Nausea (Latinnausea, from Greekναυσία - nausia, "ναυτία" - nautia, motion sickness", "feeling sick," "queasy" or "wamble") is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting. A person can suffer nausea without vomiting. (Greek ναῦς - naus, "ship"; ναυσία started as meaning "seasickness".)
Food poisoning usually causes an abrupt onset of nausea and vomiting one to six hours after ingestion of contaminated food and lasts for one to two days. It is due to toxins produced by bacteria in food.
Nausea or "morning sickness" is common during early pregnancy but may occasionally continue into the second and third trimesters. In the first trimester nearly 80% of women have some degree of nausea. Pregnancy should therefore be considered as a possible cause of nausea in any women of child bearing age. While usually it is mild and self-limiting severe cases known as hyperemesis gravidarum may require treatment.
Often no investigations are needed, however basic lab tests may be appropriate. If a bowel obstruction is possible, abdominal x-rays may be useful.
If dehydration is present due to loss of fluids from severe vomiting, rehydration with oral electrolyte solutions is preferred. If this is not effective or possible, intravenous rehydration may be required. NIH Medline recommends drinking clear fluids, sitting quietly and eating bland foods.  Medline recommends you call a doctor if you:
In hospital settings topical anti-nausea gels are not indicated because of lack of research backing their efficacy. Topical gels containing lorazepam, diphenhydramine, and haloperidol are sometimes used for nausea but are not equivalent to more established therapies.
While short-term nausea and vomiting are generally harmless, they may sometimes indicate a more serious condition. When associated with prolonged vomiting, it may lead to dehydration and/or dangerous electrolyte imbalances. Repeated intentional vomiting, characteristic of bulimia, can cause stomach acid to wear away at the enamel in teeth.
Nausea and or vomiting is the main complaint in 1.6% of visits to family physicians in Australia. However only 25% of people with nausea visit their family physician. It is most common in those 15–24 years old and less common in other ages.
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