The black spot on the male foreskin is not necessarily caused by disease, but after all, not quite normal or need to pay enough attention to. The general cause of the black spot on the foreskin is mainly due to several aspects: first, frequent masturbation caused by the. Frequent masturbation can increase the chances of infection of the penis and glans. The frequent rubbing of the foreskin during masturbation also tends to cause accelerated melanin deposition in the foreskin area. Second, foreskin glansitis. The inflammation can stimulate the foreskin causing the local skin to break down and then easily leave a black spot. The third, unclean sex later caused by STD infection. Most STD infections mainly invade the reproductive system, especially the penis, foreskin, glans and other parts. Even if cured there will always be some problems left behind, the appearance of black spots on the foreskin is also very common. Fourth, the normal precipitation of melanin, foreskin for a long time by the influence of underwear friction may also appear in the foreskin area black spots. These are the main factors for the appearance of black spots on the foreskin area.