The short answer: eating grass is one of the most common things dogs do on a walk, and most of the time it is completely normal. Studies suggest that up to 80 percent of dogs eat grass or other plants at some point. Fewer than 25 percent vomit afterwards, which means most dogs are not eating grass because they feel sick — they just seem to want it.
If your dog grazes on a few blades during a walk, carries on happily, and shows no signs of illness, there is very likely nothing wrong.
Why they do it
Researchers do not have a single confirmed answer, but several explanations hold up well.
Instinct. Dogs descend from wolves and other wild canids that ate whole prey — including the plant matter in their prey’s stomach. Eating vegetation appears to be an inherited behaviour that stuck around long after dogs moved onto kibble.
Fibre. Grass is mostly indigestible fibre. Some dogs seem to seek it out when their diet is lower in fibre than their gut would like. Anecdotally, dogs fed higher-fibre diets sometimes eat less grass, though this has not been studied rigorously.
Taste and texture. Some dogs simply enjoy the taste of fresh grass, especially young spring shoots. This is not very different from a dog that likes to chew sticks or roll in leaves — it is part of being a dog outdoors.
Stomach upset (sometimes). A smaller number of dogs do eat grass rapidly and in large amounts when they feel nauseous, and they often vomit shortly after. This pattern — frantic gulping of grass followed by vomiting — looks different from relaxed, selective grazing and is more likely to signal genuine discomfort.
When to step in
Occasional grazing is harmless, but a few situations deserve attention:
- Treated lawns. Grass sprayed with herbicides, pesticides, or fertilisers can make a dog sick. If you do not know whether a lawn has been treated, keep your dog off it. Public parks and verges are the most common exposure points.
- Sudden increase. A dog that never cared about grass and now eats it at every opportunity may be responding to a dietary gap or a digestive issue. A vet check is reasonable.
- Vomiting every time. If your dog eats grass and vomits consistently, the grass itself is not the main concern — the recurring nausea is. Mention it at the next vet visit.
- Slugs and parasites. In some regions, lungworm can be transmitted through slugs and snails that sit on grass. If lungworm is a known risk in your area, discourage grass eating outdoors and keep up with regular parasite prevention.
What you do not need to do
You do not need to stop a dog from eating a few blades of clean grass on a walk. Pulling the lead away every time a dog nibbles grass can create tension on the walk and remove a behaviour that the dog finds satisfying. Unless the grass is treated or the dog is eating compulsively, relaxing about it is the better call.
If you want to reduce grass eating, adding a small amount of steamed vegetables — green beans, broccoli, or spinach — to the dog’s meals sometimes satisfies the craving. This is worth trying before treating it as a problem that needs solving.
Matching the walk to the dog
Dogs that are under-stimulated on walks sometimes eat grass out of boredom. A walk with sniffing time, varied routes, and an appropriate length for the dog’s breed and age is less likely to produce compulsive grazing. The walk-length calculator helps set a baseline that fits your dog’s needs.
Golden Retrievers, for example, need enough physical and mental engagement on a walk that a few blades of grass are a passing interest, not the main activity.
If you are curious about how meal timing and walks interact more broadly, see walk before or after meals.
For more on the research behind diet, digestion, and exercise in dogs, see our sources.