The disease, which strikes about 1 percent of the population by age 50 in a rather random fashion, creates isolated patches of hair loss that can come and go or linger and, either way, make life very difficult, researchers say. Alopecia areata is believed to be an autoimmune disease, not unlike lupus or arthritis, but this time the ill-fated target of the immune system appears to be an antigen on the hair follicle.
Antigens are proteins normally present in the body and ignored by the immune system.
Normally the hair follicle is in a state of flux which Dr. Sangueza compares to a yo-yo. The follicle will retract, go into a resting phase and become very small, then become larger and extend deeper into the scalp. We lose hair during the resting state. Alopecia areata sends the hair follicle into an abnormal state of rest that results in one or more large patches of missing hair, Dr. Casanova said. The hair root is still present.