Pet Care Advice 》 Why does My Cat Eat Grass?

You may have noticed your cat eating grass outside, despite eating their usual food. This shouldn’t be a cause for concern, as eating grass is an instinct which their digestive system is accustomed to. There is no firm evidence on why they do it, but here are some of the theories!

To help with digestion

Grass is a source of fibre, which can bulk up stools and help them pass through, preventing diarrhoea or constipation. 

To make themselves vomit

Eating grass can stimulate the vomiting reflex; the way this happens is not understood but may be because grass is rough or because cats lack the enzymes to digest it. Some think that cats therefore eat grass to help purge their stomachs of other indigestible things they've eaten – fur, feathers, bones.

To break down fur balls

As cats groom themselves regularly using their tongues, they inevitably ingest a lot of hair. As a result, furballs form in the stomach, which are often vomited up. However, some fur passes further down the digestive tract, and some think that grass can break furballs up and help them pass.

To supplement their diet

As well as fibre, grass contains B vitamins.

Health Risks

There are some risks associated with grass eating. You should take particular care to differentiate between potentially poisonous plants and normal grass.

You should be vigilant of any areas your cat may roam in that contain:

  • Lilies
  • Chrysanthemums
  • Daffodils and bulb plants
  • Rhododendrons
  • Ivy
  • Onion plants
  • Potato plants

This is not a comprehensive list of poisonous plants – there are many others. Please check your house, garden and neighbourhood plants against the following websites:


Additionally, any areas of grass that have been treated with fertilisers and other chemicals should be avoided to prevent ingestion of toxins.

If you are concerned about your cat's grass-eating habits, or you think s/he may be eating too much grass, please contact your veterinarian for advice so that they can check for any underlying health problems.