Nausea is the sensation of feeling like you are about to vomit. Vomiting, or emesis, is the expelling of undigested food through the mouth.

Occasional nausea can have a number of causes, including overeating, drinking too much alcohol, infection, and stress. Morning sickness is a type of nausea caused by pregnancy-related hormone changes. Some people experience motion sickness when riding in a car or traveling by plane or boat. Certain medicines, including cancer chemotherapy drugs also cause nausea.

Mild nausea can often be relieved by getting some fresh air or eating bland crackers. Vomiting relieves nausea right away, but can cause dehydration. Sipping clear juices, weak tea, and some sports drinks help replace lost fluid and minerals without irritating the stomach. After a period of nausea and vomiting, food should be reintroduced gradually, beginning with small amounts of dry, bland food like crackers and...