There are many reasons why a dog (or cat) may eat grass. However, most veterinarians’ consensus is that pets will eat grass as a way to reduce, eliminate or relieve GI upset, nausea, parasites or possibly infection. Many pets will eat grass and then vomit. It’s the purging act that the pet seeks. Generally, the pet will feel better after vomiting. Seek veterinary care if this is occurring on a repeatable basis.
Another school of thought is that these pets may be craving a nutrient that they are not getting with their diet and is found in grass.
Lastly, some pets may just like the taste of chlorophyll in the grass or the texture of the grass blades.