Living bodies may experience oxidative stress induced by reactive oxygen species and heavy metal ions, which may damage components in the body and cause aging and disorders. In addition to the known defense systems against oxidative damage, the author describes new defense systems. Lipid peroxidation in living bodies, which has hitherto been thought to increase oxidative damage, was found to attenuate oxidative stress-induced DNA damage. Red blood cells become senescent due to oxidative stress during circulation, where membrane band 3 becomes aggregated to anti-band 3 IgG and macrophages attached through poly-N-acetyllactosaminyl sugar chains, and the sugar chain attachment to macrophages is stimulated by oxidative stress in macrophages. Oxidized protein hydrolase that preferentially hydrolyzes proteins damaged by oxidative stress was newly discovered, which may play an important role in saving cells from oxidative damage.