Alopecia Areata and Atopic Dermatitis: Common Mechanisms and Emerging Therapeutics.

Alopecia areata (AA) and atopic dermatitis (AD) have historically been classified as immunologically distinct-AA as a T helper 1 (Th1) driven autoimmune condition and AD as a T helper 2 (Th2) polarized inflammatory disease. However, emerging evidence demonstrates substantial immunological overlap, with both conditions exhibiting multi-axis cytokine dysregulation converging on Janus kinase-signal transducer and activator of transcription (JAK-STAT) dependent signaling and regulatory T cell insufficiency/dysfunction. Epidemiologically, these conditions frequently co-occur: up to 40% of AA patients have atopic comorbidities. Both diseases share genetic susceptibility loci, including interleukin 13 (IL-13) and human leukocyte antigen (HLA) associations, further supporting convergent pathogenic mechanisms. Key shared biomarkers include elevated interleukin 4 (IL-4), IL-13, and IgE, alongside dysregulated interferon-gamma and interleukin 15 signaling through the JAK-STAT pathway. These mechanistic insights have catalyzed the development of therapeutics for both conditions. JAK inhibitors-including baricitinib, ritlecitinib, upadacitinib, and abrocitinib-have demonstrated efficacy in AA and/or AD by interrupting cytokine signaling central to both diseases. Dupilumab, an interleukin -4 receptor alpha antagonist FDA-approved for AD, has demonstrated benefit in a specific subset of AA patients with concurrent atopic disease; these findings highlight pathophysiologic heterogeneity within the disease and support the need for endotype-stratified treatment strategies. Investigational therapies targeting the OX40/OX40 ligand costimulatory pathway, interleukin 2 receptor agonists (rezpegaldesleukin), interleukin 7 receptor antagonists (bempikibart), and tri-specific cytokine inhibitors (EQ101) represent the next generation of agents that may treat both conditions by restoring immune homeostasis rather than broadly suppressing immunity. In this narrative review, we synthesize current understanding of the shared immunopathogenesis of AA and AD and highlight approved and investigational therapeutics with dual-disease relevance, pointing toward an era of mechanistically targeted, potentially disease-modifying interventions.