Mouth ulcers usually do not heal in two days. It usually takes 10 to 14 days to heal. In the case of traumatic ulcers, cancerous ulcers, or tuberculous ulcers, appropriate treatment to remove traumatic factors, surgical treatment, and anti-tuberculous treatment is required, otherwise they cannot heal. Common mouth ulcers are usually recurrent aphthous ulcers, which are self-limiting and last for 10-14 days. The use of chlorhexidine solution, compound borax solution, healing new solution, dexamethasone spray, etc. can promote the healing of mouth ulcers. Traumatic ulcers, cancerous ulcers, and tuberculous ulcers are not self-limiting and will not heal without appropriate treatment. Traumatic ulcers need to remove traumatic factors, such as residual roots and crowns, bad restorations, etc. Cancer ulcers need surgical treatment, and tuberculosis ulcers need anti-tuberculosis treatment, such as isoniazid, rifampicin, etc. All of the above medications need to be prescribed by a doctor to promote the healing of mouth ulcers. All of the above medications should be used under the guidance of a doctor. If the mouth ulcers remain unhealed for a long time, it is recommended to go to the hospital in time to receive professional treatment.