|A 1681 painting depicting a person vomiting|
Nausea is a diffuse sensation of unease and discomfort, often perceived as an urge to vomit.  While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, upper abdomen, or back of the throat. 
Over 30 definitions of nausea were proposed in a 2011 book on the topic. 
Nausea is a non-specific symptom, which means that it has many possible causes. Some common causes of nausea are gastroenteritis and other gastrointestinal disorders, food poisoning, motion sickness, dizziness, migraine, fainting, low blood sugar and lack of sleep. Nausea is a side effect of many medications including chemotherapy, or morning sickness in early pregnancy. Nausea may also be caused by disgust and depression. 
Medications taken to prevent and treat nausea are called antiemetics. The most commonly prescribed antiemetics in the US are promethazine, metoclopramide and the newer, extremely effective ondansetron. The word nausea is from Latin nausea, from Greek ναυσία – nausia,  "ναυτία" – nautia, motion sickness, "feeling sick or queasy". 
Gastrointestinal infections (37%) and food poisoning are the two most common causes of acute nausea and vomiting.  Side effects from medications (3%) and pregnancy are also relatively frequent.  There are many causes of chronic nausea.  Nausea and vomiting remain undiagnosed in 10% of the cases. Aside from morning sickness, there are no sex differences in complaints of nausea. After childhood, doctor consultations decrease steadily with age. Only a fraction of one percent of doctor visits by those over 65 are due to nausea. 
Gastrointestinal infection is one of the most common causes of acute nausea and vomiting.  Chronic nausea may be the presentation of many gastrointestinal disorders, occasionally as the major symptom, such as gastroesophageal reflux disease, functional dyspepsia, gastritis, biliary reflux, gastroparesis, peptic ulcer, celiac disease, non-celiac gluten sensitivity, Crohn's disease, hepatitis, upper gastrointestinal malignancy, and pancreatic cancer.   Uncomplicated Helicobacter pylori infection does not cause chronic nausea. 
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. 
Many medications can potentially cause nausea.  Some of the most frequently associated include cytotoxic chemotherapy regimens for cancer and other diseases, and general anaesthetic agents. An old cure for migraine, ergotamine, is well known to cause devastating nausea in some patients; a person using it for the first time will be prescribed an antiemetic for relief if needed.
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 sexually active woman of child-bearing age.  While usually it is mild and self-limiting, severe cases known as hyperemesis gravidarum may require treatment. 
Dysmenorrhea can cause nausea. 
While most causes of nausea are not serious, some serious conditions are associated with nausea. These include pancreatitis, small bowel obstruction, appendicitis, cholecystitis, hepatitis, Addisonian crisis, diabetic ketoacidosis, increased intracranial pressure, spontaneous intracranial hypotension, brain tumors, meningitis, heart attack, rabies  carbon monoxide poisoning and many others. 
- Gastric outlet obstruction
- Small bowel obstruction
- Colonic obstruction
- Superior mesenteric artery syndrome
- Intestinal pseudo-obstruction
- Gastroesophageal reflux disease
- Irritable bowel syndrome
- Cyclic vomiting syndrome
Taking a thorough patient history may reveal important clues to the cause of nausea and vomiting. If the patient's symptoms have an acute onset, then drugs, toxins, and infections are likely. In contrast, a long-standing history of nausea will point towards a chronic illness as the culprit. The timing of nausea and vomiting after eating food is an important factor to pay attention to. Symptoms that occur within an hour of eating may indicate an obstruction proximal to the small intestine, such as gastroparesis or pyloric stenosis. An obstruction further down in the intestine or colon will cause delayed vomiting. An infectious cause of nausea and vomiting such as gastroenteritis may present several hours to days after the food was ingested.  The contents of the emesis is a valuable clue towards determining the cause. Bits of fecal matter in the emesis indicate obstruction in the distal intestine or the colon. Emesis that is of a bilious nature (greenish in color) localizes the obstruction to a point past the stomach. Emesis of undigested food points to an obstruction prior to the gastric outlet, such as achalasia or Zenker's diverticulum. If patient experiences reduced abdominal pain after vomiting, then obstruction is a likely etiology. However, vomiting does not relieve the pain brought on by pancreatitis or cholecystitis. 
It is important to watch out for signs of dehydration, such as orthostatic hypotension and loss of skin turgor. Auscultation of the abdomen can produce several clues to the cause of nausea and vomiting. A high-pitched tinkling sound indicates possible bowel obstruction, while a splashing " succussion" sound is more indicative of gastric outlet obstruction. Eliciting pain on the abdominal exam when pressing on the patient may indicate an inflammatory process. Signs such as papilledema, visual field losses, or focal neurological deficits are red flag signs for elevated intracranial pressure. 
When a history and physical exam are not enough to determine the cause of nausea and vomiting, certain diagnostic tests may prove useful. A chemistry panel would be useful for electrolyte and metabolic abnormalities.  Liver function tests and lipase would identify pancreaticobiliary diseases.  Abdominal X-rays showing air-fluid levels indicate bowel obstruction, while an X-ray showing air-filled bowel loops are more indicative of ileus. More advanced imaging and procedures may be necessary, such as a CT scan, upper endoscopy, colonoscopy, barium enema, or MRI. Abnormal GI motility can be assessed using specific tests like gastric scintigraphy, wireless motility capsules, and small-intestinal manometry. 
Research on nausea and vomiting has relied on using animal models to mimic the anatomy and neuropharmacologic features of the human body.  The physiologic mechanism of nausea is a complex process that has yet to be fully elucidated. There are four general pathways that are activated by specific triggers in the human body that go on to create the sensation of nausea and vomiting. 
- Central nervous system (CNS): Stimuli can affect areas of the CNS including the cerebral cortex and the limbic system. These areas are activated by elevated intracranial pressure, irritation of the meninges (i.e. blood or infection), and extreme emotional triggers such as anxiety. The supratentorial region is also responsible for the sensation of nausea. 
- Chemoreceptor trigger zone (CTZ): The CTZ is located in the area postrema in the floor of the fourth ventricle within the brain. This area is outside the blood brain barrier, and is therefore readily exposed to substances circulating through the blood and cerebral spinal fluid. Common triggers of the CTZ include metabolic abnormalities, toxins, and medications. Activation of the CTZ is mediated by dopamine (D2) receptors, serotonin (5HT3) receptors, and neurokinin receptors (NK1).
- Vestibular system: This system is activated by disturbances to the vestibular apparatus in the inner ear. These include movements that cause motion sickness and dizziness. This pathway is triggered via histamine (H1) receptors and acetylcholine (ACh) receptors.
- Peripheral Pathways: These pathways are triggered via chemoreceptors and mechanoreceptors in the gastrointestinal tract, as well as other organs such as the heart and kidneys. Common activators of these pathways include toxins present in the gastrointestinal lumen and distension of the gastrointestinal lumen from blockage or dysmotility of the bowels. Signals from these pathways travel via multiple neural tracts including the vagus, glossopharyngeal, splanchnic, and sympathetic nerves.
Signals from any of these pathways then travel to the brainstem, activating several structures including the nucleus of the solitary tract, the dorsal motor nucleus of the vagus, and central pattern generator.  These structures go on to signal various downstream effects of nausea and vomiting. The body's motor muscle responses involve halting the muscles of the gastrointestinal tract, and in fact causing reversed propulsion of gastric contents towards the mouth while increasing abdominal muscle contraction. Autonomic effects involve increased salivation and the sensation of feeling faint that often occurs with nausea and vomiting.
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.  Medical care is recommended if: a person cannot keep any liquids down, has symptoms more than 2 days, is weak, has a fever, has stomach pain, vomits more than two times in a day or does not urinate for more than 8 hours. 
Many pharmacologic medications are available for the treatment of nausea. There is no medication that is clearly superior to other medications for all cases of nausea.  The choice of antiemetic medication may be based on the situation during which the person experiences nausea. For people with motion sickness and vertigo, antihistamines and anticholinergics such as meclizine and scopolamine are particularly effective.  Nausea and vomiting associated with migraine headaches respond best to dopamine antagonists such as metoclopramide, prochlorperazine, and chlorpromazine.  In cases of gastroenteritis, serotonin antagonists such as ondansetron were found to suppress nausea and vomiting, as well as reduce the need for IV fluid resuscitation.  The combination of pyridoxine and doxylamine is the first line treatment for pregnancy-related nausea and vomiting.  Dimenhydrinate is an inexpensive and effective over the counter medication for preventing postoperative nausea and vomiting.  Other factors to consider when choosing an antiemetic medication include the person's preference, side-effect profile, and cost.
Nabilone is also indicated for this purpose.
In certain people, cannabinoids may be effective in reducing chemotherapy associated nausea and vomiting.   Several studies have demonstrated the therapeutic effects of cannabinoids for nausea and vomiting in the advanced stages of illnesses such as cancer and AIDS.  
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. 
The outlook depends on the cause. Most people recover within few hours or a day. 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 or dangerous electrolyte imbalances or both. 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.  In Australia, nausea, as opposed to vomiting, occurs most frequently in persons aged 15–24 years, and is less common in other age groups. 
- Metz A, Hebbard G (September 2007). "Nausea and vomiting in adults--a diagnostic approach" (PDF). Australian Family Physician (Review). Royal Australian College of General Practitioners. 36 (9): 688–92. PMID 17885699.
- Balaban CD, Yates BJ (January 2017). "What is nausea? A historical analysis of changing views". Autonomic Neuroscience. 202: 5–17. doi: 10.1016/j.autneu.2016.07.003. PMC 5203950. PMID 27450627.
- Liddell, Henry George; Scott, Robert. "ναυσία". A Greek-English Lexicon – via Perseus.tufts.edu.
- Liddell, Henry George; Scott, Robert. "ναυτία". A Greek-English Lexicon – via perseus.tufts.edu.
- Britt H, Fahridin S (September 2007). "Presentations of nausea and vomiting" (PDF). Australian Family Physician. 36 (9): 682–3. PMID 17885697.
- Volta U, Caio G, Karunaratne TB, Alaedini A, De Giorgio R (January 2017). "Non-coeliac gluten/wheat sensitivity: advances in knowledge and relevant questions". Expert Review of Gastroenterology & Hepatology (Review). 11 (1): 9–18.
A lower proportion of NCG/WS patients (from 30% to 50%) complain of upper gastrointestinal tract manifestations, e.g. vomiting, nausea, gastroesophageal reflux disease, aerophagia and aphthous stomatitis. (NCG/WS: Non-coeliac gluten/wheat sensitivity)
- Scorza K, Williams A, Phillips JD, Shaw J (July 2007). "Evaluation of nausea and vomiting". American Family Physician. 76 (1): 76–84. PMID 17668843.
- Koch KL, Frissora CL (March 2003). "Nausea and vomiting during pregnancy". Gastroenterology Clinics of North America. 32 (1): 201–34, vi. doi: 10.1016/S0889-8553(02)00070-5. PMID 12635417.
- Sheehan P (September 2007). "Hyperemesis gravidarum--assessment and management". Australian Family Physician. 36 (9): 698–701. PMID 17885701.
- Osayande AS, Mehulic S (March 2014). "Diagnosis and initial management of dysmenorrhea". American Family Physician. 89 (5): 341–6. PMID 24695505.
- Singh P, Yoon SS, Kuo B (January 2016). "Nausea: a review of pathophysiology and therapeutics". Therapeutic Advances in Gastroenterology (Review). 9 (1): 98–112. doi: 10.1177/1756283X15618131. PMC 4699282. PMID 26770271.
- O'Connor RE, Brady W, Brooks SC, Diercks D, Egan J, Ghaemmaghami C, et al. (November 2010). "Part 10: acute coronary syndromes: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care". Circulation. 122 (18 Suppl 3): S787-817. doi: 10.1161/circulationaha.110.971028. PMID 20956226.
- Hasler WL. Nausea, Vomiting, and Indigestion. In: Kasper D, Fauci A, Hauser S, Longo D, Jameson J, Loscalzo J. eds. 'Harrison's Principles of Internal Medicine, 19e. New York, NY: McGraw-Hill; 2015.
- Porter, Ryan. "Nausea and Vomiting" (PDF). Med.unc.edu. American College of Gastroenterology. Archived from the original (PDF) on 28 March 2017. Retrieved 24 January 2018.
- Andrews PL, Horn CC (April 2006). "Signals for nausea and emesis: Implications for models of upper gastrointestinal diseases". Autonomic Neuroscience. 125 (1–2): 100–15. doi: 10.1016/j.autneu.2006.01.008. PMC 2658708. PMID 16556512. Retrieved 2015-01-11.
- Lien, C (2012). Principles and Practice of Hospital Medicine. New York, NY: McGraw HIll. pp. Chapter 217: Domains of Care: Physical Aspects of Care.
- Bashashati M, McCallum RW (January 2014). "Neurochemical mechanisms and pharmacologic strategies in managing nausea and vomiting related to cyclic vomiting syndrome and other gastrointestinal disorders". European Journal of Pharmacology. 722: 79–94. doi: 10.1016/j.ejphar.2013.09.075. PMID 24161560.
- "When you have nausea and vomiting: MedlinePlus Medical Encyclopedia". Nlm.nih.gov. Retrieved 2014-03-20.
- Furyk JS, Meek RA, Egerton-Warburton D (September 2015). "Drugs for the treatment of nausea and vomiting in adults in the emergency department setting". The Cochrane Database of Systematic Reviews. 9 (9): CD010106. doi: 10.1002/14651858.cd010106.pub2. PMC 6517141. PMID 26411330.
- Flake ZA, Linn BS, Hornecker JR (March 2015). "Practical selection of antiemetics in the ambulatory setting". American Family Physician. 91 (5): 293–6. PMID 25822385. Retrieved 10 November 2015.
- Kranke P, Morin AM, Roewer N, Eberhart LH (March 2002). "Dimenhydrinate for prophylaxis of postoperative nausea and vomiting: a meta-analysis of randomized controlled trials". Acta Anaesthesiologica Scandinavica. 46 (3): 238–44. doi: 10.1034/j.1399-6576.2002.t01-1-460303.x. PMID 11939912.
- Tramèr MR, Carroll D, Campbell FA, Reynolds DJ, Moore RA, McQuay HJ (July 2001). "Cannabinoids for control of chemotherapy induced nausea and vomiting: quantitative systematic review". BMJ. 323 (7303): 16–21. doi: 10.1136/bmj.323.7303.16. PMC 34325. PMID 11440936.
- Drug Policy Alliance (2001). "Medicinal Uses of Marijuana: Nausea, Emesis and Appetite Stimulation". Archived from the original on 2007-08-05. Retrieved 2007-08-02.
- World health Organization, Cannabis - epidemiology. http://www.who.int/substance_abuse/facts/cannabis/en/
- Whiting PF, Wolff RF, Deshpande S, Di Nisio M, Duffy S, Hernandez AV, et al. (2015-06-23). "Cannabinoids for Medical Use: A Systematic Review and Meta-analysis". JAMA. 313 (24): 2456–73. doi: 10.1001/jama.2015.6358. PMID 26103030.
American Academy of Hospice and Palliative Medicine,
"Five Things Physicians and Patients Should Question",
Choosing Wisely: an initiative of the
American Academy of Hospice and Palliative Medicine, retrieved August 1, 2013, which cites
- Smith TJ, Ritter JK, Poklis JL, Fletcher D, Coyne PJ, Dodson P, Parker G (May 2012). "ABH gel is not absorbed from the skin of normal volunteers". Journal of Pain and Symptom Management. 43 (5): 961–6. doi: 10.1016/j.jpainsymman.2011.05.017. PMID 22560361.
- Weschules DJ (December 2005). "Tolerability of the compound ABHR in hospice patients". Journal of Palliative Medicine. 8 (6): 1135–43. doi: 10.1089/jpm.2005.8.1135. PMID 16351526.
- Marx WM, Teleni L, McCarthy AL, Vitetta L, McKavanagh D, Thomson D, Isenring E (April 2013). "Ginger (Zingiber officinale) and chemotherapy-induced nausea and vomiting: a systematic literature review" (PDF). Nutrition Reviews. 71 (4): 245–54. doi: 10.1111/nure.12016. PMID 23550785.
- Ernst E, Pittler MH (March 2000). "Efficacy of ginger for nausea and vomiting: a systematic review of randomized clinical trials" (PDF). British Journal of Anaesthesia. 84 (3): 367–71. doi: 10.1093/oxfordjournals.bja.a013442. PMID 10793599.
- "Bulimia Nervosa-Topic Overview". WebMD. Archived from the original on 25 July 2012. Retrieved 26 July 2012.
- The dictionary definition of nausea at Wiktionary