The long-term effects of capsaicin aqueous spray on the nasal mucosa

Background Capsaicin has been shown previously to reduce nasal complaints i n patients with a non-allergic non-infectious perennial rhinitis. Proposed pathophysiological mechanisms for non-allergic non-infectious perennial rhi nitis include a chronic inflammatory disorder of an antigenic or neurogenic nature as well as the possibility of a functional neuronal disorder. We hy pothesized 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 solu tion 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. B iopsies were taken before and 2 weeks, 3 months and 9 months after the trea tment period. Immunohistochemical staining of the biopsy specimen was perfo rmed to ascertain the effect of treatment on immunocompetent cell densities (quantitative) and neural tissue densities (semi-quantitative) in the nasa l mucosa. Results Nasal complaints were significantly reduced in the capsaicin-treate d group. The number of CD1(+), CD25(+), CD3(+), CD68(+), BMK13(+), IgE(+), tryptase(+), and chymase(+) cells did not significantly differ between caps aicin and placebo group. No significant differences between both groups wer e found in pan-neurogenic staining of nasal mucosa using neurofilament and synaptophysine. Conclusion Capsaicin aqueous nasal spray has previously been shown to reduc e nasal complaints without affecting cellular homeostasis or overall neurog enic staining up to 9 months after treatment. Immunocompetent cells are not involved in non-allergic noninfectious perennial rhinitis.