Revisiting Atopy: The IgE-Dependent Amplification Loop as a Forgotten Driver of Atopic Dermatitis.

Atopic dermatitis (AD) is increasingly interpreted through frameworks emphasizing barrier dysfunction, type 2 cytokine signaling, pruritus pathways, and microbial dysbiosis, often relegating IgE-mediated mechanisms to secondary roles. In this narrative review, we synthesize historical, clinical, immunologic, and histopathologic evidence to propose a conceptual model in which IgE-bearing antigen-presenting cells (APCs)-including Langerhans cells, inflammatory dermal dendritic cells, and inflammatory dendritic epidermal cells (IDECs)-participate in an IgE-dependent amplification loop that may contribute to the chronicity of extrinsic (IgE-associated) AD. Evidence from human studies indicates that FcεRI-expressing APCs can acquire environmental allergens through IgE, enhancing antigen uptake and T-cell activation, while mast cells and basophils further reinforce type 2 inflammation through IgE-dependent and IgE-augmented pathways. Although these mechanisms have been described across distinct experimental and clinical contexts, their integration into a unified pathogenic circuit remains hypothesis-driven. We therefore present an interpretive framework that organizes these partially validated mechanisms into a coherent model linking cutaneous sensitization, allergen capture, APC activation, Th2 polarization, and spongiosis formation. This conceptual synthesis aims to reposition IgE-mediated processes within the broader pathophysiology of extrinsic AD and to highlight potential therapeutic implications for targeting IgE-FcεRI signaling and IgE-dependent APC biology.