Most dogs eat it, and then they often throw it up. Eating grass is something of a strange phenomenon for dogs and veterinarians don’t know exactly why they do it. Dogs will eat almost anything, there’s no question about that, and their flexible pallets might explain why they eat grass; but there are other possible explanations. Of course, not all dogs will eat grass, but for those that do, cravings, dietary requirements, and illness might account for the behavior.

There is some evidence to suggest that dogs get cravings for particular kinds of foods. As such, many veterinarians believe that dogs may actually crave grass in the same way that some humans crave vegetables or snacks. Because grass was part of the natural diet for the ancestors of many dogs, it’s reasonable to expect that dogs today will still eat grass from time to time.

Moreover, dogs are omnivorous and sometimes they’ll want to make sure they get their greens. Dogs like meat and plants and while most commercial dog foods contain all the nutrients your dog needs, they’ll sometimes eat grass out of habit. Some dogs like the taste of grass and some dogs may eat it just because they’re still hungry.

Finally, many dogs eat grass when they’re feeling sick. Even dogs that normally don’t eat grass will go for it when they’re not feeling well. Usually, after eating the grass they’ll throw up. Veterinarians aren’t sure as to whether dogs throw up because they have upset stomachs or if it’s because of the grass itself. In all likelihood, it’s the illness that leads to the vomiting as healthy dogs can eat grass without throwing up. So in this case, grass may trigger vomiting as a way to rid the body of toxins.