Usually it’s normal dog behaviour — they like the taste and texture, it adds a little fibre, and some do it out of boredom. Despite the myth, most grass-eating dogs are not sick and don’t vomit afterwards.
The most common belief is that dogs eat grass to make themselves sick. Surveys of dog owners actually show the opposite: the large majority of dogs that eat grass show no signs of illness beforehand, and only a small minority vomit afterwards. So while an occasional dog may graze when their tummy feels off, for most it’s simply something they enjoy doing.
Dogs are natural scavengers and their wild ancestors ate plant matter as part of a varied diet. Fresh grass has a taste and a satisfying crunch, and a little extra fibre can feel good for digestion. Many dogs are pickier than you’d think — they’ll seek out certain patches and ignore others, which suggests genuine preference rather than desperation.
A bored dog on a long, dull walk may graze the way a bored person nibbles snacks. More exercise, sniffing time, training games and chew toys often reduce idle grass-eating. If your dog races to eat grass the moment they’re understimulated, the grass may be a symptom of needing more to do rather than a dietary need.
Grass-eating itself is rarely harmful, but two things are worth watching. First, avoid lawns treated with pesticides, herbicides or fertilisers, which can be toxic. Second, if grass-eating suddenly becomes frantic, is paired with lots of vomiting, lip-licking or a change in appetite, see your vet — that can point to nausea or a digestive problem rather than ordinary grazing.
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Most quirks are perfectly normal. If a behaviour changes suddenly or comes with other signs of illness, check with your vet. Full disclaimer.