Why do dogs eat grass?

Some dogs seem to have an appetite for grass, particularly for fresh Spring grass. Others eat it when they feel nauseous. It is normal for dogs to eat grass when they feel sick but it is not normal for them to vomit. Usually there are other signs of gastrointestinal upset (such as poor appetite, vomiting and diarrhoea) in conjunction with grass consumption. Vomiting and diarrhoea can be due to inflammatory conditions of the stomach and intestines, sudden dietary change, parasites, etc, but can also be symptoms of a more sinister disease.