Nausea is a neurological reflex that is formed by a wave of retrograde gastric peristalsis caused by various causes of irritation, which manifests as nausea and vomiting. We can also experience nausea when we normally see something that makes us uncomfortable, which is a conditioned reflex. Therefore, in many cases, nausea is not necessarily pathological.
The common cause of nausea in pathological situations is gastroesophageal reflux, including acid reflux, food reflux, and non-acid reflux, which is often accompanied by acid reflux, belching, and epigastric distention.
Another common cause is obstruction or incomplete obstruction of the gastrointestinal tract, which leads to nausea and vomiting due to increased pressure from the increased contents of the gastrointestinal tract, such as pyloric duct ulcers, gastric cancer, etc.
Other systemic diseases can also manifest as nausea, commonly liver and kidney insufficiency, electrolyte disturbances, advanced tumors, pregnancy, respiratory infections, etc.