Smell loss is often dismissed as a minor nuisance, yet for the estimated 10-15% of adults living with chronic rhinosinusitis, olfactory dysfunction can erode food enjoyment, safety awareness, and emotional well-being in ways that standard quality-of-life tools rarely capture. A growing body of mechanistic evidence now reframes this symptom from a simple drainage problem into a complex neuroimmune injury — with implications for how aggressively clinicians should intervene.
The review synthesizes current understanding of how chronic rhinosinusitis — particularly the nasal-polyp subtype — damages olfaction through three overlapping pathways. The classical explanation of physical obstruction at the olfactory cleft turns out to be only part of the story. A type-2 cytokine milieu, dominated by IL-4, IL-5, and IL-13 alongside eosinophil infiltration and elevated IgE, directly injures the olfactory epithelium and suppresses neurogenesis, the process by which olfactory receptor neurons regenerate. More provocatively, the authors highlight evidence that peripheral sinonasal inflammation may trigger central neural remodeling in olfactory-processing regions of the brain — a mechanism that could explain why some patients fail to recover smell even after anatomical obstruction is resolved. Objective psychophysical testing, rather than patient self-report, is emphasized as essential for accurate baseline assessment and outcome tracking.
This conceptual shift carries real clinical weight. If sensorineural and central mechanisms are responsible for a meaningful share of persistent smell loss, then surgical decompression alone — even successful functional endoscopic sinus surgery — may be insufficient for full recovery. Biologic agents targeting IL-4/IL-13 receptor signaling (dupilumab being the most studied) show promise precisely because they address the upstream cytokine environment rather than anatomy. The practical limitation of this review is its narrative rather than meta-analytic design, meaning effect-size estimates for surgery or biologics on olfactory outcomes remain difficult to benchmark. The central remodeling hypothesis, while scientifically plausible, currently rests on limited human data. For clinicians and patients alike, the key takeaway is that olfactory recovery should be treated as a distinct therapeutic target — not an automatic byproduct of controlling nasal congestion.