Summary 　We clarified that adequate oxygen stress induced by low dose irradiation activates not only chemical biological protective function, such as induction of the synthesis of superoxide dismutase, glutathione peroxidase, and heat shock protein 70, but also the biomembrane function, such as enhanced membrane fluidity and ATPase activity. It is possible that activation of these mechanisms alleviates in vivo oxidation injuries resulting in alleviation of various oxidative damages, which are related to aging and lifestyle diseases, such as symptoms of hepatopathy, diabetes mellitus, and ischemia-reperfusion. Namely, adequate activation of the functions of the living body by low-dose irradiation can contribute to suppressing aging and to preventing or reducing active oxygen species related diseases which are thought to involve peroxidation and have been regarded as the diseases for which radon spa is an effective treatment. Clarification in detail of the mechanisms of these phenomena is required to understand the effects of low dose irradiation or radon inhalation on the functions of the living body, including adaptive response.