what alopecia

Alopecia is a medical term for hair loss or baldness. Alopecia areata is a type of hair loss that occurs when the immune system attacks hair follicles, causing patchy hair loss anywhere on the body, but it most commonly affects the hair on the scalp. The onset of alopecia areata can be at any age, but most people get it in their teens, twenties, or thirties. The disease often causes patchy hair loss, which is why it is usually called alopecia areata. There are different classifications of alopecia areata depending on the amount of hair lost and where it is lost on the body. Alopecia barbae is when a person has patchy hair loss on their beard, alopecia ophiasis is when a person has a band or strip of hair loss on their scalp, alopecia totalis is when a person has lost all the hair on their scalp, and alopecia universalis is when a person has lost all the hair on their scalp and everywhere else on their body. The disease is caused by an autoimmune response, where the immune system attacks hair follicles because it thinks they are foreign invaders. There is no cure for alopecia areata, but medications and therapies can help hair regrow.