High-flow hydrogen inhalation might suppresses the immune function of middle-aged participants: a self-controlled study.

Hydrogen inhalation therapy has been proven to be safe and effective in disease treatment in multiple clinical reports, but the gas flow rates used in different studies vary greatly. Since there is no upper limit for the safe concentration of hydrogen, this study tested the effects of high-flow (not high concentration) hydrogen inhalation on immune function. From October 2019 to January 2020, 20 adult participants (31-60 years old) were enrolled in a self-controlled study to check the immune function in peripheral blood lymphocyte subsets before and after a 2-week hydrogen inhalation protocol. The participants inhaled hydrogen for 2 or 4 hours each day. After 2 weeks of hydrogen inhalation, statistically significant changes were observed in follicular helper T cells, helper and cytotoxic T cells, natural killer and natural killer T cells, and gamma delta T cells, generally suggesting a decrease in their proportions. These results show that high-flow hydrogen inhalation has an inhibitory effect on the immune function of healthy participants. The study protocol received ethical approval from the Ethics Committee of Fuda Cancer Hospital, Jinan University on December 7, 2018 (approval No. Fuda20181207).