Dirt at the penile coronal sulcus is mainly related to the local anatomy, where it is easy to hide dirt, such as the presence of circumcision, phimosis, etc., which is more likely to lead to the accumulation of dirt. The coronal sulcus is a ring of grooves at the lower edge of the glans penis in men. Turning the foreskin over, you can find a ring of narrowing behind the glans called the coronal sulcus. Urethral spongy body anterior expansion into the glans, formed at the base of the glans, is the sensitive part of the penis, normal red slightly purple. Here because of the special anatomical reasons, local secretions, urine, shed dander, dust and other easy to accumulate in the formation of dirt. This phenomenon will be even more serious if there is a case of circumcision or phimosis. The glans and the coronal sulcus should be thoroughly cleaned with running water every day to avoid the formation of dirt. If the foreskin is not turned out thoroughly enough due to the long foreskin or phimosis, it is relatively difficult to clean and cause local inflammation, it is recommended to perform circumcision in time. If the patient is not feeling well, he should consult the doctor for examination and early treatment.