Alopecia areata is a type of hair loss that occurs when your immune system mistakenly attacks hair follicles camera.gif, which is where hair growth begins.The damage to the follicle is usually not permanent. Experts do not know why the immune system attacks the follicles.Alopecia areata is most common in people younger than 20, but children and adults of any age may be affected. Women and men are affected equally.
