What Is Long Underwear?

M.C. Huguelet

Long underwear is a type of garment worn beneath one’s clothes to protect the body from cold weather. Sometimes also referred to as long johns, it normally takes the shape of a shirt and legging-style pants, although some argue that one-piece undergarments can also be classified as long underwear. Long underwear has traditionally been made from natural fibers like cotton and wool. Late 20th-century advancements in textile technology have allowed for the creation of long underwear made from synthetic materials that offer excellent body temperature regulation.

Long underwear helps the body retain heat in cold temperatures.
Long underwear helps the body retain heat in cold temperatures.

Generally, long underwear is worn beneath the clothes to protect the body from cold weather. It can be worn by individuals in many different situations, such as those who work outdoors, those participating in a winter sport like skiing, or those who simply wish to keep warm while walking outside during the winter months. Despite its name, most people do not wear long underwear as a substitute for underpants. Rather, it is usually worn between the underpants and one’s outer shirt and pants.

Long underwear can be useful in winter sports like skiing.
Long underwear can be useful in winter sports like skiing.

To most people, these garments comprise a long-sleeved top and legging-style pants. While these two items are often sold as a set, they can be worn together or separately. This allows the wearer to decide which pieces he wishes to wear on a given day based on factors such as the weather conditions and the warmth of his outerwear. Some argue that the one-piece undergarment commonly known as a union suit can also be classified as long underwear. As a union suit does not feature separate top and bottom pieces, it does not afford the same level of body temperature control offered by long john sets, and is thus viewed by many as an inferior garment.

Traditionally, long underwear has been made from natural fibers like wool and cotton, often woven to create a “waffled” texture. While such materials are breathable, allowing air to circulate around the skin, they may require considerable drying time once they have been dampened by sweat or rain, thus compromising their ability to keep a wearer warm. Advancements in textile technology in the late 20th century have allowed for the production of heat-retaining undergarments made from synthetic materials such as polyester. These synthetic materials are designed to draw perspiration and moisture away from the skin and to dry quickly, thus allowing the wearer to remain warm in all kinds of winter weather.

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Discussion Comments


My husband works outside year round no matter how hot or cold it gets. In the winter he wears long underwear to work every day. He has tried almost every kind there is and seems to like the thermal underwear the best.

You would think with as many layers of clothing he wears, that there would not be much difference in the type of long underwear you wear, but according to him, there is. If your first layer does not keep you warm, the rest of your body will be cold and that pretty much defeats the whole purpose of wearing it.

With so many different kinds to choose from, it is not hard to find the fabric you like the best. I prefer something that is warm, but not bulky.


I always wear long underwear whenever I ski or snow mobile. I wear the long underwear as my base layer, and then add more layers on top of that. I used to wear cotton long underwear, but bought a pair of long underwear tops and bottoms at a ski shop that were called Chili's.

They are more of a polyester type of material and I like them much better. They are not nearly as bulky and seem to keep any moisture away much better. Once I started wearing them, I have never gone back to the cotton long underwear.

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