Canker sores usually drain the pus in about two weeks and heal completely in about four weeks, but the exact time is affected by the severity of the condition and the method of treatment, which varies slightly from patient to patient. Most canker sores are caused by bacterial infections, and the severity of the condition will affect the recovery time. Generally, it can become pus in 3~5 days, can finish draining the pus in about two weeks, and can completely heal in about four weeks, but it is not absolute. During the recovery period, it is also necessary to cooperate with the active treatment of medication, to ensure that the injured area is ventilated and not sealed, which can be conducive to recovery. If the situation is more serious, and if the patient is malnourished or diabetic, the healing time will be prolonged accordingly. In addition, if the local protection is not in place during the recovery period, it can lead to complications or aggravate pus, and the time for pus drainage will also be prolonged. Eating more fresh fruits and vegetables, paying more attention to hygiene and dietary habits, and allowing the injured area to get a good recovery environment may shorten the time of pus drainage. If there are complications or poor recovery during treatment, it is recommended that treatment be carried out under the guidance of a doctor’s examination to avoid delaying the condition.