It has an autoimmune origin, that is, the body own defenses attack the hair root, causing inflammation that causes it to fall out and not grow again until the inflammation stops. The reason why this inflammatory reaction is triggered is completely unknown. There is evidence that genetics influences the development of alopecia areata. Stress can act as a trigger.

The evolution of alopecia areata is unpredictable, it can last a few months or many years. As it is an autoimmune process, alopecia can present episodes of improvement even without treatment, but in the same way it can be "active" and lose hair for a long time. In these cases, the treatment will be able to make the hair reappear, but as the treatment is withdrawn, there is a possibility that it will be lost again.