Why do cats eat grass?

Direct answer: Many cats occasionally chew grass, and the behaviour can be normal even when it is followed by vomiting. The main safety questions are whether the plant is non-toxic and whether eating or vomiting has become frequent.

Not necessarily an upset stomach

Proposed explanations include normal inherited behaviour and effects on the digestive tract. Surveys suggest many cats show no sign of illness before eating plants and do not vomit every time afterwards, so “they eat grass to make themselves sick” is too simple.

The plant matters more than the theory

Many houseplants are toxic to cats, and lilies can cause life-threatening kidney injury. Outdoor grass may carry pesticides, fertilisers or parasites. If you offer cat grass, use a cat-safe species from a reliable source and keep toxic plants inaccessible.

When to ask a veterinarian

Contact a veterinarian or animal poison service promptly after possible toxic-plant exposure. Repeated vomiting, loss of appetite, drooling, weakness, diarrhoea or frequent compulsive plant eating also needs professional advice.