Small black pimples on the foreskin can be caused by excessive friction, circumcision, infections and other factors. 1. Excessive friction: frequent sex or frequent masturbation can lead to excessive friction of the foreskin, but also can lead to the foreskin, glans and penis and other parts of the infection, can be localized in the black pigmentation, the appearance of small black pimples like performance. 2. Circumcision: the external stimulation of autoimmune system overreaction can be triggered by circumcision, the main manifestation of the mucous membrane of the foreskin edema, erosion and ulceration, can also be localized in the appearance of small black acne-like changes. 3. Sexually transmitted diseases: after infection of sexually transmitted diseases, the foreskin can appear hyperplasia, pimples, ulcers and other manifestations, localized small black pimple-like manifestations, in addition to chills, fever, loss of appetite and other systemic manifestations. When the foreskin has a small black pimples should be timely medical treatment, under the guidance of a specialist doctor active treatment, help early relief of uncomfortable symptoms.