Most men do not think about whether the underwear they wear affects their sexual health. Most often, they buy underwear that they are used to, regardless of its type or composition. Briefs fit better on the body, especially with a well-maintained body physique, and do not create problems when walking, like boxers, whose short legs often “roll” to the pelvis and create discomfort. Briefs also keep a man’s anatomy in one position, even during sports activities, and are associated with a lower likelihood of testicular torsion – a painful and dangerous twisting of the testicle that results in twisting of the vas deferens. Boxers are more comfortable, they are also suitable for fuller men, they have more space for maneuvering, sweating is more tolerable and above all: they do not press the testicles to the body. This is an important advantage, because spermatogenesis – the formation of new sperm in the testicles – is strongly affected by temperature. It should be a few degrees lower than the general body temperature. A higher temperature slows spermatogenesis, and the closer the testicles are to the skin, the more heat they absorb from the tissues of the pelvis and thighs. Enclosing them in underwear and pants further increases the degrees, which affects the testicular tissues and spermatogenesis and lowers male fertility. NEWS_MORE_BOX This is an especially important issue because over 50% of cases of problems conceiving in married couples come from low sperm count – a condition known as oligospermia. The fabrics from which the underwear is made are also important: cotton is universal; linens are stronger and more thermally conductive, making them excellent for hot weather; fabrics made of wool and silk threads are less thermally conductive and are suitable for colder weather; underwear suitable for sports activities may contain nylon threads, but the material is not breathable and should not be worn for long periods of time; polyester fabrics are the most harmful for long-term use – steamy, insulating material that predisposes to the development of bacteria, strong odor and can lead to rashes and infections. It is advised to avoid underwear containing antibacterial materials, unless recommended by a doctor. Although effective, there is no scientific evidence for the biosafety or lack of interaction between silver ions, on which the antibacterial properties of the tissues and the health of the testicles and the sperm produced in them are based.