Randomized, crossover clinical efficacy trial in humans and mice on tear secretion promotion and lacrimal gland protection by molecular hydrogen

The incidence of dry eye disease is increasing worldwide because of the aging population and increasing use of information technology. Dry eye disease manifests as tear-layer instability and inflammation caused by osmotic hypersensitization in tear fluids; however, to our knowledge, no agent that treats both pathologies simultaneously is available. Molecular hydrogen (H 2 ) is known to be effective against various diseases; therefore, we aimed to elucidate the effects of H 2 on tear dynamics and the treatment of dry eye disease. We revealed that administering a persistent H 2 -generating supplement increased the human exhaled H 2 concentration ( p < 0.01) and improved tear stability ( p < 0.01) and dry eye symptoms ( p < 0.05) significantly. Furthermore, H 2 significantly increased tear secretion in healthy mice ( p < 0.05) and significantly suppressed tear reduction in a murine dry eye model ( p = 0.007). H 2 significantly and safely improved tear stability and dry eye symptoms in a small exploratory group of 10 human subjects, a subset of whom reported dry eye symptoms prior to treatment. Furthermore, it increased tear secretion rapidly in normal mice. Therefore, H 2 may be a safe and effective new treatment for dry eye disease and thus larger trials are warranted.