Many dogs eat grass to varying degrees and there are many theories to explain this behavior. Scientifically, there is very little research or data.
One of the most common theories that people hear is dogs and cats eat grass to make themselves vomit when they are sick. One survey study asked pet owners to observe their pets and correlate general well-being with the action of eating grass. Very few of the pet owners (about 20%) reported that their pet was ill or vomited after eating grass.
The working hypothesis after this study is that dogs and cats eat grass as a throwback to their wild ancestors who possibly ate grass and other fibrous plants to purge their intestinal tracts and subsequently reduce their load of parasites. This behavior could also explain why, according to the previously mentioned study, young dogs tend to be more likely to eat grass than older dogs since younger dogs are naturally less resistant to parasite loads.
What to Do…
So, when asking the question of why your dog eats grass, the most likely answer is instinct. That doesn’t necessarily mean that there is nothing wrong with your pet. The behavior needs to be considered along with other factors. If your dog is vomiting consistently before or after eating grass or shows other symptoms, such as lethargy, diarrhea or abnormal stool, your dog may have an underlying medical condition and should be examined by a veterinarian. There are many causes for gastrointestinal upset. The most common reasons are parasites and dietary indiscretion although there are many other medical conditions ranging from mild to severe.
One of the easiest aspects of general healthcare for your pet is parasite prevention. The Companion Animal Parasite Council (CAPC) recommends having your dog tested for parasites at least twice yearly (four times during the first year of life). This involves microscopic examination of a fecal sample for the eggs of common parasites. In addition, many monthly heartworm and flea preventatives help reduce the risk of infection by common gastrointestinal parasites.
Although the ingestion of grass is a somewhat normal behavior for your pet, care should be taken to prevent your pet from ingesting plants that are toxic or lawns that have been treated with potential toxins. If you have a dog that likes to eat plants, it is a good idea to check your environment for potentially toxic plants and have them removed. There is also the risk of your pet picking up parasites or bacterial infections from the ingestion of plants, particularly if other pets or wildlife have access to the area. Your veterinarian can help you determine the risk factors for specific parasites in your region.