Medications such as steroids and birth control pills, or the surgical removal of sex glands may stimulate abnormal hair growth. Hair forms in a pouchlike structure below the skin called a hair follicle. What we see as hair is actually the hair shaft, which is the keratinized, hardened tissue that grows from this follicle. People have more hair follicles per square inch than chimpanzees and gorillas. Because most of the hair is fine and pale it usually isn't visible to the naked eye.
Hair grows through three distinct growth phases.
Active growth phase called the Anagen stage which can last several years. Regressive phase called the catagen stage which lasts about two weeks, during which the hair stops growing but is not yet shed. Resting phase called Telogen stage which lasts about 5-6 weeks, at the end of which the hair falls out and a new hair begins to form. The method you choose for dealing with unwanted hair will depend on the number and location of hairs and how great a problem you perceive them to be. Temporary methods such as shaving, depilatories and bleaching are popular but not very satisfying.