Why does scrotum turn black?

Hu Hai: Scrotal skin is very sensitive to external temperature. When swimming, the water temperature is much lower than the body temperature, which stimulates the contraction of the smooth muscle of the meat membrane and the levator testis, makes the position of the testis rise, tightens the scrotum skin into dense folds, retracts to the perineum, prevents heat dissipation and helps to keep warm. The same phenomenon will happen when the wind is cold. On the contrary, when the external temperature rises, the smooth muscle and cremaster muscle relax, the testis descends, and the scrotal skin relaxes in vitro, which increases the heat dissipation area and is beneficial to local heat dissipation.

%3; & 9 \, Mu Bai Medicine

As for the scrotal skin color black, it is affected by sex hormones. Originally, people's skin color depends on various pigments.

Especially the amount of melanin, the thickness of skin and the contraction or relaxation state of blood vessels. An important factor affecting melanosis cutis is sex hormones. The concentration of sex hormones in sexual organs and other parts is high. As a result of long-term hormone stimulation, a large amount of melanin is deposited and the skin color becomes darker, especially after contraction and thickening. In the same way, you may have noticed that the nipples and areola around adult men are also quite black! The little boy's sex hormone level is very low, so his skin color has not changed much. The scrotum is similar to the surrounding skin color, and this pigmentation change will only appear after puberty.