Seborrheic alopecia is also called sex hormone-derived alopecia or male pattern baldness. The etiology of this kind of hair loss is related to the metabolism of androgens, androgens (testosterone) are converted into dihydrotestosterone under the action of 5a-reductase, which is the number one killer of hair follicles and can produce toxic effects on hair follicles, causing them to atrophy, and the hairs gradually become thinner, shorter and lighter in color, and finally become similar to sweat hairs and cannot effectively The hair follicles atrophy, the hair gradually becomes thinner, shorter and lighter in color, and finally becomes similar to sweat hair and cannot effectively cover the scalp, forming hair loss. Most of the hair follicles in the alopecia area do not disappear and can produce normal hair after timely and appropriate treatment. The key to treatment is to inhibit 5a-reductase and reduce the production of dihydrotestosterone so that hair loss is reduced and regrowth can occur. Previously, there was a misunderstanding about the cause of androgenic alopecia, believing that hair loss was caused by the oiliness of the scalp, which blocked the pores and affected the nutrient supply of the hair follicles, but the treatment of inhibiting scalp oil overflow did not improve the hair loss, causing many patients to spend a lot of money and time and delaying the treatment. Why does hair loss occur on the forehead, top of the head and the back of the head above the occipital area? The genetic characteristics of hair follicles in these areas are different, and they are very resistant to dihydrotestosterone. This is why the hairline is receding or Mediterranean hair loss is formed.