Last updated on 17/11/2020
By: Dr. Tibor Toman
Dog owners often report regarding their pet’s vomiting or diarrhea: “Trixie has an upset stomach for a few days now. She ate grass a few times when I let her out, but even that didn’t seem to help… she vomited again and her diarrhea is even worse.”.
There is also a traditional item still sold both in some pet stores and in fruit and vegetable or flower shops, called “cat grass”. This is no special plant species, just young, lush grass (or grain such as wheat), recently germinated and growing from a small flower pot, green and sweet.
There is clearly an instinct many animals have (including our pets), that probably saved lives of many during millennia, after incidentally ingesting something poisonous of foul: eating bulky, fibrous plant material, in order to irritate their stomachs to the point of vomiting up its contents. Cats (known as meticulous and passionate groomers) also do this, to get rid of hairballs – clumps of ingested hair that collects in their stomach, literally acting as a foreign body. Wild or feral cats don’t really have better and safer ways to eliminate these convolutes of hair, scientifically called “zootrichobezoars”.
Cats and dogs are not herbivores: their digestive tracts are not designed to deal with plant material like grass, leaves or twigs. Each time they (lead by instinct, curiosity, or simply, habit) ingest rough plant material, it easily causes irritation of their stomach, and vomiting. Parts that make their ways through the digestive tract, additionally upset their bowels – causing diarrhea, straining and mucousy stools.
From the veterinarian’s point of view, the other, “invisible” aspect is even more important: although people are sometimes rightfully worried about pesticides and other chemicals that could be on lawns, there are some other dangers hiding on the grass that most pet owners are not necessarily aware of: parasitic elements, soil bacteria and even some viruses. Parasites like roundworms, whipworms and hookworms successfully survived over the millennia thanks to their resistant, microscopic ova that get through the winter in the topsoil (from previous fecal contamination) and then make their ways into the digestive tract of a new host – which could be your dog, happily “grazing” on the lush grass… Soil bacteria and sometimes even viruses (like distemper and parvo) also easily get onto the grass and can cause your pet get really sick.
All in all, letting your pet to eat grass – unless you have a pet goat or some other herbivore – is not the greatest or safest thing to do.