There are two types: 

  1. Scarring alopecia, where there is fibrosis, inflammation, and loss of hair follicles.
  2. Nonscarring alopecia, where the hair shafts are gone but the hair follicles are preserved, making this type of alopecia reversible.

Alopecia areata, also known as spot baldness, is an autoimmune disease in which hair is lost from some or all areas of the body, usually from the scalp, due to the body’s failure to recognize its own body cells and subsequent destruction of its own tissue. Often it results in bald spots on the scalp, especially in the first stages. In 1–2% of cases, the condition can spread to the entire scalp (alopecia totalis) or to the entire skin (alopecia universalis).