Cracks at the corners of the mouth may be caused by dehydration, malnutrition, microbial infections, and xerostomia. 1. Dehydration: If you don’t drink enough water in your life, and there is severe dehydration, it will lead to cracks at the corners of the mouth, and you need to replenish more water, so that there is enough water in the cells of the organism. 2. Nutritional deficiencies: If you are undernourished and lack vitamin B, it can lead to the appearance of cracks at the corners of the mouth. 3. Microbial infection: when infected by bacteria, viruses, fungi and other microorganisms, it will lead to cracks at the corners of the mouth. 4. Keratitis: this disease is mainly affected by pathogen infection, trauma, malnutrition, abnormal immune function, physical stimulation and other factors, the appearance of cracks at the corners of the mouth, accompanied by swelling, pain and other symptoms. If the symptoms continue to develop, you need to go to the hospital in a timely manner, actively cooperate with the treatment, pay attention to drink more water, do not eat spicy and irritating food, and avoid large-scale open-mouth action.