Nausea is a feeling of discomfort in the upper abdomen and an urge to vomit, while dry heaving occurs after nausea and may produce vomiting movements and sounds, but is not accompanied by the expulsion of the contents of the stomach and intestines through the mouth. The two often occur together and are accompanied by abdominal pain, diarrhoea, fever, sweating and vomiting of gastrointestinal contents.