The dark corners of the mouth are usually can be applied topically Vitamin A acid cream. 1. Vitamin A cream is a derivative of vitamin A, usually can promote epidermal metabolism, reduce skin pigmentation, promote the renewal of epidermal cells, regulate the proliferation and differentiation of epidermal cells, so that the cells of the stratum corneum become loose, easy to fall off. Therefore, the black corners of the mouth can be externally applied retinoic acid cream, which has a certain effect. 2. External use of this product may cause skin irritation, burning sensation, erythema and flaking and other adverse reactions. The irritation may disappear gradually after adaptation and tolerance. If the irritation persists or worsens, the drug may be used intermittently or suspended under the supervision of a physician. Keep away from the eyes and protect the skin from the sun. It is contraindicated in patients who are allergic to retinoic acid cream and breastfeeding women. It is recommended that patients use the drug properly under the guidance of a doctor, and not blindly use the drug on their own.