Therapeutic Potential of Chitosan Nasal Gel in Addressing Olfactory Dysfunction: A Clinical Trial and Mechanistic Study

BackgroundOlfactory dysfunction significantly impacts daily life, affecting safety, appetite, and sensory enjoyment. Olfactory receptor neurons (ORNs) are essential for odor detection, but environmental exposure can lead to dysfunction. Regeneration of these neurons is crucial for maintaining olfactory function, and elevated calcium levels in nasal mucus are linked to this dysfunction.ObjectiveThe study evaluated chitosan nasal gel for persistent olfactory dysfunction lasting over 6 months, focusing on ORNs regeneration and reduced calcium levels in nasal mucus.MethodsA randomized, double-blind trial included 215 participants with persistent olfactory dysfunction lasting over 6 months. Participants were divided into two groups: 116 received nasal chitosan gel, and 99 received a control sodium chloride gel. Over 3 months, 11 participants in the chitosan group and 9 in the control group were lost to follow-up. Olfactory function was assessed with the Sniffin' Sticks test, and calcium levels were measured before and after treatment.ResultsPatients treated with chitosan nasal gel showed an increased composite threshold, discrimination, identification (TDI) score, indicating improved olfactory function. Discrimination and identification scores improved, while threshold scores showed no significant change. Notably, while the total TDI score improved by 4.55 points, it did not reach the threshold for clinical significance (5.5 points). Furthermore, chitosan nasal gel significantly reduced calcium levels in nasal secretions compared to the control group. No improvement was observed in the placebo group, likely due to the strict inclusion criteria targeting individuals with treatment-resistant olfactory dysfunction persisting over 6 months.ConclusionThis small-scale pilot study highlights the potential of chitosan nasal gel to improve specific domains of olfactory dysfunction and reduce nasal calcium levels. However, further studies with larger sample sizes, diverse populations, and longer follow-up periods are required to confirm these preliminary findings.