ABSTRACT
In order to the understand hair loss, it is vitally important to understand what is normal hair growth. An average person has 100,000 to 150,000 terminal hair follicles on his or her scalp ( 1 ). Hair follicles produce approximately 1 cm of new hair growth in a month ( 2 ). All human hair grows in cycles. For scalp hair, the growing phase (anagen) accounts for 85-90% of the hair and lasts for approximately two to six years. The shedding phase (catagen) accounts for about 1% of the scalp and lasts for approximately three weeks. Finally, the resting phase (telogen) accounts for approximately 10% of the scalp and lasts approximately three months ( 3 ). It is typical for an average person to shed between 50 and 100 strands of hair per day ( 4 ). Shedding of the hair is normal since new strands of hair will begin growing in those follicles. This cycle continues to repeat itself throughout a person’s life.
