With the substantial improvement of the quality of life, people have higher requirements for eating, drinking and wearing, however, many people easily neglect their underwear. In life, people do not have much demand for underwear, as long as comfortable, but do not know that tight underwear has become a new sperm killer, is one of the factors that constitute male infertility. Sperm survival time is different at different temperatures The male sex organ scrotum is wrapped around the testicles, which are the place where sperm are produced, and it can be seen that the most suitable temperature for sperm to survive is the temperature of the human body, i.e. 36.0℃-37℃. It is understood that the spermatozoa in the 37 ℃ environment in the activity of survival time in more than 4-8 hours; in the vagina activity survival time of 0.5 days; in the cervix in the activity of survival time of 2-8 days, in the uterus and fallopian tubes in the activity of survival time is 2-2.5 days. It can be seen that the survival time of sperm is directly affected by temperature, the higher the temperature, the faster the sperm die. Underwear can dramatically increase testicular temperature and kill sperm Both the testicles producing sperm in the scrotum and the sperm surviving in the body are affected by temperature. It is for this reason that on hot summer days, the scrotum loosens up; when it’s cold, it tightens up into a crumpled little mass that clings to the body and regulates itself as the temperature changes. However, this balance is disrupted by tight underwear, which wraps the scrotum tightly and puts it in a closed state, with no air circulation, preventing the skin of the scrotum from dissipating heat and cooling down, thus affecting the physiological function of the testicles, which may produce abnormal sperm, or even not be able to produce sperm. At the same time, tight underwear restricts blood circulation and hinders the return of the spermatic vein, which is unfavorable to sperm production and nutrition, and in the long run, it is easy to cause the adverse consequences of infertility in the future. It is worth noting that the choice of underwear is also different depending on individual circumstances, such as for men who sweat a lot, cotton may not be the best choice. Because cotton underwear although absorb sweat, but not easy to dry, especially in summer, the sticky feeling of the pubic area is not only uncomfortable, but also may cause scrotum inflammation, bring itching and tingling of the reproductive system diseases. Therefore, men’s choice of underwear is not the slightest bit sloppy, comfortable and appropriate is the focus.