What causes hairballs?

Vomiting (also throwing up or emesis) is the forceful expulsion of the contents of one's stomach through the mouth. Vomiting may result from many causes, ranging from gastritis or poisoning to brain tumors, or elevated intracranial pressure (ICP). The feeling that one is about to vomit is called nausea. It usually precedes vomiting, but it does not always lead to vomiting. Antiemetics are sometimes necessary to suppress nausea and vomiting, and in severe cases where dehydration develops, intravenous fluid may need to be administered.