Hair is a characteristic outgrowth of the outer skin layer, or epidermis, in many mammals. It serves various functions for some animals, including thermal regulation, camouflage and communication (for example, polar bears’ transparent fur gives them camouflage and helps regulate body heat). It may also serve as a signal for mating or warning others of danger, or act as a defence by causing a repellent response from predators. It can be a major part of one’s appearance, and the choice of hair style, colour and length may have social significance. For many people, it is a source of pride and identity.
Hair is made up of a protein called keratin. It forms a protective, tough external covering that covers the inner core of the hair follicle, which is filled with blood. Hair follicles produce hair in three distinct phases. The first, the catagen phase, lasts two to four weeks and is followed by a resting phase, or telogen phase, that can last several months. During this time, the supply of blood to the follicle is cut off. At the end of this phase, the follicle becomes empty and the hair is gradually pushed out of the skin. New follicles then begin to grow at the site of an old follicle, starting the cycle all over again.
The most common type of hair is straight, which accounts for 80% of all human hair. Curly hair is less common, affecting 9% of all humans. Among non-human primates, body hair is generally straight and thin. Head hair, however, is generally wavy or curly. The elasticity of hair is determined by the structure of its cuticle and varies between individuals. Thin, fine hair tends to have a more flexible cuticle than thick, coarse hair.
A person’s hair can be influenced by genetics, the environment and other factors such as diet, exercise, stress and hormones. Hair can also be affected by aging, illness and certain medications.
It is important for authors to understand the different facets of hair so that they can effectively describe it in their writing. In addition to understanding the different textures, colours and lengths of hair, it is important to have a knowledge of how to cut and style it. Proper hair styling can accentuate good features and hide bad ones, or draw attention away from undesirable attributes.
A great resource to help writers describe the look and feel of a character’s hair is this post on WITS from a few years ago. It is still very relevant today and can help writers create realistic, believable descriptions of someone’s hair.