Polypropylene underwear is a type of base layer of clothing. It is the closest layer of clothing to the skin, and it is intended to wick moisture away from the skin to keep the body dry and comfortable, especially during athletic activities. Polypropylene underwear is commonly used by athletes who participate in cold weather sports; this is because the athlete needs moisture wicked away from the skin to keep it warm and dry during inclement weather. It can be used during warm weather activities as well, and polypropylene — or polypro — is usually lightweight enough for a variety of athletic activities.
One of the biggest advantages of polypropylene underwear is its ability to transfer moisture easily and quickly. When sweat sits on the surface of the skin, the body's temperature can become more difficult to regulate, and chafing may occur when skin comes in contact with other skin or with fabrics such as shirts and pants. Polypropylene underwear prevents the sweat from staying on the surface of the skin, thereby keeping the skin dry and cool in the summer and warm in the winter. The less sweat present on the skin means less potential for chafing or other types of discomfort. Polypro is also quick-drying, so athletes using the polypro for long periods of time will remain comfortable longer.
Another distinct advantage of polypropylene underwear is its light weight and easy packability. Athletes prefer the light weight because it means the underwear will not interfere in any way with the normal functions of the limbs or the rest of the body, and it will be more comfortable. Backpackers and other recreational users will appreciate the light weight of the polypro should they have a need to pack or store it while carrying a backpack. During cold weather trips, several sets of polypro underwear can be packed with a minimal weight penalty.
One major disadvantage of polypropylene underwear is its ability to retain odors. As sweat seeps into the material, the body odors can become trapped there, even after frequent washing. Polypropylene underwear is especially prone to such odors, since some of the sweatiest parts of the body will come in contact with the underwear. For athletes, this is not too significant of a problem, but for people wearing the polypro underwear underneath work or casual clothing, the odor can be problematic. More recent versions of polyester clothing wick moisture almost as effectively as polypro without the odor issues coming into play.