Recurrent aphthous ulcers, also known as recurrent oral ulcers (commonly known as “mouth sores”), are the most common oral mucosal disease, with an average of one in five people having “mouth sores”, and can occur in both men and women, with young and middle-aged people being the most common. Recurrent aphthous ulcers are characterized by periodic recurrent attacks that can heal spontaneously and are not contagious. The ulcers can occur on any part of the oral mucosa, including the lips, cheeks, and tongue. There are three clinical types. In many patients, the ulcers increase in size and number as the disease progresses, with increased pain, longer healing periods and shorter intervals, affecting eating and speaking. Nevertheless, the disease is not cancerous. The causes of recurrent aphthous ulcers are not well understood, but the development is related to various factors, such as mental factors (fatigue, anxiety, stress), immune dysfunction, endocrine factors, genetic factors, etc. Although there are many treatments for recurrent aphthous ulcers, there is no cure for them. The main goal of treatment is to reduce pain and promote healing, or to prolong the interval between attacks. Treatment includes local and systemic therapy. Local treatment is mainly to achieve anti-inflammation, pain relief and promote ulcer healing. Systemic treatment can be done with herbal conditioning and appropriate application of immune agents to reduce the number of recurrences and other purposes. Since the disease cannot be completely controlled, prevention is especially important. Attention should be paid to keep the mouth clean, quit smoking and drinking, live a regular life and ensure sufficient sleep. Adhere to physical exercise, eat a light diet, eat more vegetables and fruits, eat less spicy, thick-tasting stimulating food, and keep the bowels unobstructed. Women should pay attention to rest before and after their periods, keep a happy mood, avoid excessive fatigue, eat a light diet, eat more fruits and fresh vegetables, drink more water, etc., to reduce the chances of ulcers. It is important to remind you that the ulcers that do not heal for a long time in the mouth, especially when there are residual roots, crowns, sharp tooth tips and other undesirable stimulating factors in the neighboring parts of the ulcers, should be given great attention, and if the stimulating factors are not removed in time, the ulcers will not only not heal, but will also get worse and may become cancerous. In conclusion, do not take it lightly and do not be overly nervous when you have a mouth ulcer, but go to a regular dental hospital or stomatology department for examination in time to get a clear diagnosis and timely treatment.