Nausea and vomiting may be caused by improper diet, food poisoning, gastroenteritis, gastric ulcer and other reasons. 1. Improper diet: nausea and vomiting can be caused when patients overeat or consume moldy, too greasy and spicy food. 2. Food poisoning: nausea and vomiting can occur after eating food contaminated by bacteria or mixed with toxins. 3. Gastroenteritis: Gastroenteritis is caused by viral and bacterial infections and is mainly manifested by nausea, vomiting, abdominal pain, diarrhea and other symptoms. 4. Gastric ulcer: If the ulcer area is large, causing congestion and edema of the surrounding mucosa, affecting gastrointestinal peristalsis, it can also lead to nausea and vomiting symptoms. The symptoms of nausea and vomiting should go to the hospital in time for relevant examinations, under the guidance of professional physicians to clarify the cause of the disease, so as not to delay the condition.