The testicles are always cold when touched because they have the function of self-regulation of temperature, which is done through the stretching and contraction of the scrotal skin. The temperature of the normal scrotal cavity is slightly lower than the body temperature by about 1-2°C to maintain the normal spermatogenic function and to ensure that the testicular spermatogenic tubules work normally, so the temperature in the scrotal cavity is slightly lower than the body temperature by 1-2°C, which is cold to the touch. It does this by contracting and stretching the scrotal skin. When the external environment is warmer, the skin of the scrotum will stretch, and then the testicles will move away from the body, causing the temperature inside them to drop. When the outside temperature is colder, the scrotal skin contracts and the testicles come close to the body to keep the temperature of the scrotal cavity not slightly lower, so it is a normal physiological phenomenon to feel the scrotum slightly colder than your body temperature when you touch it.