H₂ Papers

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Intermittent environmental exposure to hydrogen prevents skin photoaging through reduction of oxidative stress.

間欠的な水素ガス環境曝露による酸化ストレス軽減を介した皮膚光老化の抑制

animal study inhalation positive 1.3%

Abstract

This animal study examined whether intermittent environmental exposure to 1.3% hydrogen gas could mitigate UVA-induced photoaging in mice. A custom apparatus was designed to simulate human daily activity: mice received UVA irradiation for 8 hours (daytime) and hydrogen gas inhalation for 16 hours (nighttime) over a 6-week period. Evaluation of photoaging markers revealed that hydrogen-exposed animals showed reduced epidermal hyperplasia, diminished melanogenesis, fewer senescent cells, and less collagen degradation in the dermis compared with controls. Attenuation of UVA-related DNA damage in the hydrogen group provided indirect evidence of lowered oxidative stress. These findings suggest that long-term, intermittent hydrogen gas exposure during daily life may beneficially affect UVA-induced skin aging processes.

Mechanism

Hydrogen gas is thought to scavenge reactive radicals, thereby reducing oxidative stress and consequently suppressing UVA-induced DNA damage, collagen degradation, melanogenesis, and accumulation of senescent cells in skin tissue.

Bibliographic

Authors
Kiyoi T, Liu SJ, Takemasa E, Hato N, Mogi M
Journal
Geriatr Gerontol Int
Year
2023
PMID
36807963
DOI
10.1111/ggi.14562

Tags

Disease:aging / frailty (37) skin disease (34) Delivery:inhalation delivery (196) Mechanism:hydroxyl radical scavenging (352) lipid peroxidation (238) 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.

See also:

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