Why does your dog eat grass?

The Case

Morning walk. Everything normal.

Then your dog stops, lowers its head, and starts grazing like a small, determined cow.

You pull the leash. It chews faster.

Sometimes it throws up twenty minutes later. Usually it doesn't.

Either way, tomorrow it does it again.

Your Theory?

Here's the evidence.

Your dog eats a complete diet.

It looks perfectly happy while it chews.

It seems picky about it, going for fresh, young blades rather than any old patch.

And the vomiting, when it happens, is the exception.

The internet's verdict: "upset stomach, self-medicating."

Does the evidence agree?

The Reveal

Mostly, no.

Researchers at the University of California, Davis surveyed owners of dogs that regularly eat plants. Grass was by far the most common choice. Fewer than one in ten of those dogs seemed ill beforehand, and only about a quarter were ever seen vomiting afterwards.

So the sick-dog theory doesn't fit most cases. A dog that feels fine eats grass, and usually keeps it down.

What does fit? Ancestry. Grass turns up regularly in wild wolf droppings, and one leading idea is that wild canids grazed routinely, possibly to help push intestinal parasites through. Your dog may have inherited the habit, even if it no longer needs the reason.

There's also the simplest explanation: some dogs just seem to like it. Fresh grass is soft, juicy, and right there.

Case Closed

For most dogs, this case closes with no charges filed.

Case closed. Let it graze.