Retinoic acid can be used as an adjuvant therapy for psoriasis (psoriasis) and can also be used to treat multiple vulgaris and various skin diseases such as ichthyosis and keratosis follicularis. Retinoic acid could be used for abnormal acne, fish phosphorus disease and abnormal psoriasis. Retinoic acid is also known as vitamin for-mic acid and retinoic acid, this strain is the metabolic intermediate product of vitamin A in the body, which mainly affects the growth of bone and the metabolism of epithelial cells and has the effects of promoting epithelial cell proliferation and keratolysis. It is suitable for acne vulgaris, lichen planus (including oral lichen planus), leukoplakia, pityriasis red hair and pityriasis simplex on the face, etc.