Nausea and vomiting after tooth extraction is usually caused by biting the cotton ball, the taste of blood in the mouth or the stimulation of anesthesia. 1. Bite cotton ball: after the tooth extraction, you need to bite cotton ball to stop bleeding, cotton ball as a foreign body in the mouth, may cause discomfort in the pharynx, resulting in nausea and vomiting feeling. 2. Oral blood odor: after tooth extraction, there will be a small amount of blood in the extraction socket of the mouth, and the blood odor may cause nausea and vomiting. 3. Stimulation of anesthesia: some of the symptoms of nausea and vomiting may occur due to the stimulation of anesthesia drugs. Generally speaking, nausea and vomiting after tooth extraction does not require special treatment, when other systemic reactions occur, it is recommended to consult a doctor in time, under the guidance of the doctor for treatment.