Alopecia areata (AA) usually manifests as patches of non-scarring hair loss due to immune dysregulation.However, more severe forms may affect the entire scalp (alopecia totalis: AT) or body hair including eyebrows, cilia, axillary hair and hair of the pubis (alopecia universalis: AU). 

Alopecia areata (AA) is an autoimmune inflammatory disease of the hair follicles, and to a lesser extent the nails, leading to non-scarring patches of hair loss, mainly on the scalp, though any hair-bearing skin can be affected. As a part of the disease process, T lymphocytes surround the anagen hair follicle bulb, a site that is normally immune privileged, causing the arrest of hair shaft growth, while the hair follicle itself is preserved.1–3 Genetic predisposition was revealed by a genome-wide association study that linked 139 single nucleotide polymorphism to AA.4 Environmental factors, including stress, infections, vaccinations, and diet, have less proven impact on the induction or exacerbation of the disease.

Various treatment options are available that should be tailored to disease severity and extent, as well as the psychological impact on the patient. Intralesional steroids, usually triamcinolone acetonide (TA) in 2.5–10 mg/mL doses, are traditionally among the first treatment options for AA in adults. 

References:

[1]https://systems.enpress-publisher.com/index.php/ti/article/view/149

[2]https://link.springer.com/chapter/10.1007/978-3-211-99225-8_20

[3]https://www.nature.com/articles/nm.3645

[4]Perera E, Yip L, Sinclair R. Alopecia areata. In: Alopecias-Practical Evaluation and Management. Vol. 47. Karger Publishers; 2015:67–75.