For most dogs eating grass is likely nothing to be concerned with as long as the grass has not been treated with pesticides, herbicides or other chemicals. Grass eating is common for dogs and it is not always related to illness or vomiting.
Grass eating most likely falls into one of three categories.
They enjoy it. (Vegetation is good and serves a biological purpose)
One benefit of grass eating is that “Plant chlorophyll can bind mycotoxins, such as hose found in moldy grains, decreasing their absorption.” “Mycotoxin contamination in pet food poses a serious health threat to pets.”
Some dogs showing signs of illness before eating grass are more likely to vomit afterward.
My two dogs always loved to eat grass and we would say they just liked their salad and that it was normal. But after running a NutriScan food intolerance test on each of them and eliminating several foods from their diet their grass eating reduced about 95%. (after eating grass they were not throwing up). Since food intolerance or sensitivity is more common than a food allergy I plan on running a NutriScan test on all my future dogs for food intolerances since it seems reasonable that problems can be subclinical for a length of time. Food intolerances/sensitivities can manifest in gastrointestinal issues, chronic itching, chronic gas, chronic skin, ear and foot infections.
If your dog does eat grass on occasion just be sure that it has not been treated with pesticides, herbicides or other chemicals because studies have linked canine cancers to lawn chemicals.
CANCER LINK TO LAWN CHEMICALS