Nausea is difficult for many people to describe. It is a very uncomfortable, but not painful, feeling that is felt in the back of the throat, the chest or the upper abdomen. The feeling is associated with distaste for food or an urge to vomit. When the body prepares to vomit, the following sequence may occur:
The muscular ring between the esophagus and stomach (esophageal sphincter) relaxes.
The abdominal muscles and diaphragm contract.
The windpipe (larynx) closes.
The lower portion of the stomach contracts.
When a person vomits, the stomach contents are expelled through the esophagus and mouth.
As a result of these body actions, when you have nausea you experience retching. Retching is repeated rhythmic contractions of respiratory and abdominal muscles that occur without your control. You may or may not vomit. Profuse sweating sometimes accompanies nausea.