Why cats eat grass: a study of thousands of owners upends the hairball explanation
Published by Planète Pets · managing editor: Clément Lacaille · how our guides are written
Two surveys of cat owners run over roughly a decade, published in 2021 by Hart and colleagues in the journal Animals, gathered between 1,000 and 2,000 responses each on cats' plant-eating habits (see the study, doi 10.3390/ani11071853). Our other food guidance is gathered in the cat food section.
Contents · 5 sections
An ordinary behaviour, not a sign of illness
About 65% of owners in the first survey had seen their cat eat plants at least once a week, and only 11% of cats had never been seen doing it. Crucially, very few cats showed signs of feeling unwell before eating plants (6 to 9%, depending on the survey): for the vast majority, this is a spontaneous behaviour rather than a response to pre-existing digestive discomfort.
The hairball link called into question
The most common explanation — eating grass to expel hairballs — does not fully hold up: short-haired cats eat plants just as often as long-haired cats, even though the latter objectively swallow more hair while grooming. Between 27 and 37% of cats vomit frequently after eating plants across the two surveys, but that figure does not explain why cats at low risk of hairballs keep the behaviour at the same rate. Our article on preventing hairballs covers what actually helps on that specific point — brushing and diet, more than cat grass.
A detail that depends on age
Young cats eat plants more often than older cats, and vomit less frequently afterward — a pattern that suggests an exploratory or ancestral feeding behaviour rather than a simple corrective reflex. This ties in with what we already know about the differences between cat grass and catnip, two plants with quite distinct uses.
What this means in practice
Offering indoor-grown cat grass remains good practice — it reduces nibbling on potentially toxic houseplants — but there is no need to worry if a cat never touches it, nor to present it as a treatment against hairballs.
Frequently asked questions
My cat vomits after eating grass, is that serious?
According to this study, occasional vomiting after eating plants is common and generally not serious; repeated vomiting outside that context warrants a vet visit.
Should I force a cat to eat grass?
No: leaving it available is enough, the cat will turn to it on its own, at its own pace. Find all our guides on the cat hub.
An accessory from our shop for this use: Raised-edge silicone feeding mat for cats (€25.90) · the whole shop
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This guide is part of Planète Pets’s Cats universe. Our advice is general in nature: for any health concern, your veterinarian remains the only reference.
