Why Do Cats Eat Grass?
Quick answer
Cats eat grass mainly for the fiber it provides and because it is a natural instinct, not because they are sick.
The full answer
The behavior is common and usually harmless. Experts still debate the exact reason, but the leading theories are that plant fiber helps move swallowed hair and food through the digestive tract, that it can trigger vomiting to bring up hairballs, and that it may supply small amounts of nutrients such as folic acid. Some cats simply enjoy the taste and texture, or eat grass out of boredom.
If your cat nibbles grass, make sure it is safe. Never let it graze on lawns treated with pesticides, herbicides, or fertilizer, and keep toxic houseplants such as lilies, azaleas, and oleander well out of reach. Growing a pot of cat grass indoors, usually oat, wheat, or barley, is the safest option and gives your cat a clean, pesticide-free source.
Occasional grass eating with no other signs is not a concern and needs no treatment. However, if your cat eats grass constantly, vomits frequently, has diarrhea, loses weight, or seems lethargic, the grass may be pointing to an underlying stomach or intestinal problem. In that case, and especially if you suspect your cat ate a toxic plant, contact your veterinarian right away.