Hair Growth Cycle:
The Facts

Hair growth cycle The growth cycle originates from papillae cells at the base of follicles (pouches) within the skin. A follicle is about 4mm deep. (So, if a growing hair is plucked out, it will take more than a week to regrow and emerge from its follicle). The rate of hair growth is 3mm per week (faster than any other part of the body except bone marrow).

• The human hair growth cycle involves three stages - anagen, catagen and telogen:
• Anagen - the period of hair growth. Anagen lasts between three and five years (which means that, if left uncut, it will grow to between approximately 40cm and 70cm long).
• Catagen - the period of hair breakdown (which lasts just two weeks). The hair stops growing and detaches from the papillae cells.
• Telogen - the period of rest (which lasts three to four months). When telogen ends, anagen restarts.
• If you're in general good health, up to 90% of your scalp hair will be in anagen at any one time.
• The period of growth (anagen) and rest (telogen) varies from person to person, and is affected by diet, health and age.
• The hair growth cycle is independent for each hair - i.e., whilst many other animals have hair growth cycle synchronisation to some extent, we do not. (Cats, for example, moult heavily each spring, but we constantly lose between 100 and 200 hairs each day instead).
• This process of loss and regrowth is continuous and natural - it is only when daily hair loss greatly exceeds this rate that an unnatural condition may be present.

• A sebaceous gland is attached to each follicle. It produces sebum (oil), which lubricates the hair and allows it smooth passage as it grows along the follicle. In excess, sebum can cause spots due to bacterial infection.
• Generally speaking, follicles that form an angle to the skin will give rise to straight hair, and follicles that curve downwards into the dermis of the skin will give rise to curly hair.
• Arrector pili muscles are attached to the follicles. When they contract, hair stands on end (giving us goose bumps). This traps air to help keep the body warm. (Nerve ending deviations of these muscles may explain the very rare changes from straight to wavy hair or vice versa).