Repeated acne is considered to be caused by changes in hormone levels, keratinization of the sebaceous gland ducts of the hair follicles, and the propagation of Propionibacterium acnes. 1. Hormone level change: After the human body enters puberty, the level of androgen in the body will increase significantly, which leads to an increase in the secretion of sebaceous glands, and the oil and keratin shed by the epidermis will block the hair follicles, resulting in recurrent acne. 2. Keratinization of follicular sebaceous gland ducts: the proliferation and hyperkeratinization of keratinocytes in the ducts of hair follicles block sebum excretion, which can lead to recurrent acne when sebum and keratin plugs accumulate in the mouth of hair follicles. 3. Propionibacterium acnes reproduction: The reproduction and growth of Propionibacterium acnes can induce an inflammatory reaction, which can lead to recurrent acne. Since there are many causes of recurrent acne, it is recommended to go to the hospital for examination and diagnosis, and then under the guidance of a professional doctor, carry out targeted treatment according to the individual’s situation, so as to avoid aggravating the symptoms of the disease.