Alopecia areata is a condition that causes hair loss in small patches. The patches can be almost unnoticeable, but can sometimes connect and then become more noticeable. The condition develops when the immune system attacks the hair follicles, resulting in hair loss.

Sudden hair loss may occur on the scalp, and in some cases the eyebrows, eyelashes, and face, as well as other parts of the body. It can also develop slowly and recur after years between instances. Doctors don’t know why it happens. But they think people who get it have something in their genes that makes it more likely. Then something happens to trigger the hair loss.

The condition can result in complete hair loss, called alopecia universalis, and it can prevent hair from growing back. When hair does grow back, it’s possible for the hair to fall out again. The extent of hair loss and regrowth varies from person to person. There’s currently no cure for alopecia areata.