Hair

Hair is a filamentous outgrowth of protein, found only on mammals. It projects from the epidermis, though it grows from hair follicles deep in the dermis. Although many other organisms, especially insects, show filamentous outgrowths, these are not considered "hair". So-called "hairs" (trichomes) are also found on plants. The projections on arthropods, such as insects and spiders are actually insect bristles. The hair of non-human mammal species is commonly referred to as fur. There are varieties of cats, dogs, and mice bred to have little or no visible fur. In some species, hair is absent at certain stages of life.

The primary component of hair fiber is keratin. Keratins are proteins, long chains (polymers) of amino acids.

Demodex is a genus of tiny parasitic mites which live in or near hair follicles of mammals.