Acne vulgaris, commonly known as acne, is an inflammatory skin disease that occurs in the sebaceous glands of hair follicles. Most acne occurs around the age of adolescence (14-20 years old), but there are cases of earlier onset (e.g., around age 10) and later onset (e.g., after age 40). The lesions appear on the cheeks, forehead and nose, followed by the anterior chest, back and shoulders. There are two main types of clinical manifestations: non-inflammatory lesions and inflammatory lesions. Non-inflammatory lesions are blackheads and whiteheads. Inflammatory lesions have a variety of manifestations: papules, pustules, nodules, and cysts. Inflammatory acne can leave marks after healing in mild cases or scars in severe cases. There are two types of marks left by acne, one is a red mark, which occurs mostly in the early stages. The other is pigmentation, which occurs in the late stage. There are also two types of scars left by acne, one is depressed scars and the other is hyperplastic scars. These scars and hyperpigmentation are both temporary and permanent. Their presence affects beauty and has a psychological impact. How to prevent it? 1, actively treat acne, do not wait for a lot of growth and very serious. To treat early can reduce scarring and pigmentation. 2. Do not squeeze, press or pick at the skin lesions. Avoid aggravating the local inflammatory reaction. 3. Avoid sunlight exposure in the early stage of skin lesion decrusting. To prevent aggravation of hyperpigmentation, topical sunscreen can be used. 4. Pay attention to facial skin cleanliness to prevent repeated infection. How to treat the scar of acne? The treatment plan should be made according to the scar situation. In the early stage (within 3-4 months), it is not necessary to actively treat the scar, because the scar has the possibility of natural fading. Measures can be taken if the scar does not fade beyond 3-4 months. For depressed scars, liquid crystal grinding treatment is available. For mild hyperplastic scars, topical medications such as scar enemy, Xylactol, and spiritus can be used. For severe cases, freezing, surgery or radiotherapy can be considered. How to treat hyperpigmentation of acne? The pigmentation is due to the inflammation process, the dead inflammatory cells are phagocytosed and deposited in the local area. The hyperpigmentation is resolved by phagocytes moving the dead inflammatory cells away. This process is slow, usually 2 to 3 months, and light cases can be treated without treatment, waiting for natural fading. For severe cases, topical hydroquinone cream, azelaic acid cream, Xylactol, tretinoin cream, retinoic acid cream, etc. can be used.