Core Viewpoint - The article discusses the relationship between stress and hair loss, highlighting recent research that reveals the mechanisms by which acute stress can lead to hair follicle damage and subsequent autoimmune responses [3][18]. Group 1: Mechanisms of Stress-Induced Hair Loss - Chronic stress leads to the suppression of hair follicle stem cell activation, resulting in hair loss due to prolonged resting phases of hair follicles [2]. - Acute stress causes immediate hair loss by activating the sympathetic nervous system, which leads to necrosis of rapidly dividing hair follicle transit-amplifying cells (HF-TAC) [3][19]. - The necrosis of HF-TAC releases cellular debris that triggers macrophage-mediated clearance and activates dendritic cells, which can lead to the activation of autoreactive T cells that attack hair follicles in the future [3][15]. Group 2: Observations from Research - The research utilized mouse models to study the effects of acute stress on hair follicles, revealing that stress significantly impacts HF-TAC while sparing hair follicle stem cells (HFSC) [7][9]. - The study found that stress-induced hair loss is closely linked to the sympathetic nervous system rather than solely relying on stress hormones like adrenaline [10][19]. - The inflammatory response following necrosis differs from normal hair follicle regression, as it involves necrosis rather than apoptosis, leading to a more pronounced inflammatory reaction [12][13]. Group 3: Long-Term Implications of Stress - The findings suggest that stress not only causes immediate hair loss but may also initiate autoimmune processes, with necrotic hair follicle cells releasing self-antigens that activate autoreactive CD8+ T cells [15][18]. - Even after hair follicles recover from initial stress, these activated T cells can persist and attack hair follicles upon subsequent inflammatory stimuli, explaining the sensitivity to future hair loss [15][20]. - The research emphasizes the importance of managing stress levels for individuals with alopecia or a family history of autoimmune diseases, as it may help prevent disease recurrence [20][21].