four reasons for ... MEN NOT TO WEAR TIGHT UNDERWEAR.
1 IT MAKES YOU STERILE BELIEVE it or not, there's a good reason why the testicles are kept outside the body rather than being tucked up inside. Sperm needs to be kept at a fairly stable temperature, around 36C, and the body is able to automatically adjust the temperature by keeping them closer or farther away from the body.
2 IT REDUCES TESTOSTERONE ANOTHER side effect, related to overheating, is testosterone reduction. Testosterone is the essential male hormone, and having less of it will lead to lethargy, weaker muscles and general malaise.
3 IT CAN CAUSE TESTICULAR TORSION TESTICULAR torsion is a condition where the testicles become twisted internally. It's extremely painful, surprisingly common and can lead to the testicle becoming gangrenous and being removed.
4 IT CAN LEAD TO RASHES TIGHT underwear tends to become moist and this can lead to itchy, irritated skin. This environment is also ripe for infection, so there is a much bigger risk of a fungus developing.