Background: Capsaicin has been shown previously to reduce nasal complaints in patients with a non-allergic non-infectious perennial rhinitis. Proposed pathophysiological mechanisms for non-allergic non-infectious perennial rhinitis include a chronic inflammatory disorder of an antigenic or neurogenic nature as well as the possibility of a functional neuronal disorder. We hypothesized that the beneficial effect of capsaicin might be the result of a down-regulation of inflammation (by a reduction of inflammatory cells) or through modulation of neural tissue density.
Methods: Patients were treated with either a placebo or capsaicin spray solution delivering 0.15 mg of capsaicin per nostril once every second or third day for a total of seven treatments. Both sides were treated each visit. Biopsies were taken before and 2 weeks, 3 months and 9 months after the treatment period. Immunohistochemical staining of the biopsy specimen was performed to ascertain the effect of treatment on immunocompetent cell densities (quantitative) and neural tissue densities (semi-quantitative) in the nasal mucosa.
Results: Nasal complaints were significantly reduced in the capsaicin-treated group. The number of CD1+, CD25+, CD3+, CD68+, BMK13+, IgE+, tryptase+, and chymase+ cells did not significantly differ between capsaicin and placebo group. No significant differences between both groups were found in pan-neurogenic staining of nasal mucosa using neurofilament and synaptophysine.
Conclusion: Capsaicin aqueous nasal spray has previously been shown to reduce nasal complaints without affecting cellular homeostasis or overall neurogenic staining up to 9 months after treatment. Immunocompetent cells are not involved in non-allergic non-infectious perennial rhinitis.