Most scalp hair grows steadily. After a growth phase that
lasts between 2 and 6 years, scalp hair enters a resting phase that lasts 2 to
3 months. Hair is shed at the end of the resting phase.
normally sheds from 50 to 100 hairs a day. After a hair is shed, it is replaced
by a new hair from the same follicle, and the growing cycle starts again. Scalp
hair grows about
0.5 in. (1.3 cm) per month. As
people age, their rate of hair growth slows.