H₂ Papers

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The impact of hydrogen inhalation therapy on blood reactive oxygen species levels: A randomized controlled study.

水素吸入が血中活性酸素種レベルに与える影響：無作為化対照試験

human randomized controlled trial inhalation positive

Abstract

Reactive oxygen species (ROS) participate in normal physiological functions, yet an excess relative to antioxidant capacity leads to oxidative stress implicated in various pathological conditions. Molecular hydrogen possesses selective antioxidant properties and high membrane permeability, making it a candidate for reducing oxidative burden. This randomized controlled trial enrolled 37 individuals with elevated blood ROS levels (d-ROMs > 350 U.CARR) and assigned them to either a hydrogen inhalation group or a non-intervention control group. Blood ROS concentrations were assessed immediately after the intervention and again at 24 hours. The hydrogen inhalation group exhibited a statistically significant decrease in circulating ROS compared with controls, supporting the capacity of hydrogen gas inhalation to reduce systemic oxidative stress markers.

Mechanism

Molecular hydrogen, owing to its small molecular size and selective reactivity, is thought to neutralize excess reactive oxygen species without disrupting normal redox signaling, thereby lowering circulating oxidative stress markers.

Bibliographic

Authors
Chair M, AlAani H, Lafci Fahrioglu S, Ben Hamda C, Fahrioglu U, Degheidy T
Journal
Free Radic Biol Med
Year
2024
PMID
38996821
DOI
10.1016/j.freeradbiomed.2024.07.010

Tags

Delivery:inhalation delivery (196) Mechanism:antioxidant enzymes (423) hydroxyl radical scavenging (352) oxidative stress (899) reactive oxygen species (774)

Delivery context

In air, molecular hydrogen is reported to be combustible across approximately **4% (LFL, lower flammability limit) to 75% (UFL, upper flammability limit)**. Among high-concentration hydrogen inhalers, 66% output sits inside this range, and even pure-hydrogen (100%) output forms a 4–75% concentration-gradient layer at the device–air boundary (the UFL 75% paradox). Engineering principle would therefore call for operation below LFL (the classical 4%); that figure, however, was measured under closed, pre-mixed, static conditions. For the open, dynamic inhalation environment, the empirical value reported in the literature is **10%**, which is the figure referenced in practice as the operating ceiling. The 66% / 100% output devices are recorded in the Japanese Consumer Affairs Agency accident-information database, and from these considerations are not recommended.

→ Evidence by delivery route

Safety notes

In air, molecular hydrogen is reported to be combustible across approximately **4% (LFL, lower flammability limit) to 75% (UFL, upper flammability limit)**. Among high-concentration hydrogen inhalers, 66% output sits inside this range, and even pure-hydrogen (100%) output forms a 4–75% concentration-gradient layer at the device–air boundary (the UFL 75% paradox). Engineering principle would therefore call for operation below LFL (the classical 4%); that figure, however, was measured under closed, pre-mixed, static conditions. For the open, dynamic inhalation environment, the empirical value reported in the literature is **10%**, which is the figure referenced in practice as the operating ceiling. The 66% / 100% output devices are recorded in the Japanese Consumer Affairs Agency accident-information database, and from these considerations are not recommended.

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