Causes
Alopecia areata is not contagious. It occurs more frequently in people who have affected family members, suggesting that heredity may be a factor. Strong evidence that genes may increase risk for alopecia areata was found by studying families with two or more affected members. This study identified at least four regions in the genome that are likely to contain alopecia areata genes. In addition, it is slightly more likely to occur in people who have relatives with autoimmune diseases.
The condition is thought to be an autoimmune disorder in which the body attacks its own hair follicles and suppresses or stops hair growth. For example, T cell lymphocytes cluster around affected follicles, causing inflammation and subsequent hair loss. There are a few recorded cases of babies being born with congenital alopecia areata; however, these are not cases of autoimmune disease because an infant is born without a fully developed immune system.
There is some evidence that alopecia affects the part of the hair follicle that is associated with hair color. Hair that has turned gray may not be affected.
Read more about this topic: Alopecia Areata