Hair Loss Overview
The loss of hair (alopecia) is a natural phenomenon in all hair-baring animals that normally occurs during the hair growth cycle. It is estimated that most individuals (assuming they have a full head of hair) lose about 100 scalp hairs over a 24-hour period. Hair loss can become a cosmetic problem when it occurs in the wrong place at the wrong time in the wrong individual. True hair loss should be distinguished from damage to the hair shaft, which may cause breakage close to the scalp. This sort of damage is often caused by exogenous chemicals used to alter the physical characteristics of the hair shaft (hair dye, etc.) or other forms of self-manipulation, but certain genetic diseases can alter its strength and durability.
Physicians divide cosmetically significant hair loss into two categories.
There are three cycles of hair growth: growing (80% of follicles), resting, and shedding. In human hair, each follicle cycles at its own individual rate as opposed to most animals, where these cycles change with the season, and all hairs are in the same part of the cycle at the same time. This is why animals grow a thicker coat in the fall and shed most in the spring and why human beings do not shed. Unlike most animals, in humans, each hair has its own pattern of growing, resting, and shedding.
Medically Reviewed by a Doctor on 6/20/2014