Alopecia areata is referred to as a condition when there is a loss of hair from certain or all the areas of human body; however, it is more concentrated in the scalp area. This generally results in the formation of bald spots on the scalp. Sometimes it is also termed as spot baldness, particularly in the early stages. In extremely rare cases (1%-2%) this condition might affect the entire scalp, termed as Alopecia totalis or the whole of epidermis also know as Alopecia universalis.  These conditions occur in other species too, the causes being similar.

This condition is apparent in 0.1%-0.2% of humans; both males and females are affected, but are believed to be more prevalent in females than in males. Initially, this condition is widespread in late teens, early in the childhood or young adulthood. It happens with the people of all ages and the common types are as follows:

• Diffuse Alopecia areata – A condition which causes diffused hair loss over scalp.
• Alopecia areata monolocularis – Concentration of baldness at a particular spot, anywhere on the head.
• Alopecia areata multilocularis -  Hair loss in multiple regions
• Alopecia areata barbae – If the disease is limited to the beard
• Alopecia areata totalis – Complete loss of hair on the scalp
• Alopecia areata universalis – Entire body hair including the public hair is lost