Underull

Underull is a base layer garment worn next to the skin, commonly used in Nordic countries and outdoor sports. The term denotes a woolen undergarment designed to provide insulation while managing moisture, functioning as the first layer in a layering system for cold or active conditions.

Historically, underull is made of wool, especially merino wool for its softness and temperature regulation. Modern versions may use blends with synthetic fibers such as polypropylene, polyester, or elastane to improve stretch, durability, and faster drying.

Underull tops and bottoms come in different weights: lightweight, midweight, and heavyweight. They may be seamless or feature flatlock seams, ribbed cuffs, and a crew or scoop neck. Some designs use two-layer or brushed surfaces on the inside to boost insulation.

Care instructions vary by fiber, but wool underull generally benefits from washing in cool water with a mild detergent and air drying; some merino fabrics can be machine washed on gentle cycles. Avoid high heat, fabric softeners, and fabric dryer to preserve moisture-wicking properties. They are used as base layers for activities such as hiking, skiing, snowboarding, and cold-weather work, under additional garments.

In Scandinavia, underull is a standard component of outdoor attire, valued for its warmth-to-weight ratio and ability to stay dry during activity. It also serves as a comfortable everyday layer in cold homes or climates.