Unterhaar

Unterhaar is the soft, dense layer of fur closest to the skin in many mammals that have a double coat. It lies beneath the longer, coarser guard hairs (often referred to in German as Oberhaar or Deckhaar). The Unterhaar consists of short, fine hairs that trap air and provide insulation, helping to keep the animal warm in cold weather and to regulate moisture near the skin. The thickness and length of the Unterhaar vary with breed, season, climate, age, and health.

The Unterhaar plays a key role in temperature regulation. In cold climates it tends to be fuller to maximize insulation, while in warmer conditions it may be reduced as part of seasonal shedding. During the hair cycle, animals shed old underfur and grow new underfur in a process called molting. Regular grooming helps remove loose underfur, reduce matting, and improve comfort. Special tools such as undercoat rakes or deshedding brushes are commonly used for this purpose. An excessively thick or poorly shed Unterhaar can contribute to overheating in hot weather or trap moisture if not managed.

Examples of animals with a pronounced Unterhaar include many double-coated dog breeds such as the German Shepherd, Siberian Husky, Alaskan Malamute, Chow Chow, and Akita, as well as numerous cats and rabbits. In German, Unterhaar is sometimes referred to as Unterwolle or Unterfell, and is distinguished from the outer guard hairs.