How Does Hair Grow?
Hair grows according to location on the body, genetic background, age, and sexual hormonal influences. There are three phases of each cycle: growing, resting and falling. These phases are also known as anagen, telogen, and catagen, respectively.
At least 85% of the hairs on the scalp are growing at one time. Normal daily hair shedding of 50-100 hairs per day can be expected. Scalp hairs grow about one half inch per month. The growth cycle of each individual hair can be up to several years before shedding. The growth cycle of eyebrow hair is very short and the resting period very long compared to that of scalp hair.