet consult
Accompanied by weight loss, appetite change	Underlying disease	Urgent veterinary evaluation

Grass Eating vs. Eating Other Plants (PICA)

PICA involves the compulsive eating of non-food items. Occasional grass eating is normal, but consuming soil, rocks, fabric, wood or other plant material compulsively may signal PICA. This behavior can result from nutritional deficiencies, gastrointestinal disease, neurological conditions or anxiety disorders.

Of particular concern is consumption of ornamental and garden plants, many of which are toxic to dogs. The ASPCA Animal Poison Control Center maintains a list of plants toxic to dogs, including common garden species such as azalea, rhododendron, sago palm, oleander and foxglove.

Does Grass Carry Risks for Dogs?

Dogs can safely eat grass on its own. Grass treated with pesticides, herbicides or fertilizers introduces real risk, though. Vomiting, neurological effects and organ damage have occurred from chemical exposures on treated lawns, though the specific compound and amount consumed determine the pattern of toxicity.

Dogs that graze in areas that may have been treated should be observed after returning indoors. Signs of pesticide or herbicide toxicity include excessive salivation, vomiting, diarrhea, muscle tremors, or lethargy. If any of these signs appear following grass eating, veterinary care should be sought promptly and the owner should bring information about any chemicals recently applied to the lawn.

Intestinal parasites including roundworms, hookworms and whipworms spread through contaminated soil and can be ingested when dogs eat grass. Regular grazers should follow a veterinarian-prescribed parasite prevention protocol.

Common Plants Dogs Eat and Their Safety

Plant	Toxicity to Dogs	Notes
Lawn grass (most species)	Non-toxic	Safe unless treated with chemicals
Wheatgrass / oat grass	Non-toxic	Sometimes grown indoors as dog treat
Dandelion	Non-toxic	Mild diuretic; occasional eating safe
Clover	Generally non-toxic	Large quantities may cause bloating
Buttercup	Mildly toxic	GI irritant; avoid access
Foxglove	Highly toxic	Cardiac glycosides; emergency
Sago Palm	Extremely toxic	Liver failure; fatal in small amounts
Azalea / Rhododendron	Highly toxic	Cardiac and neurological effects

What to Do If Your Dog Eats a Lot of Grass

For dogs that graze occasionally without vomiting or illness signs, no intervention is necessary beyond ensuring the grass is pesticide-free and maintaining routine parasite prevention. For dogs that seem compelled to eat grass, especially if vomiting follows, a trial of high-fiber diet supplementation is a reasonable first step.

Adding vegetables such as pumpkin, green beans, or carrots to the diet increases fiber intake in a controlled way. Some veterinarians recommend cat grass or wheatgrass grown indoors as a safe, pesticide-free alternative for dogs that graze habitually.

For further reading on related dog behavior and health topics, see Signs of a Healthy Dog, Why Do Dogs Lick People?, How Long Do Dogs Live?, How to Train a Puppy and Why Do Dogs Howl?.