Smell and the sinuses: Mechanisms, evaluation, and management of olfactory dysfunction in sinonasal disease.

BACKGROUND

Olfactory dysfunction is a common and clinically significant manifestation of inflammatory sinonasal disease.

OBJECTIVE

To summarize the mechanisms, evaluation, and management of smell loss in sinonasal disease, with an emphasis on practical clinical approaches.

DATA SOURCES: Peer-reviewed literature, consensus guidelines, and major position statements related to olfactory dysfunction, chronic rhinosinusitis, nasal polyposis, allergic rhinitis, and type 2 inflammatory diseases.

STUDY SELECTION: Relevant clinical trials, systematic reviews, meta-analyses, and guideline-based recommendations were selected based on their clinical relevance.

RESULTS

Olfactory dysfunction in sinonasal disease arises through conductive mechanisms that impair odorant delivery to the olfactory cleft and inflammatory mechanisms involving cytokine-driven neuroepithelial injury; these pathways frequently coexist. Type 2 inflammation-mediated by eosinophils, interleukin (IL)-4, IL-5, and IL-13-plays a central role in chronic rhinosinusitis with nasal polyposis and aspirin-exacerbated respiratory disease, disrupting epithelial integrity and impairing neuronal regeneration. Clinical evaluation integrates targeted history, nasal endoscopy with olfactory cleft assessment, validated psychophysical smell testing, and selective imaging. Evidence-based management includes intranasal corticosteroids, saline irrigation, endoscopic sinus surgery for medically refractory disease, and biologic therapies, which demonstrate rapid and sustained olfactory improvement with steroid-sparing effects. Septoplasty and turbinate reduction address structural contributors. Olfactory training provides additional benefit as a low-risk adjunct across etiologies.

CONCLUSION

Olfactory dysfunction is a key manifestation of inflammatory sinonasal disease that reflects the interplay between mechanical obstruction and immunologic injury. A structured diagnostic and therapeutic approach enables the identification of reversible causes, the selection of targeted therapies, and the optimization of olfactory outcomes.