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| Definition: | Alopecia is the partial or complete loss of hair.
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| Alternative Names: | Loss of hair; Alopecia; Baldness
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| Considerations: | Baldness is determined by multiple genetic factors. It is not always true that baldness follows the mother's line or anyone else's, or that it skips generations.
Both men and women lose hair density as they age. Men develop a typical pattern of baldness, associated with the presence of the male hormone testosterone. Men who do not produce testosterone (because of genetic abnormalities or castration) do not develop this pattern of baldness. Many women also develop a characteristic pattern of hair loss. See male-pattern baldness; female-pattern baldness.
Occurring most often on the scalp, alopecia usually develops gradually and may be all over (diffuse) or patchy.
Usually baldness is not caused by a disease, but is genetic. Inherited or "pattern baldness" affects many more men than women. About 25% of men begin to bald by the time they are 30 years old, and about two-thirds are either bald or have a balding pattern by age 60.
On average, about 100 hairs are lost from the head every day. The average scalp contains about 100,000 hairs (blondes 140,000, brunettes 155,000 and redheads only 85,000).
Each individual hair survives for an average of 4.5 years, during which time it grows about half an inch a month. Usually in its 5th year, the hair falls out and is replaced within 6 months by a new one. Genetic baldness is caused by the body's failure to produce new hairs and not by excessive hair loss.
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Review Date: 4/15/2003
Reviewed By: Michael Lehrer, M.D., Department of Dermatology, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.
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The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 2003 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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