Research review: Molecular hydrogen for wound healing and tissue regeneration

Wound healing unfolds in four overlapping phases: hemostasis, inflammation, proliferation and tissue remodeling. Each phase depends on a tightly regulated burst of reactive oxygen species — too little, and pathogens persist; too much, and the wound stalls in chronic inflammation.

Chronic non-healing wounds — diabetic ulcers, pressure injuries, radiation wounds — share a common signature: elevated TNF-α and IL-1β, excessive ROS, impaired angiogenesis and reduced collagen deposition. Aging, obesity and immunosuppressive therapy compound the problem by lowering growth-factor production and angiogenic capacity.

H₂ is the smallest molecule in biology. It diffuses freely across membranes, accumulates in subcellular compartments, and reacts preferentially with the two most cytotoxic ROS — ·OH (converted to water) and ONOO⁻ (converted to nitrite and water). It does not interfere with H₂O₂ or superoxide signalling needed for normal repair.

This selectivity is the central pharmacological argument for hydrogen over broad-spectrum antioxidants, which have repeatedly failed in chronic wound trials by blunting the redox signals required for healing.

Hydrogen activates the Nrf2 transcription factor, which up-regulates endogenous antioxidant enzymes — superoxide dismutase (SOD), catalase and glutathione peroxidase (GSH-Px). The cell's own defence system is thereby strengthened, an effect that persists after the H₂ exposure ends.

In parallel, H₂ down-regulates the NF-κB inflammatory cascade and reduces TNF-α and IL-1β levels — the precise signals that hold chronic wounds in the inflammatory phase.

Hemostasis: H₂ does not interfere with platelet aggregation or fibrin formation but limits oxidative damage to surrounding tissue.

Inflammation: reduces neutrophil over-recruitment and macrophage-driven cytokine storms.

Proliferation: supports fibroblast migration, collagen deposition and angiogenesis through VEGF-related signalling.

Remodeling: modulates matrix metalloproteinase activity for better collagen organisation and reduced scarring.

The review surveys three feasible administration routes: inhalation of H₂ gas (typically 1–4% in oxygen or air), drinking hydrogen-rich water and bathing in hydrogen-dissolved water. Each route delivers measurable systemic H₂ exposure, with inhalation producing the highest sustained tissue concentrations.

Safety has been documented across hundreds of studies — H₂ is non-toxic up to flammability thresholds far above clinical dosing, with no observed adverse drug interactions.