Nausea is a condition of generalized malaise that often occurs before vomiting. Its onset may reveal an organic disease of the digestive tract (stenosidel pylorus or intestine) or of the central nervous system (endocranial hypertension).
It may also occur in non-pathological circumstances: at the beginning of pregnancy, as a result of hormonal changes, or during a journey (by air, ship, etc.) due to the movement of fluids in the inner ear. When the malaise continues over time without vomiting or other organic signs arising, this may be a psychological symptom that expresses a feeling of disgust and rejection.