Alopecia areata (patchy baldness) is a relatively common autoimmune disease that causes hair loss on the scalp or other parts of the body in both men and women. The cause of the disease is unknown. Unlike androgenetic alopecia (male pattern baldness), hair regrowth is always possible in people with alopecia areata.

In most instances, alopecia areata does not progress beyond a few bald patches. However, it can cause complete baldness of the head (alopecia areata totalis) or complete hair loss on the head, face and body (alopecia areata universalis) in very rare cases. Some individuals may also develop "pits" or dents in the fingernails as a result of the disease.

Cases of alopecia areata vary depending on the individual. Some experience only minimal hair loss, followed by regrowth with the condition never recurring. Others lose and regrow their hair indefinitely. Some research suggests a combination of certain genes may make some people more likely to develop the disease. People with family members affected by alopecia areata have a slightly higher risk for the disease, particularly if the first patches of hair are lost before age 30.

Alopecia areata can be diagnosed by a physician. However, medical attention is not necessary for individuals with alopecia areata because the disease poses no health risks.

There is no cure for alopecia areata, nor are there any specifically approved treatments. Although they do not prevent new bald patches from happening, some medications approved for other purposes may be useful in regrowing hair (e.g., corticosteroids).