Ulcers on the left side of the tongue are a clinical symptom of the oral mucosa, for which there are generally 3 conditions that are more common in clinical practice. The first is the most common what we normally call oral ulcers, located just to the left of the tongue. This ulcer is also called recurrent oral ulcer, oral aphthous ulcer, which is typically characterized by significant pain and can be self-limiting and recurrent. These ulcers usually heal spontaneously without special intervention in about a week to 2 weeks. However, these ulcers are also difficult to eradicate and often reoccur in other areas. Another common type of ulcer is the traumatic ulcer, which is on the left side of the tongue and is usually associated with a sharp tooth tip on the lingual side of the tooth. This type of ulcer has a relatively long duration and is slow to improve because of the irritation of the tip of the tooth. Also, if this ulcer persists for a long time, it may become the third type of ulcer – cancerous ulcer. Cancerous ulcer means that the ulcer itself has undergone pathological changes and appears in the state of malignant tumor, at which time 1 must consult a doctor as soon as possible and treat it for oral cancer.