Veterinarians speculate that dogs eat grass for a variety of reasons, from attempting to quell nausea to reducing bloating. While dogs are unable to digest grass, the practice is largely harmless. It is relatively common for dogs to eat grass.
Dogs are not true carnivores. Rather, they are omnivores and scavengers with a preference for meat. However, they are known to eat some vegetables, fruits and berries as well as common lawn grass.
Many veterinarians point out that while grass offers no nutritional value to dogs, whose stomachs are unable to digest the plant matter, it does act as an agent to purge their digestive systems. If a dog becomes ill from ingesting pathogenic microbes, it is likely to eat grass to help flush out the microbes. Dogs often vomit after eating a significant amount of grass.
Some dogs nibble on small amounts of grass daily, while others only partake now and again. Although there is little research on the behavior, veterinarians tell dog owners not to worry unless their dogs are throwing up most of their meals. They also caution pet owners to make sure their dogs do not eat poison plants or grass that has been sprayed with weed killer while they are grazing.