Why Is My Dog Eating Grass? What the Evidence Says

Grass-eating is one of the most common behaviours owners ask about, and one of the least well understood. Surveys suggest that the majority of dogs eat grass at least occasionally, and most do so without any apparent ill effects. The behaviour has attracted various theories but no definitive scientific consensus.

Should I Be Concerned?

Grass-eating rarely requires an urgent vet visit. However, contact your vet if:

• Your dog is eating large amounts of grass compulsively and very frequently
• Grass-eating is consistently followed by vomiting
• Your dog seems unwell alongside the grass-eating: lethargic, off food, or in apparent discomfort
• You are in an area where grass may have been treated with herbicides, pesticides, or fertilisers

Occasional grass-eating in an otherwise healthy, well-behaved dog is generally nothing to worry about.

What Causes Dogs to Eat Grass?

Instinctive or ancestral behaviour

Wild canids regularly consume the stomach contents of herbivore prey, which includes partly digested plant material. Grass-eating may be a remnant of this behaviour, though this theory is difficult to prove in domesticated dogs.

Fibre supplementation

Some researchers suggest dogs eat grass to increase dietary fibre. Dogs that eat grass but rarely vomit afterwards may be addressing a nutritional need. If your dog eats grass frequently, it may be worth discussing dietary fibre intake with your vet.

Digestive discomfort

A proportion of dogs seem to eat grass selectively when experiencing nausea or digestive discomfort, and may vomit shortly afterwards. However, studies suggest that most dogs eat grass without vomiting, and the causal link is not consistent.

Boredom or pica

Some dogs eat grass out of boredom, particularly on long walks with limited stimulation, or as part of a generalised tendency to consume non-food items (pica). If grass-eating is one of several non-food items being consumed, speak to your vet.

It tastes good

There is evidence that some dogs simply enjoy the taste or texture of grass, particularly young, tender spring growth. This is the most straightforward explanation and is difficult to disprove.

Which Breeds Are More Prone to Grass-Eating?

Grass-eating is reported across all breeds and sizes. There is no strong evidence that specific breeds are significantly more prone to it. Dogs with a tendency towards pica (consuming non-food items) generally may eat grass more frequently.

What Will the Vet Do?

Your vet is unlikely to recommend any action for occasional, symptom-free grass-eating. If grass-eating is compulsive or consistently associated with vomiting, they may:

• Review your dog's diet and consider a higher-fibre food
• Screen for gastrointestinal disease if digestive symptoms are frequent
• Discuss behavioural management if pica is suspected

What Can You Do?

• Ensure the grass your dog has access to is untreated by herbicides or pesticides
• If your dog eats grass and then vomits regularly, keep a diary and mention it at your next vet visit
• If the behaviour is excessive or compulsive, ensure your dog has adequate mental and physical stimulation
• A high-quality diet with appropriate fibre content may reduce the frequency in some dogs
• Do not discourage grass-eating in otherwise healthy dogs, as there is no evidence it is harmful and may serve a useful purpose