The causes for Alopecia areata are still incompletely known, but most speak for an organ-specific autoimmune process that results in follicle destruction. Often, triggering causes are found - most common are emotional stress but also some diseases such as infections can occur. No reliable incidence data exist but area can occur at any age, most commonly in the 20-50 age group. There seems to be no difference between gender. Initially it occurs as one or more bold spots 2-3 cm in size, which can then grow large in a few weeks up to a few months. In some cases the size of the spot does not change and in other cases it disappears again and then re-emerges. Most, (an estimated 90%), will not lose all their hair but instead have periods when they get new bald spots.