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

It is most common in people younger than 20. But it can happen to children and adults of any age.

• Usually clumps of hair 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).
• In rare cases, complete loss of scalp hair and body hair occurs.
• Hair may grow back completely, partially, or not at all. In most people with the condition, the hair grows back within a year.

Medical treatments for alopecia areata may include medicines that are either put on the skin or injected. But because hair often grows back, treatment may not be needed.