Alopecia areata is
a condition that causes unpredictable hair loss in patches.

It is an
autoimmune disorder, 

where your immune system attacks your hair follicles by mistake.

Alopecia areata commonly affects the head scalp,

but it can impact hair growth anywhere on the body.

Roughly 147 million people have or will develop alopecia areata globally. 

treatments can only help milder cases. 

The hair growth may also start
by itself.

scientists have not been able to find a cure for alopecia areata yet.