Alopecia areata is a type of hair loss that affects the hair on the scalp or other areas of the body. The condition happens when the immune system mistakenly attacks hair follicle roots, where hair growth begins.

This type of hair loss is most common in young people, but it can happen at any age.

Clumps of hair may fall out, resulting in totally smooth, round hairless patches. In some cases, the hair may become thinner without distinct patches of baldness. This type of hair loss may happen more than one time (recur).

Hair may grow back completely, partially, or not at all. For many people, the hair grows back within a year.

Because the hair often grows back within a year, treatment may not be needed. Treatment may include medicines that are either put on the skin or injected.