The Central Role of Th2 Immune Response in Inflammatory Dermatoses: From Pathogenesis to Targeted Therapies

Th2 cells that produce interleukin (IL)-4, IL-5, IL-13, and IL-31, promoting immunoglobulin E (IgE) class switching, eosinophil recruitment, mast cell degranulation, and pruritus. We aimed to place these conditions in context and clarify how Th2 biology informs diagnosis and therapy. We conducted a narrative synthesis of mechanistic, translational, and clinical evidence on Th2 pathways in atopic dermatitis (AD), prurigo nodularis, bullous pemphigoid, chronic spontaneous urticaria, and selected type I/IVb hypersensitivity reactions, with focused appraisal of trials targeting IL-4Rα, IL-13, and IL-31R. Persistent Th2 activation is associated with epidermal barrier dysfunction, immune dysregulation, and pruritogenic neural signaling; AD is the archetype, showing prominent lesional IL-4/IL-13 activity correlated with severity and itch. Across disorders, pathway-directed biologics against IL-4Rα, IL-13, and IL-31R consistently reduce disease activity and pruritus in AD and prurigo nodularis, with emerging signals of benefit in bullous pemphigoid and chronic spontaneous urticaria. The Th2 axis provides a unifying pathogenic framework and actionable therapeutic target across multiple dermatoses. Integrating cytokine profiling with clinical phenotypes may refine patient stratification and optimize the deployment of existing and next-generation Th2-targeting therapies.