Alopecia areata (AA) is an immunologically mediated disease characterized by non-scarring hair loss (Madni and Shapiro, 2000). AA is presented by rapid and complete hair loss in one or more round or oval patches, usually on the scalp, beard area, eyebrows, eyelashes, and less commonly, on other hairy areas of the body (Berker et al., 2010 and James et al., 2011) Alopecia areata is a T-cell-mediated autoimmune disease. There is a complicated interplay between loss of immune privilege in the hair follicle, autoimmune-mediated hair follicle damage, and activation of inflammatory pathways that have been argued to explain the development of this disorder, but the exact pathophysiology of AA remains unknown. Hair follicles are infiltrated by autoreactive CD8 and CD4 T lymphocytes, which attack hair follicle-derived autoantigens while sparing the stem compartment (Rajabi et al., 2018).
Alopecia areata can be treated with topical and/or intralesional corticosteroids, which are the treatment of choice. Anthralin, minoxidil, coal tar, and topical immunotherapy are examples of other topical treatments. Systemic immunosuppressants such as cyclosporine, systemic steroids, Janus kinase inhibitors, and methotrexate may be considered in severe resistant cases (lee and lee, 2017).
Intralesional triamcinolone acetonide is preferred in cases of AA , as it is well known as anti-inflammatory and interferes with local immunity of the skin, which helps in the recovery of the disease, but if used in wrong technique or given in a high dose, it might cause all the side effects of corticosteroid, especially skin atrophy (Berker et al., 2010).
Lactic acid is a member of alpha-hydroxy acids. It has been used in the treatment of many skin diseases, like AA and vitiligo. Lactic acid stimulates spontaneous secretion of vascular endothelial growth factor (VEGF) by human reconstructed epidermis. VEGF is an angiogenic cytokine involved in angiogenesis and wound healing and stimulates the growth of hair follicles resulting in recovery of AA. Other studies suggest that lactic acid may act through its irritant effect (Al-Tammimy, 2005).
Vitamin D interacts with the innate and adaptive immune systems in a variety of ways, the majority of which contribute to its downregulation (Nancy and Yehuda, 2009). It has a powerful effect on T and B lymphocytes, influencing their activation responses (Arnson et al., 2007).
All cells of the immune system express 1,25-dihydroxyvitamin D3 receptors (VDRs) and are therefore vulnerable to calcitriol-mediated modulation. Vitamin D3 has the ability to influence the migration and maturation of different dendritic cell subtypes and their production of chemokines and cytokines, giving them an immunoregulatory and tolerogenic role (Illescas-Montes et al., 2019) It has been shown that VDRs are highly expressed in the keratinocytes of human hair follicles and the absence of their expression is associated with reduced hair follicle growth and epidermal differentiation. Reduced VDR expression in the hair follicles of affected areas has also been observed in studies of AA patients' scalp (Çerman et al., 2015).
Microneedling (MN) is a technique that comprises puncturing the skin repeatedly with sterile microneedles (Iriarte et al., 2017). It promotes hair regeneration by triggering stem cells in the hair bulge, which results in the generation of growth factors. It also improves blood circulation to the hair follicles and influences the local immune cells (Chandrashekar et al., 2014). Moreover, combining MN with applied topical drugs facilitates their absorption through the microchannels created within the epidermis (Fertig et al., 2018).