If Your Dog Is Eating Grass, Is It Time To Take Him To the Veterinarian?

South Boston Animal Hospital blog on why dogs eat grass

No one really knows why dogs eat grass, in part because there’s been very little scientific study of this behavior in dogs. In the absence of such analysis, many theories have been floated. Some scientists believe, for example, that eating grass is a dog’s attempt to compensate for something lacking in his diet—for example, a lack of sufficient fiber, vitamins or minerals. 

Others argue that eating grass is a remnant of undomesticated dogs’ behavior, since many varieties of wild dogs have been observed eating grass.  Dogs in the wild are omnivorous, eating both meat and plant materials, for example, and domesticated dogs are simply replicating the behavior of their ancestors, according to the proponents of this theory. Still others speculate that dogs just like the taste of grass, and some believe eating grass is a dog’s attempt to induce vomiting, perhaps to remove something that’s upsetting his stomach.

Have There Been Any Scientific Studies?

If you Google, “why do dogs eat grass,” you’ll find more than 2 million results, but if you try to find scholarly articles on the subject, you’ll come up empty, or almost empty.  Stanley Cohen, Professor Emeritus in Psychology at the University of British Columbia and a prolific writer on the subject of dogs and dog psychology, attempted to find some scientific basis for the phenomenon of grass eating in dogs. He found only one relevant study:

“When I searched the scientific literature I was astonished to find that there was only one study dealing with the issue of grass eating and it was relatively recent (2008). The research was conducted at the University of California, Davis, by Karen Sueda, Benjamin Hart and Kelly Cliff and published in the journal Applied Animal Behavior Science.”

That study was designed to test the hypothesis that dogs eat grass to induce vomiting because of illness. The analysis was not especially robust, simply questioning 25 veterinary students about behaviors they had observed in their own dogs. All of the students said their dogs ate grass, none observed any sign of illness prior to their dogs eating grass, and only 8% reported seeing their dogs vomit after eating grass—hardly definitive. The researchers then expanded their sample group, first to 47 dog owners, and then online to more than 1,500 dog owners, concluding that there is no scientific basis for dogs eating grass because they are sick and want to induce vomiting. 


Do Dogs Just Eat Grass Because They Like the Taste?

Andrea Rediger, writing for the Purdue University College of Veterinary Medicine, after dismissing the idea that eating grass is an attempt to compensate for vitamin or mineral deficiencies in their diet, or to induce vomiting, suggests that dogs might eat grass just because it tastes good:

“Maybe dogs just like to eat grass. Maybe it tastes good or has a pleasing texture. Perhaps it's a compulsive behavior or something we condition with unintentional reinforcement. Who can say for sure why dogs choose to eat what they do? What makes a rotting carcass and the new sofa such delectable treats?”


Is Eating Grass Dangerous for Dogs?

There is no evidence that eating grass could be dangerous for your dog. The Purdue article does point out, however, that owners who observe a sudden increase in this behavior might want to have their veterinarian check for an underlying gastrointestinal disease. Your vet can conduct a physical exam, including fecal and blood testing, to check for inflammation or blood loss into the GI tract, or some other underlying illness. 

The bottom line is that, although no one knows with any degree of scientific certainty why dogs eat grass,  observing your dog eating grass isn’t a cause for undue alarm.  If, however, you are concerned that your dog's behavior might be a sign of some underlying illness, you might want to take him to your veterinarian to be checked out.  If you have questions about this or other issues related to your dog's health and well-being, contact us today.