Olfactory cleft inflammation is present in seasonal allergic rhinitis and is reduced with intranasal steroids

Allergic rhinitis (AR) is commonly associated with olfactory loss, although the mechanism is not well studied. This study was designed to determine the effect of mometasone furoate (MF) on olfactory loss in seasonal AR (SAR) and study its effect on inflammation in the olfactory region.

We performed a randomized, double-blind, placebo-controlled, parallel clinical trial in 17 patients with SAR who had symptoms of impaired olfaction. Subjects received MF or placebo for 2 weeks during their allergy season. Before and after treatment, we measured nasal peak inspiratory flow (NPIF), chemosensory quality of life, and objective olfactory function (the University of Pennsylvania Smell Identification Test). Additionally, nasal cytology samples were obtained from each visit, and a unilateral endoscopic biopsy specimen of the olfactory epithelium was obtained at the end of the study and scored for inflammation.

Treatment with MF was associated with improved nasal symptoms (p < 0.015), NPIF (p < 0.04), reduced nasal inflammation (p < 0.05), and chemosensory-specific quality of life (p < 0.03). Histological analysis of the olfactory region reveals fewer eosinophils in the MF group when compared with placebo (p < 0.012). We found no improvement in objective olfactory function (p > 0.05).

The use of MF in SAR is associated with reduced eosinophilic inflammation in the olfactory region and improved symptoms of AR. The presence of eosinophils in the olfactory area in SAR may indicate a direct, deleterious effect of inflammation on olfactory epithelium in this disease. In this study we show that inflammation in SAR can affect the olfactory cleft, implicating a direct role for allergic inflammation in smell loss. Treatment with intranasal steroids is associated with decreased inflammation in the olfactory region in humans. This treatment is also associated with improved olfactory quality of life.