Abstract: We included four studies (five publications) involving 302 participants with idiopathic non-allergic rhinitis. All the included studies described patients with moderately severe, idiopathic non-allergic rhinitis who were between the ages of 16 and 65. Studies had follow-up periods ranging from four to 38 weeks. The overall risk of bias in the studies was either high or unclear (two studies had overall high risk of bias, while two others had low to unclear risk of bias). Using the GRADE system we assessed the evidence as being of low to moderate quality. A meta-analysis was not possible, given lack of similarity of the reported outcomes. Two studies compared capsaicin with placebo. One study reported that capsaicin resulted in an improvement of overall nasal symptoms (a primary outcome) measured on a visual analogue scale (VAS) of 0 to 10. There was a mean difference (MD) of -3.34 (95% confidence interval (CI) -5.24 to -1.44), MD -3.73 (95% CI -5.45 to -2.01) and MD -3.52 (95% CI -5.55 to -1.48) at two, 12 and 36 weeks post-treatment, respectively. Another study reported that, compared to placebo, capsaicin (at 4 µg/puff) was more likely to produce overall symptom resolution (reduction in nasal blockage, sneezing/itching/coughing and nasal secretion measured with a daily record chart) at four weeks post-treatment (a primary outcome). The risk ratio (RR) was 3.17 (95% CI 1.38 to 7.29). One study compared capsaicin to budesonide (an intranasal corticosteroid). This study found that patients treated with capsaicin had a better overall symptom score compared to those treated with budesonide (MD 2.50, 95% CI 1.06 to 3.94, VAS of 0 to 10). However, there were no differences in the individual symptom scores for headache, postnasal drip, rhinorrhoea, nasal blockage, sneezing and sore throat assessed during the last three days of a four-week treatment. One study compared two different regimens of capsaicin administration: five treatments in one day versus five treatments given every two to three days during two weeks. Using daily record charts, the study reported significant improvement of individual symptom scores for rhinorrhoea in patients treated five times per day, however numerical data were not presented. There were no improvements in the other outcomes: rhinorrhoea, nasal obstruction, sneezing and overall nasal symptoms, measured on a VAS. Finally, one of these studies also compared three doses of capsaicin (to placebo). Patients treated with a 1 µg versus 4 µg per puff dose of capsaicin had a worse daily record chart overall symptom score resolution (RR 0.63, 95% CI 0.34 to 1.16). Only one study attempted to measure adverse effects (a primary outcome), however due to methodological issues with the assessment we are unable to draw any conclusions. We sought to include other secondary outcomes (e.g. quality of life measures, treatment dropouts, endoscopic scores, turbinate or mucosal size, cost of therapy), but none of these were measured or reported in the included studies. Capsaicin may be an option in the treatment of idiopathic non-allergic rhinitis. It is given in the form of brief treatments, usually during the same day. It appears to have beneficial effects on overall nasal symptoms up to 36 weeks after treatment, based on a few, small studies (low-quality evidence). Well-conducted randomised controlled trials are required to further advance our understanding of the effectiveness of capsaicin in non-allergic rhinitis, especially in patients with non-allergic rhinitis of different types and severity, and using different methods of capsaicin application.

Plain-language summary: We included four studies involving 302 patients with idiopathic non-allergic rhinitis. All the included studies described patients with moderately severe idiopathic non-allergic rhinitis, who were between the ages of 16 and 65. The studies had a follow-up ranging from four to 38 weeks after treatment. Individually, the studies reported that the overall function of the nose in patients with non-allergic rhinitis improved when treated with capsaicin compared to placebo. Capsaicin also seems to work better than another common type of nasal medication, budesonide (a steroid). The best knowledge that we have on capsaicin treatment supports giving it five times in one day, and to use doses of at least 4 micrograms in each puff. We could not combine the results together. The included studies did not have sufficient information to allow us to draw a conclusion about side effects. We also wanted to include other outcomes (e.g. quality of life measures, treatment dropouts, endoscopic scores, turbinate or mucosal size, cost of therapy), but none of these were measured or reported in the included studies. Overall, we judged the quality of the evidence to be of low to moderate quality. The evidence is up to date to June 2015. Given that many other options do not work well in non-allergic rhinitis, capsaicin is a reasonable option to try under physician supervision.