Information on alopecia areata

Under normal circumstances, hair growth in each hair follicle occurs in a cycle. There are three main phases of the hair growth cycle; anagen, catagen, and telogen. Anagen is the active growth phase when hair fiber is produced. This is followed by catagen, a period of controlled regression of the hair follicle. Ultimately the hair follicle enters telogen where it is in a so-called resting state. Alopecia areata primarily affects the hair follicle as it enters the anagen phase. Inflammatory cells of the immune system infiltrate around anagen hair follicles and cause them to stop producing hair fiber.

Studies indicate that the initial event in the development of alopecia areata is the premature precipitation of anagen follicles into the telogen, resting state of the hair follicle cycle. Most commonly, hair follicles exit anagen, enter catagen, and then shed the hair fiber upon entering telogen. The follicles may then proceed back into the next anagen growth phase but, because of the continued activity of the disease, produce poor aberrant hair fiber. Such follicles are described as being in a dystrophic anagen state. Some researchers believe the hair follicles continue indefinitely to oscillate between several rapid cycles of dystrophic anagen and telogen states. Others believe many of the follicles are eventually arrested in telogen.

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