Vomiting is a forceful expulsion of stomach contents through the mouth, and is different from regurgitation—the effortless return of stomach contents to the mouth.
Vomiting is a symptomatic response to a number of harmful triggers. Although unpleasant, vomiting is an important function because it rids the body of harmful substances. Vomiting, along with nausea, is a symptom of an underlying disease rather than a specific illness itself. Causes of vomiting are varied and include foodborne illnesses, infections, problems with the brain and central nervous system, and systemic (body-wide) diseases. Some illnesses will cause nausea and vomiting, even though there is no direct involvement of the stomach or gastrointestinal tract. Vomiting may be a side effect of medications, including drugs used in cancer chemotherapy, as well as a side effect of radiation therapy.</p