nausea is a symptom, rather than an illness or disease. the causes for it very often are not in the stomach itself, but somewhere else in the body. nausea is often caused by a stomach virus. nausea is usually harmless, in the short term. a good treatment for it can be not to take solid food (and to only drink non-alcoholic drinks, like water). nausea can also occur during pregnancy, and is quite normal in that context. people can suffer nausea without vomiting.