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Hair loss is a common problem in men and women. Correct diagnosis of hair disorders is complex and requires evaluation of clinical presentation, history, physical examination, and laboratory tests. Hair loss may be categorized as hair shaft abnormalities, permanent alopecia, or nonpermanent alopecia. Nonpermanent alopecia, the most common type, includes androgenetic alopecia, telogen effluvium, alopecia areata, and traction alopecia. The hallmark of this group is the possibility of complete regrowth with adequate treatment.
Hair loss, or alopecia, is one of the most distressing disorders for both adults and children because our society places a great emphasis on physical appearance. Women, children, and adolescents with hair loss may be especially troubled by their appearance. The importance of the patients cosmetic concerns should not be underestimated.
The etiology of alopecia may be somewhat confusing, as it is associated with a wide variety of causes. Some cases are best managed with reassurance and education, whereas others require medical evaluation and therapy.
In this article, the hair cycle and the common causes of hair loss are reviewed. The most common types of hair loss - androgenetic alopecia, telogen effluvium alopecia areata, and traction alopecia - along with current treatment modalities are reviewed.
The Life Cycle of Hair
In healthy individuals, hair grows at a rate of approximately 0.35 mm/day. Each follicle passes through a life cycle with phases of growth or anagen, involution or catagen, and rest or telogen (Sperling & Mezebish, 1998). At the end of the telogen phase, hair is shed and a new cycle is initiated. For hairs on the scalp, the anagen phase lasts 2 to 5 years; more than 85% of hair follicles are in this phase at any time. Catagen is a transitional phase lasting 3 to 6 weeks. Telogen lasts about 3 months, and up to 15% of hair follicles are in this phase at any time (Bergfeld, 1989). Hair growth is asynchronous, with growing, resting, and shedding hair shafts distributed randomly. Each day, up to 100 hair follicles finish the telogen phase and are shed from the scalp, and about the same number enter the anagen phase (Epstein & Cotsarelis, 1999).
In a normal scalp, the total number of follicles and the density of follicles are constant. Therefore, it...