Why Wicking Underwear Beats Cotton

Wicking underwear:

  • Efficiently transports perspiration away from skin.
  • Dries much faster than conventional cotton underwear.
  • Reduces the risk of dramatic swings in body temperature.

In very windy or extremely cold conditions, such advantages are potentially life-saving.

Base Layers



This refers principally to polyester and polyester blends. Some underwear blends use high percentages of nylon (as a means of increasing abrasion resistance), or they add small amounts of spandex or elastin (to enhance stretch). Polyester, though, is the dominant synthetic fibre used in wicking first layers. It’s a soft, easy-care fabric with reliable moisture-management attributes.

Additional pros:

  • Lightest in this group.
  • Abrasion-resistant.
  • Wrinkle-resistant.
  • Easy care.

Additional cons:

  • Odours may build if worn repeatedly on multiday outings.
  • Potentially vulnerable to staining.
  • Petroleum-based fibre.


This almost always refers to merino wool, which is popular due to its soft “ultrafine” fibres. Many people are surprised to learn that lightweight (even “micro weight”) merino wool creates a terrific all-season base layer.

Additional pros:

  • Lightweight merino wool is soft on skin.
  • Usually machine-washable.
  • Stain- and wrinkle-resistant.
  • Natural fibre with a high comfort factor

Additional cons:

  • Typically available only in darker colours.
  • Potentially vulnerable to shrinkage.

What is Merino Wool?

Full wool Merino sheep.
Full wool Merino sheep. (Photo credit: Wikipedia)

The source of merino wool is merino sheep, a breed that originated centuries ago in Spain. (The word “merino” has Spanish roots.)

Merino sheep were introduced to Australia in 1794, and they flourished in the island nation’s temperate interior. Today the majority of merino sheep are raised in New Zealand (at high elevations), Australia, South Africa and South America where the climates and the vegetation consumed by sheep contribute to the exceptional quality of merino wool. It is estimated that 1 square inch of skin on a merino sheep produces roughly 4 times the number of fibres than other breeds.

As mentioned earlier, merino wool fibres range between 15 to 24 microns in diameter, with 17.5-micron fibres (rated “ultrafine”) often used for next-to-skin apparel. The merino industry regards 18.5 microns as the average fibre diameter most people can wear without experiencing an itchy sensation.

In comparison, human hair ranges between 18 and 180 microns, with an average diameter of about 60 microns. Only the wispiest, most flaxen human hair comes close to approximating the diameter of merino wool.

The abundant crimps in merino wool fibres permits the spinning of high bulk, resilient yarns, which can then be knitted or woven into structures tailored to particular end uses. For outdoor apparel and socks, knits are the most common structures.


Silk (Treated Silk)

Silk underwear is largely a specialty fabric, intended primarily for cool- and cold-weather usage. “Treated” indicates the silk has been chemically modified to enhance wicking (a fabric’s capacity for moving perspiration off skin to speed its evaporation). Fans of silk are strongly attracted to its smooth texture.

Additional pros:

  • Soft, luxurious texture.
  • Thin; adds no bulk and layers well.
  • Natural fibre.

Additional cons:

  • Some styles require hand-washing; machine washing sometimes causes shrinkage.
  • Potentially vulnerable to abrasion and sunlight.
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