Alopecia areata is common. It occurs in both sexes and at all ages but is most common among children and young adults.
The cause of alopecia areata 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 a coexisting 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), hair is lost from around the side and back edges of the scalp (ophiasis), or hair is lost on the top of the head but not at the edges of the scalp (sisaipho). Rarely, all body hair is lost (a condition called alopecia universalis).
The nails may become pitted or rough, or the half moon at the base of the nails (the lunula) may be red.
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.
Other treatments for alopecia areata involve applying chemicals, such as anthralin, diphenylcyclopropenone, or squaric acid dibutylester to the scalp to induce a mild irritant reaction or mild allergic reaction, which sometimes promotes hair growth. These treatments are usually given to people who have widespread hair loss and who have not been helped by other treatments.
For more severe cases, people may be given methotrexate taken by mouth. This drug may be combined with corticosteroids taken by mouth. Drugs called Janus kinase (JAK) inhibitors, which are used in treating other autoimmune and blood disorders, may be useful in treating alopecia areata.
The doctor and person may choose to allow alopecia areata to resolve on its own, which sometimes happens without treatment in more mild cases. In some people, the hair may grow back in several months. In people with widespread hair loss, regrowth is less likely.