Abstract:

Non-physiological alopecia refers to a phenomenon that severely affects the appearance of patients, such as a heavy loss of hair leading to thinning hair or receding hairline. According to the different causes, it can be categorized into androgenic alopecia （AGA）, immunodeficiency alopecia （IDA）, skin damage alopecia （SDA）, nutritional abnormalities alopecia （NAA） and drug-induced alopecia （DIA）. All these types of hair loss are caused by corresponding factors that directly or indirectly act on hair follicles. Among them, the pathological processes of AGA and IDA have been reported a lot. As for AGA, hair follicles are sensitive to androgens, leading to disorder of growth cycle; as for IDA, the breakdown of hair follicle immune pardon mechanism makes immune cells attack hair follicles. The reasons for SDA and NAA are relatively straightforward. They are caused by skin damage and nutrient deficiency, respectively, which lead to disorder of the physiological cycle of hair follicles and affect hair growth. There are many factors influencing DIA, which vary according to different drugs. Herein, the mechanisms of non-physiological alopecia caused by various reasons have been briefly described. Research results of non-physiological alopecia are focused on. It may provide a better understanding of the causes and mechanisms of non-physiological alopecia, which might help researchers to find a way to prevent hair loss.

Key words: alopecia, androgen alopecia, mechanism, progress