Does your dog eat grass? Many dog owners report that their dogs participate in this puzzling behavior.

Grass eating seems to fall into one of two scenarios:

Scenario 1:

Your dog is licking his lips and swallowing. He frantically asks to go outside. You open the door, and he bolts for the yard and gulps down a few mouthfuls of grass. In a few moments, he throws up.

Scenario 2:

You take your dog out for his afternoon potty break. He may or may not do his business, then he wanders over to a favorite patch of grass, perhaps growing by the fence. He carefully peruses the grass blade by blade, as though he were picking out delicacies at a buffet line. "Hmm. . . maybe; no, not this one; perhaps over here. . . " Then, as though he's found the perfect blade, he slowly nibbles at the grass with his short front teeth. More often than not, your dog does not vomit after eating this grass.

So why do dogs eat grass?

There's a fair amount of anecdotal evidence to suggest that sometimes dogs eat grass when they have a tummy ache or some other digestive issue and they need to clear their stomach. This aligns with the behavior observed in Scenario #1. Some professionals doubt that dogs have the ability to self-diagnose themselves in this way, but it happens often enough and with such consistency that it's hard to completely discount the theory. But what about the dogs that fall under Scenario #2? The ones that seem to feel fine, eat a bit of grass, and suffer no ill effects. What's that all about? No one knows for sure. Unlike cats, which are almost strictly carnivores, dogs are omnivores. They not only can and will eat most anything, they actually need more than just meat in their diets. Dogs' ancient ancestors typically ate every part of an animal when they made a kill. Many of the animals they hunted were herbivores. When they consumed the stomach and other parts of the digestive tract of these animals, the ancient canines would have ingested plant material as well. Some believe that dogs eat grass because they're missing something in their diet that the grass supplies, such as fiber. Others argue that dogs' stomachs do not contain the enzymes to properly break down grass, so they gain no nutritional value from it. Another thought is that dogs just like the flavor or texture of eating grass—so your dog may be munching on grass just because he wants to. That theory seems to be supported by the care many dogs take in finding the perfect piece of grass.

If in doubt, always go to the vet.

Although there are many different ideas on why dogs eat grass, people seem to agree that eating grass occasionally will not harm your dog. If you notice that your dog eats grass regularly, it may be a good idea to take him to the vet to make sure there's not an underlying problem. One note of caution, though: although the grass itself isn't harmful, pesticides, herbicides, fertilizers, and other chemicals used to treat lawns can be poisonous to your dog. Make sure the grass your dog eats hasn't been treated with any chemicals. If you can't be sure, don't allow your dog to eat that grass. Otherwise, unless he starts to graze like a cow, let him enjoy the occasional piece of grass. After all, even if you're feeding him the best food, your dog still likes a little variety in his diet every now and then.