There is a piece of foreskin like sandpaper, common causes are sebaceous ectasia, phimosis, pearly papules, eczema and other causes. 1. sebaceous ectasia: the etiology is unknown, may be related to genetic factors, endocrine factors local stimulation, may cause the local mucous membrane with small yellowish pimples, size similar to the size of a pinhead, slightly protruding from the skin of the flat pimples, may lead to the appearance of a small particle on the foreskin. 2. circumcision: the external infection of various pathogenic bacteria, may cause inflammatory reaction of the foreskin, resulting in prominent skin pimples, manifested as small particles on the foreskin. It is easier to appear when the foreskin is too long. 3. Pearl-like pimples: the etiology is unknown, may be related to long-term stimulation, the typical performance will lead to the edge of the glans coronal groove, there are pearl-like small particles, may also cause pearl-like pimples on the foreskin. 4. Eczema: Inflammatory skin reactions caused by a variety of internal and external factors, can cause the skin to have a rash, itching, accompanied by a tendency to ooze in the acute phase, may also lead to the appearance of small granules on the foreskin. Small particles on the foreskin, there are other causes such as dermatophytes, it is recommended to go to the hospital in time for examination and treatment as prescribed by the doctor.