Hydrogen (H2) is a strong anti-oxidant with anti-inflammatory and anti-allergic effects. H2 has a number of advantages as a potential antioxidant. First, it has favorable distribution characteristics with its own physical ability to penetrate biomembranes and diffuse into the cytosol. Excessive oxidative damage is a major factor because the mitochondrial respiratory chain is a significant source of damaging reactive oxygen species; however, despite the clinical importance of mitochondrial oxidative damage, antioxidants have been of limited therapeutic success. This may be because antioxidants are not selectively taken up by mitochondria. As H2 effectively reaches the nucleus and mitochondria, the protection of nuclear DNA and mitochondria suggests preventive effects on lifestyle-related diseases, cancer and the aging process. Moreover, H2 passes through the blood brain barrier, although most antioxidant compounds cannot; this is also an advantage of H2. H2 decreased the expressions of pro-inflammatory factors: TNF-alpha, IL-6, IL-1beta, CCL2, IL-10, TNF-alpha, IL-12, ICAM-1, HMGB-1, NF-kappaB, PGE2 H2 up-regulates: PCNA, bFGF, HGF, IFN-gamma H2 down-regulation: i-NOS, VEGF H2 inhibited the phospahorylations of: MEK, p38, ERK, JNK, Lyn, Syk, PLC gamma 1, gamma 2, Akt, ERK1/2, JNK, p38, cPLA2, ASK1 Methods to ingest or consume H2: Inhaling hydrogen gas Drinking H2-dissolved water (hydrogen water) Taking a hydrogen bath Injecting H2-dissolved saline (hydrogen saline) Dropping hydrogen saline onto the eye Increasing the production of intestinal H2 by bacteria Recent Progress Toward Hydrogen Medicine: Potential of Molecular Hydrogen for Preventive and Therapeutic Applications.