Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Nausea is a sensation of unease and discomfort in the upper stomach with an urge to vomit. An attack of nausea is known as a qualm. The most common cause is gastroenteritis ( a stomach infection ) or food poisoning but nausea also frequently occurs as a medication side effect and in pregnancy. A number of medication exist that improve symptoms including: dimenhydrinate, metoclopramide, and ondansetron. The causes of nausea are many. One organization listed 700 in 2009. Gastrointestinal infections (37%) and food poisoning are the two most common causes. While side effects from medications (3%) and pregnancy are also relatively frequent. In 10% of people the cause remains unknown.