Small pimples on the chin can be caused by acne, folliculitis, seborrheic dermatitis and other factors. 1. Acne is a common chronic inflammatory disease of the sebaceous glands of the hair follicles, mainly caused by abnormal levels of androgens, blockage of hair follicles, and propagation of Propionibacterium acnes, which can lead to localized whiteheads, blackheads, pimples, and nodules on the skin. 2. Folliculitis: it is an inflammatory skin disease of hair follicles, which can occur in any part of the hair follicles, leading to red papules around the hair follicles, and sometimes there can be pus, itching, pain and other discomforts. So when folliculitis occurs in the skin of chin area, small pimples can also appear. 3. Seborrheic dermatitis: also known as seborrheic eczema, is a common chronic superficial inflammatory skin disease, usually caused by Malassezia infection, sebum level abnormalities and other factors. It can lead to localized skin erythema, pimples, itching and other uncomfortable symptoms, so the presence of seborrheic dermatitis on the chin, can also grow small acne. There are many reasons for chin smallpox, it is recommended to go to the hospital in time, improve the examination and clear diagnosis, under the guidance of the doctor for the cause of reasonable treatment.