Effects of Inhalation of Hydrogen Gas on Allergic Conjunctivitis Model Mice

Purpose: Over the past decades, the prevalence of ocular allergies has increased worldwide. Molecular hydrogen is the lightest chemical element, and in recent years, there have been multiple reports on its therapeutic effects. Animal studies have also reported the effects of hydrogen gas on various models of inflammation and circulatory disorders. Methods: In this study, we investigated the effects of hydrogen gas inhalation in a mouse model of allergic conjunctivitis. Mice were sensitized by intraperitoneal injection of ovalbumin. Local sensitization was performed once daily by instilling ovalbumin in both eyes. Conjunctivitis model mice were challenged with antigens, and eye-scratching behavior induced by antigen stimulation was evaluated. The hydrogen gas exposure group was exposed to hydrogen gas after the antigen challenge. In addition, the same mice were exposed to hydrogen gas after antigen challenge, and the number of eosinophils in the tears was evaluated. Results: An increase in eye-scratching behavior induced by antigen was observed. Hydrogen gas suppressed the increase in eye-scratching behavior. Moreover, hydrogen gas inhibited the increase in eosinophil count in tears. Conclusions: Active oxygen has a profound effect on itching and eosinophilic function. Therefore, it is thought that inhalation of hydrogen gas suppresses itching of the eye and the migration of eosinophils into the tissue by removing reactive oxygen species. Inhalation of hydrogen gas suppressed the symptoms of allergic conjunctivitis.