And should I try to prevent it?
IANAV*, but I think it’s an instinct for a dog with an upset stomach, as eating grass helps them throw up.
*V=Veteranarian
Yep, thats what I heard too. Dont know if its true though
I always heard that as well. I grew up with many dogs, and never saw it happen, tho my mother always said that was why they did it. Sure, I saw plenty of sogs throw up, but I cannot remember it being in associated with eating grass.
Now I have my own dog (a ridgeback, Ellie), and she eats grass a few times a day when I take her for a walk. She vomits maybe once a month.
So, I think it’s an old wives tale.
a
I heard it had something to do with needing undigestable fiber in their system for some reason. However, I don’t know if it’s true.
I’ve seen cats do this as well.
Is it a form of pica? My dog does it once in a while, but he can get on rolls where he does it daily for a week and then not do it for a couple of months.
If it has to do with upset stomachs, then my cats are really sick. I have two that go out with me every day to munch a little fiber. I have a very hard time believing they are in a constant state of nausea.
Besides, of all my five cats, those two throw up the least.
Yeah, I’ve never seen my dog vomit after eating grass, and he eats some almost every day. I had heard that explanation before, but I don’t think that’s the reason in his case.
Sometimes, it may be because of a slight vitamin deficiency. Dogs in the wild are not purely meat-eaters. They munch on the stomachs of their herbivore prey, thus injesting the partially-digested vegetable matter, and they also take a bite or two of various plants they find in the wild.
There’s a product called Barley Dog which you can fin din most pet stores. One of my dogs stopped eating grass entirely when I started putting this on her food.
If your dog is eating grass because she has a upset stomach, you can also get brewer’s yeast tablets at the pet store. Give them a tablet once a day, and it takes care of most problems.
Also, take a good hard look at the food you’re feeding your dog. Cheap dog food, like the kind you get at the grocery store, often has low-vitamin content and lots of nasty chemicals (including traces of BHG). Switching your dog’s food to a better quality might solve the problem.
Alternately, you can add things from your own kitchen to your dog’s food to supplement their diets. For example, if you’re putting spinach in a casserole, put half a cup of the lefttover spinach in their food. You can give them just about any cooked vegetable. (Unsalted and unbuttered, of course. Though, as an FYI, cabbage will make them fart, though, so you might want to hold off on that.) Many dogs like raw carrots-- some owners actually buy bags of baby carrots to give as treats.
Really? I just thought my dog was weird. It was funny to see her grasp the carrot between two paws and gnaw on it 
Nearly every time I saw her eat grass I’d later find puke-covered grass later on, so whatever reason she ate it for didn’t result in much of it staying in her belly.