Narrative Review of the Role of Reactive Oxygen Species in Allergic Rhinitis.

Studies of allergic rhinitis (AR) have increasingly recognized that reactive oxygen species (ROS) are not simply byproducts of oxidative metabolism but function as modulators of the type 2 inflammatory network during the pathogenesis of this disease. This narrative review summarizes the role of ROS in the pathophysiology of AR by analyzing studies that examined markers of systemic oxidative stress, dysfunction of the epithelial barrier, ROS derived from immune cells, mitochondrial redox signaling, and inflammasome-related pathways. Our structured search of the literature reviewed five major databases (PubMed, Scopus, EMBASE, Cochrane Library, and Google Scholar) and identified 17 eligible studies published between 2000 and 2026. Clinical studies suggest that patients with AR exhibit altered systemic redox homeostasis, including thiol-disulfide imbalance and increased lipid peroxidation. However, these findings are primarily from measurements of markers in peripheral blood, not nasal mucosa. Experimental studies consistently demonstrated that allergen exposure increased the levels of ROS in nasal epithelial and immune cells, disrupted the epithelial barrier, downregulated tight junction proteins, and activated inflammatory signaling pathways. Although direct nasal tissue data remain limited, evidence extrapolated from peripheral blood and bronchial challenge models suggests that eosinophils and neutrophils contribute to the generation of ROS during the late phase of the allergic response, thereby potentially amplifying and sustaining airway inflammation. There is also evidence that mitochondrial ROS and DUOX-dependent signaling contribute to epithelial dysfunction, including the release of damage-associated molecular patterns and activation of inflammasome pathways. In parallel, antioxidant defense mechanisms, such as the KEAP1/NRF2 axis and mitophagy-related pathways, appear to modulate disease severity by maintaining redox homeostasis. Experimental strategies such as ROS scavengers and oxidative stress-responsive drug delivery systems have shown early proof-of-concept potential in preclinical and pilot studies, but rigorous and large-scale clinical support is strictly required before any clinical application can be considered. Overall, current evidence indicates that ROS function in AR as context-dependent redox mediators rather than as primary causes. The biological effects of ROS appear to depend on site of synthesis, subcellular localization, and the balance between oxidant generation and antioxidant defenses. Further studies that directly assess the dynamics of nasal mucosal ROS and well-designed clinical trials are needed to clarify the translational relevance of these studies and the therapeutic potential of different treatments for AR.