Cracking of the corners of the mouth is mainly seen in stomatitis, which is related to nutritional deficiencies, infections, traumas, allergies, environmental factors, and lifestyles. Cracking of the corners of the mouth is an inflammatory manifestation that occurs in the corners of the mouth area on both sides of the upper and lower lips, which can be unilateral or bilateral mouth cracking at the same time, commonly seen in patients with xerostomia, the main reasons are: 1. Nutritional deficiencies: can be caused by malnutrition, vitamin deficiencies, or secondary to diabetes mellitus, immune function abnormalities and other systemic diseases caused by cracked corners of the mouth. 2. Infection: if the abuse of antibacterial drugs and long-term use of antibacterial drugs for the treatment of diseases, it may cause oral flora imbalance, resulting in candida stomatitis and keratitis, causing cracking of the corners of the mouth. 3. Allergy: often occurring in allergic people, in contact with certain lipstick, ointment, cream and other cosmetics, as well as certain foods and medicines can trigger allergic cracking of the corners of the mouth. 4. Trauma: such as the use of rough instruments in oral treatment, excessive stretching of the corners of the mouth, etc., if not properly handled, secondary infection, may cause cracking of the corners of the mouth. 5. Environmental factors: high temperature in summer, dry air in fall and winter, the skin is easy to dry, the resistance of the external environment decreases, easy to crack the corners of the mouth. 6. Lifestyle: Frequent lip licking, smoking, drinking, betel nut chewing, eating a lot of spicy, fried food, etc. are likely to induce cracked corners of the mouth. Cracked corners of the mouth for a variety of reasons, if through the life of dietary adjustments do not improve, should promptly consult a doctor, under the guidance of the doctor for examination and treatment.