Why does my dog eat grass?

Grass eating is one of the most common behaviours dog owners ask about — and despite the widespread belief that dogs eat grass to make themselves sick, the science tells a more nuanced story.

Is grass eating normal?

Yes, absolutely. Studies have found that approximately 79% of dogs eat plants regularly, making it one of the most common behaviours in the species. In most cases, it is completely harmless.

Why dogs actually eat grass

1. It tastes good / they simply like it — the most boring and probably most accurate explanation. Dogs are opportunistic omnivores with a wide variety of natural tastes. Fresh spring grass in particular is sweet and appealing.

2. Instinctive fibre supplementation — wild canids (wolves, coyotes) regularly consume plant material. Grass may provide insoluble fibre that helps move things through the gut, or aid in passing intestinal parasites.

3. To settle an upset stomach — some dogs do appear to eat grass specifically when they feel nauseous, and some subsequently vomit. However, research shows that less than 25% of dogs who eat grass vomit afterwards — so this is far from a universal rule.

4. Boredom or anxiety — dogs that are under-stimulated or stressed sometimes graze repetitively. This is more compulsive than occasional grass eating and often happens alongside other repetitive behaviours.

5. Nutritional deficiency — rare, but a sudden increase in plant eating can sometimes indicate a deficiency in fibre or certain micronutrients. This is worth mentioning to your vet if it is a new behaviour.

When to be concerned

- If your dog eats grass frantically, in large quantities, and always vomits — this suggests they are using it to relieve significant nausea. Investigate the underlying cause.
- If the grass eating is new and obsessive — rule out a gastrointestinal problem or anxiety.
- Pesticide and herbicide risk — the main practical danger. If your dog grazes on grass treated with lawn chemicals, fertilisers, or slug pellets (metaldehyde is extremely dangerous), this is a serious toxicity risk. Keep your dog away from treated areas for at least 48 hours after application.

Should you stop it?

Occasional, calm grass eating on untreated lawns is nothing to intervene on. Compulsive, frantic, or vomit-inducing grass eating warrants investigation.