Why does a cat eat grass?

Cats do eat grass occasionally, but not because of disease, but because it is a habit that has evolved in them.
They conducted an online survey of more than a thousand people who not only raised cats but also observed their cats' habits and movements for at least three hours a day. The survey found that the vast majority of domestic cats ate grass at least six times in their lifetime. There were very few cats that did not eat grass even once in their lives.
Survey participants revealed that all grass-eating cats were found to be perfectly healthy, but most of them vomited after eating grass, indicating that they were adversely affected by eating grass.

So why does a cat eat grass? Answering this question, Dr. Hart says that the evolutionary ancestors of modern cats lived in forests about five million years ago, where they were exposed to stomach parasites (stomach worms) like other wild animals. We know about the first catsAlthough she was a carnivore, she occasionally ate grass to get rid of stomach worms, which helped her stomach muscles work better and easily expelled fecal parasites as well as stomach parasites. Used to be

As far as cat rearing is concerned, the history of this process is about 8000 years old, while this period is very short for the change in the natural habit (instinct) created as a result of evolution. Pet cats don't usually have stomach worms, but they do occasionally crawl on grass because of their evolutionary instincts, even if they vomit after eating it.
That is, it can be said that cats do not eat grass because they are sick, but because they want to be safe from getting sick.