There is a school of thought that they do it to calm an upset tummy. My dogs throw up. I know that if I throw up it does calm my stomach for a while. Dogs can’t digest grass. They lack the enzyme to digest it.
In reality these dogs often may have an inflammatory disease such as gastric reflux. or inflammatory bowel disease, something to mention at your next visit. Our little guy will retch and throw up yellow, foamy liquid, usually (I think) in the house. This can be caused by diet or allergies. Less than 25% actually throw up.
Why your dog might be eating grass includes improving digestion, treating intestinal worms, or fulfilling some unmet nutritional need, The second most often reason given is that dogs evolved from wild wolves. Wolves and wild dogs eat their prey, which are grass eaters. They eat pretty much the whole animal including the innards. It is usually suggested that there something in canine physiology that is satisfied by the nutrients by the nutrients that may be in the grass. Perhaps the roughage is needed in the dog’s diet.
There has been only one study in 2008 on why dogs eat grass. A number of surveys showed that most dogs eat grass and that only a small percentage throw it up. It was reported that none of the dogs in this study showed any signs of illness. It was also noted that dogs who appeared ill before eating grass were the dogs most likely to vomit after.
Then there are the dogs that just enjoy eating grass and don’t have any ill effects. Or they are bored and need some interaction with you. Playing catch, or like my dogs, playing keep away, will take their minds of it. If it bothers you.
Most experts don’t think the action is dangerous unless there’s pesticide or other chemicals on your lawn or in your garden. Also, there are plants that are toxic for dogs.
Aloe Vera, Amaryllis, Baby’s breath ( we had a cat who would anything to get to the Baby’s Breath in any bouquet) , Azalea’s, Rhodedendron, Begonia, Castor Bean, Carnations. Chrysanthemum. Daffodils, Cyclamen, Lillies, Hosta, Milkweed, Gladiola, Ivy, Oleander, Pathos, Tomato plant, Tulips and Yew. We have grown many of these plants and have been very fortunate that our dogs don’t like any of them.
Then there food that is toxic: Alcohol, Avocado Cooked Bones, Candy and chewing gum, Citrus oil extracts, Fish, Hops, Milk and dairy products (Although yogurt in treats is common and good), Rhubarb, and tomato leaves , String, Sugar, Mushrooms, Human vitamins, AND even more dangerous foods – Chocolate, Coffee, Corn on the cob, Grapes and raisins, Macadamia nuts, Onions and chives, Tobacco, Xylitol, Yeast (on its own or in dough)
Call your vet or emergency clinic immediately if problems arise.