Nausea is a general term describing a queasy stomach, with or without the feeling that you are about to vomit. Almost everyone experiences nausea at some time, making it one of the most common problems in medicine. Nausea is not a disease, but a symptom of many different disorders. It is caused by problems in any one of three parts of the body, including:
Abdominal and pelvic organs — Many different abdominal conditions can cause nausea. Common abdominal causes of nausea include inflammation of the liver (hepatitis) or pancreas (pancreatitis); a blocked or stretched intestine or stomach; gastroesophageal reflux (GERD); irritation of the stomach, intestinal lining, appendix or pelvic organs; inflammation of the kidney; and gallbladder problems. The most common abdominal illnesses that result in nausea are viral infections (gastroenteritis). Nausea also can be caused by constipation and normal menstruation.
Brain and spinal fluid
Nausea is common with migraine headaches, head injury, brain tumors, stroke, bleeding into or around the brain and meningitis (inflammation or infection of the membranes covering the brain). It can be a symptom of glaucoma, resulting from pressure on the nerves at the back of the eye. It sometimes is a brain reaction triggered by pain, significant emotional distress or exposure to unpleasant sights or odors.
Balance centers in the inner ear — Nausea can be related to vertigo, a dizzy sensation of spinning, moving or falling when you are not moving. Common conditions that cause vertigo include motion sickness (triggered by repeated movements in different directions inside a car, boat, train, plane or amusement ride), viral infections of the inner ear (labyrinthitis), sensitivity to position change (benign positional vertigo) and certain brain or nerve tumors.
Nausea also is a common side effect of some body chemical changes:
Reproductive hormones — About 50% of women experience morning sickness during the first few months of pregnancy, and it is a common side effect of birth control pills.
Medications — Many medicines (including prescription, over-the-counter and herbal medicines) commonly cause nausea as a side effect, especially when more than one medication is taken at the same time. Chemotherapy drugs and antidepressants are among the medicines that frequently cause nausea.
Low blood sugar — Nausea is common with low blood sugar.
Alcohol use — Both alcohol intoxication and alcohol withdrawal, including a hangover, can cause nausea.
Anesthesia — Some people experience nausea while awakening from surgery and recovering from anesthesia.
Food allergies and food poisoning — In food poisoning, small amounts of bacteria in contaminated food produce irritating toxins that cause nausea and abdominal cramps.