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The Ultimate Guide to Long Underwear: What You Need To Know

The Ultimate Guide to Long Underwear: What You Need To Know

Staying warm during colder months requires a must-have clothing item - long underwear. With so many options available, it can be challenging to choose the right one, so we've created the ultimate guide to help you find the best long underwear for you. Discover everything you need to know about this essential winter clothing item and stay warm and cozy throughout the cold season.


What is Long Underwear?

Long underwear, also known as thermal underwear or base layers, is a specialized garment designed to provide essential insulation and moisture management in cold weather. It is worn beneath regular clothing as a protective layer, helping to retain body heat while effectively controlling moisture.

Long underwear is a winter essential, and the choice of materials plays a significant role in its performance. Synthetic materials like polyester and nylon offer moisture-wicking properties that draw sweat away from the skin, keeping you dry and preventing discomfort.

On the other hand, natural fibers like merino wool offer exceptional insulation, regulate body temperature and resist odor, making them ideal for outdoor activities. Merino wool, derived from merino sheep, is highly sought-after for its insulating properties and ability to regulate body temperature. Its unique structure traps air within its fibers, providing excellent insulation and retaining body heat, even when wet. It's also soft, lightweight, and breathable, making it ideal for outdoor enthusiasts. It is also naturally odor-resistant, thanks to its antibacterial properties, allowing you to wear clothes and long underwear for extended periods without worrying about unpleasant smells. 

When selecting long underwear, it's essential to consider the specific conditions and activities you'll be undertaking. 

Types of Long Underwear:

There are two types of long underwear: lightweight and heavyweight. Lightweight long underwear is suitable for milder weather or as a base layer for everyday use, providing a comfortable layer of insulation. Heavyweight long underwear is designed for extreme cold weather conditions and high-intensity activities such as skiing, snowboarding, hiking, mountain climbing, or ice fishing.

Material Types:

As mentioned earlier, long underwear can be made from various materials. Here are some of the most popular ones:

  1. Polyester: Polyester is a synthetic material that is excellent for moisture-wicking and quick drying. It is also durable and affordable.
  2. Nylon: Nylon is another synthetic material that is strong, lightweight, and abrasion-resistant, and it is also quick-drying and moisture-wicking.
  3. Merino Wool: Merino wool is a natural fiber that is soft, comfortable, and has excellent insulation properties. It also wicks moisture away from the skin, keeping you dry and warm.
  4. Silk: Silk is a luxurious natural fiber that is lightweight and breathable. It is an excellent choice for layering for people with sensitive skin.
  5. Cotton: Cotton is a natural fiber that is soft and comfortable. However, it is not a good choice for long underwear as it retains moisture, making it unsuitable for cold weather activities.


To ensure optimal insulation and comfort, it is crucial to select the right size of long underwear. The ideal fit should be snug enough to provide warmth but not too tight to restrict movement. Long underwear that is too loose may fail to trap heat effectively, while overly tight long johns may constrict movement and cause discomfort. Strive to find the perfect balance between comfort and insulation to make the most of your long underwear during cold weather activities.


Finding the right fit is crucial when choosing long underwear, as it directly affects comfort, mobility, and the effectiveness of insulation. Long underwear that is too tight can restrict movement and hinder circulation, while long underwear that is too loose may not provide adequate insulation or moisture-wicking capabilities. Here's a closer look at why finding the same style and proper fit is essential:

Comfort: Long underwear should provide a comfortable base layer that you can wear throughout the day without discomfort. A proper fit ensures that the fabric sits smoothly against your skin, avoiding any chafing or irritation. It should feel snug but not constricting, allowing you to move your arms and legs freely and comfortably.

Insulation: Long underwear acts as a thermal barrier, trapping a layer of warm air close to your body. For optimal insulation, the long underwear should fit snugly against your skin. This snug fit helps to minimize air gaps between your body and the fabric, reducing heat loss and maximizing the garment's insulating properties.

Moisture Management: Long underwear plays a crucial role in moisture-wicking, drawing sweat away from your skin and allowing it to evaporate. A proper fit ensures that the fabric remains in close contact with your skin, promoting efficient moisture transfer. If wearing the long underwear is too loose, sweat may become trapped, leading to dampness and potential discomfort.

Layering: Long underwear is typically worn as a base layer, providing a foundation for layering additional clothing. A proper fit ensures that the long underwear sits close to your body, allowing for easy layering of mid-layers, jeans, and outerwear without unnecessary bulkiness or constriction. It should provide a smooth and seamless foundation for your overall clothing system.

Care and Maintenance

Alt Text: clothesline with clothespins

To ensure that your pair of long underwear lasts for years, it's essential to take care of them correctly. Here are some tips for caring for your two pairs of long underwear:

  1. Wash your long underwear in cold water and on a gentle cycle.
  2. Do not use fabric softener or bleach as they can damage the fibers.
  3. Hang your long underwear to dry, as the high heat from the dryer can damage the fibers.
  4. Avoid using harsh detergents as they can strip the fibers of their moisture-wicking properties.


Long underwear is an essential item for anyone looking to stay warm, cozy, and dry during cold weather activities. Choosing the right type of long underwear, material, fit, and layering techniques can make all the difference in keeping you comfortable and protected from the elements. With the tips provided in this ultimate guide, you can confidently choose the perfect long underwear.

Stay warm and comfortable in the cold with Undersummers' high-quality long underwear. Our anti-chafing undergarments ensure maximum insulation and moisture-wicking capabilities, while our proper fit guarantees comfort and mobility. Don't let the cold stop you - shop now at Undersummers for the perfect long underwear to keep you cozy this winter.
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Meet our founder: CarrieRae

Undersummers Shortlettes were created CarrieRae's personal need for comfortable thigh protection when she was working as a teacher. In 2011, her thick thighs rubbed and she needed a comfortable solution.  Pants are blazing hot in the Houston spring/summer months, shorts are not acceptable to wear to work, so she was left with capris and dresses.  Her thighs did not support wearing dresses, thigh chafing was too uncomfortable.  The idea of wearing a breezy dress sounded so comfortable to her, that she created the solution to her problem:  The Original Lace Shortlette®️. She wanted something to wear that was a single layer, the legs stayed put, comfy, and most importantly, pretty.

CarrieRae Munson