The patient suffers from angular cheilitis, which can cause local skin darkening. This condition is generally caused by repeated inflammatory irritation, leading to recurring stimulation of the local soft tissues and thus pigment deposition. At this time, it is advisable for the patient to maintain a light diet and refrain from too much worry. It could also be related to some hormonal imbalances, or digestive issues, accompanied by excessive infection of the follicular tissues, causing local soft tissue pigment deposition. At this time, it is suggested that the patient can locally apply some Vitamin E, which can help in the local repair. It is recommended for the patient to eat more fresh vegetables and fruits, and appropriately consume some Vitamin C. These can greatly help in enhancing resistance. (The use of medications should be carried out under the guidance of a professional doctor.)