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Hair loss, either temporary or permanent, may occur for a variety of reasons. Hair loss may be reversed through medication or surgical procedures. The loss of one's hair can cause concern as attractiveness and youth are often linked to the presence of hair. Hair loss usually develops gradually and may be patchy or diffuse.
Common symptoms of hair loss include:
* Thinning hair on the scalp, a receding hairline, or a horseshoe-shaped pattern that leaves the crown of the head exposed (androgenic alopecia in men)
* Thinning of hair at the crown (androgenic alopecia in women)
* Sudden loss of patches of hair, usually in a smooth circular pattern (alopecia areata).
* Complete loss of all hair on the body (a rare disease called alopecia universalis)
* Patches of broken hairs and incomplete hair loss, usually on the scalp but sometimes involving the eyebrows. This condition (trichotillomania) often occurs in children and is associated with a history of rubbing or pulling at hair.
* Loss of "clumps" of hair after various illnesses and drug treatments, rapid weight loss, anemia, stress, or pregnancy (telogen effluvium)
Causes
Roughly 100 hairs are lost from the average head every day. The average scalp contains about 100,000 hairs. Each individual hair survives for an average of four and a half years, during which time it grows about half an inch a month. Usually in its fifth year, the hair falls out and is replaced within six months by a new one. There are three stages of hair growth:
* The anagen phase lasts for about three years. Most hair is in this stage at any point in time.
* The transitional or catagen phase contains a small percentage of hair at a time (2%-3%).
* The final, or telogen phase contains about 10% of hair. This is a resting phase which lasts about three months. When the hair dies, it is ejected and a small nodule is left at the hair shaft.
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