# 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


## 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](https://pubmed.ncbi.nlm.nih.gov/36807963/)
- **DOI**: [10.1111/ggi.14562](https://doi.org/10.1111/ggi.14562)
- **Study type**: animal study
- **Delivery route**: inhalation
- **Effect reported**: positive
- **H2 concentration**: 1.3%

## Delivery context

For inhalation applications of molecular hydrogen, the lower flammability limit (LFL) deserves careful handling. The classical 4% figure applies to closed-system mixtures; the practical inhalation-environment threshold is 10%. Even pure-hydrogen output (the UFL 75% paradox) passes through the flammable range at the air–gas boundary. High-concentration (66% / 100%) inhalers are documented in the Japanese Consumer Affairs Agency accident-information database and are not recommended.

## Safety notes

For inhalation applications of molecular hydrogen, the lower flammability limit (LFL) deserves careful handling. The classical 4% figure applies to closed-system mixtures; the practical inhalation-environment threshold is 10%. Even pure-hydrogen output (the UFL 75% paradox) passes through the flammable range at the air–gas boundary. High-concentration (66% / 100%) inhalers are documented in the Japanese Consumer Affairs Agency accident-information database and are not recommended.

See also:
- [Inhalation concentration and LFL / UFL](https://h2-papers.org/en/safety-notes/inhalation-concentration)
- [Consumer Affairs Agency accident cases](https://h2-papers.org/en/safety-notes/accident-cases)
- [LFL / UFL terminology](https://h2-papers.org/en/safety-notes/lfl-ufl-explained)
- [Inhalation safety threshold lineage](https://h2-papers.org/en/safety-notes/lineage)

---

> **Cite as**: H2 Papers — PMID 36807963. https://h2-papers.org/en/papers/36807963
> **Source**: PubMed PMID [36807963](https://pubmed.ncbi.nlm.nih.gov/36807963/)