[Medical Q&A] How does smegma form in little boys and what health problems may it cause?

Planner: Chinese Medical Association

Reviewer: Deng Chunhua, Chief Physician, First Affiliated Hospital of Sun Yat-sen University

Just as the skin on other parts of the body secretes sebum, the sebaceous glands of the foreskin also secrete sebum. When phimosis or prepuce is too long, the foreskin cannot be turned over for cleaning, and sebum will accumulate in the gap between the inner surface of the foreskin and the glans penis. In addition, urine will also seep into this gap and react chemically with the sebum to form smegma and produce odor. Smegma that accumulates for a long time will become a hard, lumpy substance similar to bean dregs. Smegma is more common in childhood, and its main causes are phimosis and prepuce that are too long, which make it impossible to thoroughly clean the inner surface of the foreskin and the glans penis, thus forming smegma. Adults generally do not have phimosis, and even if they have a long foreskin, smegma will usually not form as long as they maintain good cleaning habits.

Smegma can irritate the foreskin and glans penis, causing chronic inflammation. If acute infection occurs, it can cause redness, swelling, and pus discharge from the foreskin and glans penis. The long-term presence of smegma may also increase the risk of penile cancer. Therefore, it is recommended to remove smegma regularly to keep the reproductive organs clean and hygienic.