Immune Privilege Collapse and Alopecia Development: Is Stress a Factor?

Abstract

Stress as a cause of hair loss has been the subject of anecdotally shared knowledge for decades; however, the molecular link underlying this process has yet to be fully elucidated. To protect against hair loss and to enable regeneration, the hair follicle is thought to enjoy immune privilege similar to select other regions of the body. A growing body of evidence suggests that collapse of this hair follicle immune privilege (HFIP) contributes to the pathogenesis of autoimmune hair loss disorders, including alopecia areata (AA) and lichen planopilaris (LPP). One possible trigger for the process of HFIP collapse in autoimmune hair loss is stress. This review appraises the current literature to shed light on molecular mechanisms for HFIP collapse that lead to hair loss, as well as role that neurogenic stress plays in triggering this process. While research in this field is still nascent, current evidence suggests that skin has its own system analogous to an “endocrine axis” that may be vulnerable to stress, which is one possible explanation bridging the link between stress and hair loss.