Narrowband ultraviolet B (NB-UVB) phototherapy has been used clinically for the treatment of atopic dermatitis (AD). Therefore, NB-UVB phototherapy could also be effective for the treatment of allergic rhinitis (AR), because AR is also a Th2-dominant disease like AD. Recently, light-emitting diodes (LEDs) that emit selective UVB spectra at a wavelength of 310 nm (NB-UVB) have been developed, that are small enough for intranasal phototherapy. In order to develop NB-UVB phototherapy for AR, we first examined the effects of NB-UVB irradiation on the H1R gene expression in HeLa cells. We demonstrated that low-dose NB-UVB irradiation reversibly suppressed PMA-induced upregulation of H1R mRNA in a wavelength-specific and dose-dependent manner, without inducing apoptosis of the HeLa cells. We then conducted an in vivo study using toluene 2,4-diisocyanate (TDI)-sensitized rats, an animal model of AR. We demonstrated that intranasal NB-UVB pre-irradiation suppressed TDI-induced upregulation of H1R mRNA in the nasal mucosa in a dose-dependent manner, without induction of DNA damage, causing suppression of the TDI-induced nasal symptoms in this animal model of AR. These findings suggest that low-dose NB-UVB phototherapy could be effectively and safely applied for the treatment of AR. Finally, we have developed a prototype of an NB-UVB phototherapy device and demonstrated its safety in phase I and early phase II clinical trials.
