Why do dogs and cats eat grass?

“Why does my dog eat grass?” “My cat loves to chew on the leaves of my plants. Why does he do that?” These are questions that several readers have asked me in one form or another. So, I’m going to try to answer them for you.

Why do Dogs and Cats Eat Grass?

Unfortunately, the short answer to that question is that we do not really know. There are lots of theories. Some of the most common are:

• dogs and cats eat grass because they have an upset stomach or intestinal tract and need to make themselves vomit
• dogs and cats eat grass because they have a dietary deficiency
• dogs and cats eat grass because it helps them purge intestinal parasites from their gastrointestinal tract

Do Dogs and Cats Eat Grass Because They are Sick?

Dr. Karen Sueda, Dr. Kelly Cliff and Dr. Benjamin Hart have completed several surveys which seek to examine this question. (Source: “Why do dogs and cats eat grass?”, Dr. Benjamin Hart,FIRSTLINE, December 1, 2009). Let’s look more closely.

According to the surveys, roughly two out every three pet owners said their dogs eat plants daily or weekly. Grass is apparently the most common plant which dogs eat. Other surveys have indicated that cats may ingest plants other than grass more frequently but eating grass does not seem to be as common in cats as in dogs. So, it would appear that the majority of dogs eat grass on a regular basis and cats also sometimes engage in this behavior but may prefer other plant varieties.

Very few dog owners (8% in one large survey conducted online) said that their dog frequently appeared to be sick before eating grass. So, even though illness may be responsible for the habit in a few dogs, it does not appear that disease is the cause for most grass-eating dogs. The same appears to be true in cats.

Is it Normal for My Dog or Cat to Vomit After Eating Grass?

Nearly 1/4 of dog owners said their dog vomits after eating grass. Preliminary data in cats indicates that they also vomit only occasionally after eating grass. So, in answer to the question, vomiting can occur after a pet eats grass but does not always occur.

Younger Dogs Eat Grass More Frequently Than Older Dogs

According to the online survey, which also gathered data on the age, sex, sexual status (intact vs. neutered) and breed, younger dogs were found to ingest grass more often than more mature dogs. Younger dogs were also less likely to appear sick prior to eating grass or to vomit afterwards. Similar data, to my knowledge, is not yet available for cats.

It is suggested that this age discrepancy may provide proof of the fact that dogs (and possibly cats) eat grass as a means of purging worms and other parasites from their gastrointestinal tract. The theory put forth by Dr. Hart and his group is that “the plant material passes through the intestinal tract, increasing intestinal motility and wrapping around worms and thereby purging the tract of intestinal nematodes”. (Nematodes are a type of worm.) Further support for this theory is the fact that young puppies and kittens tend to be infected more heavily with worms than older animals, which usually develop some amount of immunity. Thus, young puppies (and maybe young kittens) may be more likely to eat grass because it serves a biological purpose (i.e. it gets rid of some of the worms).

I do not think we have clear-cut proof at this point in time that dogs and cats eat grass to purge themselves of intestinal parasites. However, it is an interesting theory and may very well have some merit. Further research is needed, however, before we can say that we know definitively why dogs and cats eat grass.

Should You Worry if Your Dog or Cat Eats Grass and Vomits?

In my veterinary practice, large numbers of dog owners ask about their dog and its grass eating behavior. I hear these questions less often from cat owners but do hear them occasionally. Most of these dogs and cats do not appear ill on examination. Dog owners often ask whether its okay if their dog vomits after eating grass, but I don’t have any statistics as to how many of my client’s dogs vomit after eating grass versus not vomiting. Based on the number of people of asking, I assume it to be a fairly high number so I was a little surprised to read in the survey results that a little less than one quarter of the dogs that eat grass vomited afterward.

My advice: I would not worry if your dog or cat eats grass as long as your he/she is feeling well and is not acting sick. The vomiting which occurs after eating grass should be transient. If your pet continues vomiting, I would advise contacting your veterinarian. Of course, if your pet is acting sick in any other way, you also need to contact your veterinarian.

Needless to say, if you are going to allow your pet to eat grass, the grass should not be treated with chemicals or fertilizers.

Other types of plants are another story completely. These concern me, as a veterinarian, because so many of them can be toxic and can poison a pet. I advise caution in letting your pet chew on or ingest plants. Both house plants and those in the garden can be toxic species. Even the least toxic of these plants can cause vomiting, but some of them can cause life-threatening symptoms. The most toxic of these plants can be fatal, even in small quantities.

These poisonous plants do not, of course, include plants such as cat nip and cat grass. Cat nip and cat grass are safe for almost all cats.

What About Your Dog or Cat? Does Your Dog or Cat Eat Grass? Eat Other Plants? Vomit Afterwards?

Please share your experiences with the other readers by posting a comment below. Does your dog eat grass? How often? Does he/she seem sick beforehand? Does he/she vomit afterward?

What about you cat owners? Does your cat like grass? Does he/she chew on your house or garden plants? Do you think he/she does it because of illness? Does your cat generally vomit afterwards?

I’ll share my experiences. Of my 5 cats, two of them will chew on plants if I allow it. I try very hard to keep house plants out of their reach and they do not go outdoors, so they have no access to grass. However, all five of them LOVE catnip, which, of course, is a type of herb.

Please don’t forget to tell about your pet. Scroll down to the comment box or comments link to post a reply.

Photo Credit: didbygraham/Flickr.com

This entry was posted on Tuesday, January 19th, 2010 at 4:00 pm and is filed under Canine Nutrition, Cat Behavior and Training, Cat Diseases, Cats, Dog Care, Dog Training and Behavior, Dogs, Features, Feline Nutrition. You can follow any responses to this entry through the RSS 2.0 You can leave a response, or trackback from your own site.