The main problem is that there is a chain reaction between dry skin and hyperactive sebaceous secretion. In detail, the main function of sebum secretion is to moisturize the skin. When the skin is deprived of moisture, the sebaceous glands receive the “signal to increase secretion” and then some of their functions are hyperactive. If Propionibacterium acnes is also present, moderate to severe acne is likely to occur, and cystic acne is inevitable. In the fall and winter, the dry and cold climate in northern areas is the main cause of acne. A history of acne for many years and the lack of timely removal of Propionibacterium acnes are the main internal causes. Treatment ideas: Along with internal medication, acne treatment is recommended for the skin level. 1, sebaceous gland function regulation treatment to reduce oil secretion. 2, skin hydration import treatment, remove dehydration factors, assist the use of medical grade hydration oil control daily chemical products. 3.For the nodules that have already formed: using high energy blue light to eliminate Propionibacterium acnes is the first step, photothermal anti-inflammatory, shrink the treatment nodules is the key.