What causes alopecia areata?
Alopecia areata is an autoimmune disease that causes your immune system to attack your body. Your immune system attacks your hair follicles because it thinks they’re foreign invaders — bacteria, viruses, parasites or fungi — that cause infection, illness and disease. When this happens, your hair begins to fall out, often in clumps the size and shape of a quarter. The extent of the hair loss varies. In some cases, it’s only in a few spots. In others, the hair loss may be more significant, including total hair loss. Your genetic makeup (the parts of your cells that determine your physical traits, like eye color, height or hair color) may trigger your body’s autoimmune reaction. Or your genetic makeup combined with a virus or another substance you encounter may trigger the reaction.