Food - If their diet has changed, they may vomit if they aren't used to the new food. Or, more commonly, they vomit fairly often if the diet they're on isn't suitable for their nutritional needs. This happens often with the cheapest grades of kibble found at the grocery store, as a rule. But even expensive dry foods can upset their stomachs if the ingredients are not appropriate for them. For example, the first ingredient should be a good quality protein, such as some kind of meat. It should not be a grain, such as corn, wheat or soy. In fact, any grains in the formula are not necessary for good nutrition, but the companies put it in to make it easier and cheaper to manufacture dry food.

Activities - If your kitty is an indoor/outdoor cat, be certain your yard is safe and free from toxins, including toxic plants. In fact, be sure to keep toxic plants out of reach in your home, too. Cats seem to enjoy eating grass, so they will almost certainly do that while playing or roaming around the yard. It's so common, it's probably safe, as long as there are no chemicals used on the lawn for pest or weed control. Be sure kitty isn't nosing around in the garage or the gardening shed, either, as there are usually chemicals in there they should not have access to.

Health - If kitty has recently been spayed or neutered, or vaccinated at the vet's, they may have a short term reaction to the procedure. Be sure to ask your vet about it, especially if the vomiting is severe or lasts more than a few days. If there have been no recent vet visits, it might be time for one! Getting a wellness exam from time to time is always a good idea, too.