Alopecia areata is sudden loss of patches of hair when there is no obvious cause such as a skin or general bodywide disorder.
Alopecia areata is common. It occurs in both sexes and at all ages but is most common among children and young adults.
The cause is believed to be an autoimmune reaction in which the body’s immune defenses mistakenly attack the hair follicles. Alopecia areata is not the result of another disorder, but some people may also have an associated thyroid disorder or vitiligo (a skin pigment disorder).
Round, irregular patches of hair are suddenly lost. Around the edges of the patches are characteristic short, broken hairs, which resemble exclamation points. The site of hair loss is usually the scalp or beard. Sometimes all the scalp hair is lost (alopecia totalis), or hair is lost from around the side and back edges of the scalp (ophiasis). Rarely, all body hair is lost (a condition called alopecia universalis). The nails may become pitted or rough. The hair usually grows back in several months. In people with widespread hair loss, regrowth is less likely.
Doctors examine the scalp, body surface, and nails. To rule out other disorders, doctors may do testing.
Alopecia areata can be treated with corticosteroids. For small bald patches, corticosteroids are typically injected under the skin of the bald patch, and minoxidil may be applied directly to the bald patch as well. For larger patches, corticosteroids can be applied to the scalp or, more rarely, taken by mouth. Another treatment for alopecia areata involves applying irritating chemicals, such as anthralin or diphenylcyclopropenone, to the scalp to induce a mild allergic reaction or irritation. The irritation sometimes promotes hair growth.
The doctor and person may choose to allow alopecia areata to resolve on its own, which sometimes happens without treatment.