Alopecia

Definition

Alopecia is the absence or thinning of hair in an area of the body where hair formerly grew. It may be caused by physical damage to the hair itself or to the hair follicles, but is most often the result of changes in the natural hair growth cycle.

The average scalp has about 100,000 hairs. Most of these hairs are in the anagen, or growing, phase, which may last as long as five years. In the catagen, or transitional, phase, the hair stops growing and the follicle begins to shrink. The hair then falls out and the follicle lies dormant in the telogen, or resting, phase until a new anagen phase begins. About 10% of the hair follicles on the normal scalp are in the transitional or resting phases, and about 100 hairs are lost every day. In some types of alopecia, the growth cycle is disrupted by some temporary situation such as a chemical imbalance or stress; often the problem may be resolved when the precipitating condition is alleviated. However, 95% of cases of hair loss in both men (male pattern baldness) and women (female diffuse baldness) are genetic in origin. This is called androgenetic alopecia. Read the rest of this entry »

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