Nausea is not a sickness, but rather a symptom of several conditions, many of which are not related to the stomach. Nausea is often indicative of an underlying condition elsewhere in the body. Travel sickness, which is due to confusion between perceived movement and actual movement, is an example. The sense of equilibrium lies in the ear and works together with eyesight. When these two don't "agree" to what extent the body is actually moving the symptom is presented as nausea even though the stomach itself has nothing to do with the situation. The reason for the stomach's involvement is thought to be the brain concluding that one of the senses is hallucinating, and further conclude that this is due to poison ingestion. The brain then induces vomiting to clear the supposed toxin.
In medicine, nausea can be a problem during some chemotherapy regimens and following general anaesthesia. Nausea is also a common symptom of pregnancy, in which it is called "morning sickness." Mild nausea experienced during pregnancy can be normal, and should not be considered an immediate cause for alarm.
Other causes of nausea:
Symptomatic treatment for nausea and vomiting may include short-term avoidance of solid food. This is usually easy as nausea is nearly always associated with loss of appetite. If the patient is dehydrated, rehydration with oral or intravenous electrolyte solutions may be required. If the cause of the nausea is motion sickness, then sitting down in a still environment may also help.
There are several types of antiemetics, and researchers continue to look for more effective treatments. The main types used post-operatively for surgical patients are ondansetron, dexamethasone, promethazine, diphenhydramine, and in small doses droperidol. Doxylamine is the drug of choice in pregnancy-related nausea. When ingested or inhaled, marijuana has been shown to reduce nausea in the majority of users. Also available are a variety of non-invasive, but often untested, mechanical devices for suppressing nausea due to motion sickness.