Why does my dog keep eating grass and vomiting?

Eating grass can be a sign that your pup isn't feeling well- he thinks that it will aid his digestion. You might want to try another food (he might have an intolerance or allergy to something in his current food). It might also be a sign of a blockage in his stomach. If you have a yard and let him run free there is not much you can do to stop him other than physically watching him while he is outside and stepping in when he starts "grazing". On walks, keep a quick pace so he doesn't have time to eat, and move along when he starts munching.