Spa therapy in Misasa (Tottori Prefecture, Japan) is renowned worldwide for its radon therapy (particularly high-concentration radon hot-air bath therapy) along with mine therapy in Bad Gastein (Austria) and Montana (USA). Radon therapy is indicated for diseases related to the respiratory system, pain, digestive disorders, chronic degeneration, and aging caused by reactive oxygen species; however, most of these indications are based on empirical prescriptions. To address this, the authors have been conducting basic research to experimentally and mathematically identify significant radon and its progeny exposure pathways and their related behaviors in the body. The aim is to quantitatively evaluate the relationship between the biological reactions caused by radon inhalation and the absorbed doses in tissues and organs, and to elucidate new mechanisms related to these indications. Therefore, the mechanisms are being elucidated in terms of a series of moderate physiological stimuli caused by small amounts of oxidative stress induced by radon inhalation. Specifically, radon inhalation enhances antioxidant, immune regulation, and damage-repair functions; promotes anti-inflammation, hormone secretion, and circulatory metabolism; and induces apoptosis and heat shock proteins. New indications have been suggested, including inflammatory and neuropathic pain, inflammatory edema, gastric mucosal damage, ulcerative colitis, hyperuricemia, type 1 diabetes, liver and kidney damage, transient cerebral ischemia, and depression. Furthermore, combining radon therapy with antioxidants and therapeutic agents has been suggested to synergistically enhance the disease-suppressing effects of the therapy. Further clinical verification of the combined effects of radon therapy and conventional treatments is required to reduce the dosage of drugs that cause severe side effects.

  A large number of patients are treated in various countries with the traditional radon spa therapy. Adequate oxygen stress induced by radon inhalation activates chemical biological protective functions, such as induction of the synthesis of superoxide dismutase (SOD) and glutathione peroxidase. We previously reported that radon inhalation elevated antioxidant enzymes in patients with bronchial asthma and osteoarthritis 1), 2). Objectives: Although many clinical studies have been reported, the reason why radon inhalation results in positive effects is still unclear. To elucidate the probability that activation of chemical biological protective functions alleviates various oxidation injuries, we studied the mechanisms of the effects of radon using small animals. Methods: To examine whether radon inhalation activates antioxidative functions in mice, we developed a new facility for exposing small animals to radon and examined SOD activity, which is an antioxidative enzyme, in plasma, liver, pancreas, heart, thymus, kidney, brain, small intestine, lung, and stomach of mice. Mice were exposed to radon at a concentration of 250, 500, 1000, 2000, or 4000 Bq/m3 for 0.5, 1, 2, 4, or 8 days. Results: It was shown that continuous exposure to radon increases SOD activity in most organs of mouse. In addition, our data suggested some new indications for radon treatment3). Next, we assessed whether radon inhalation provided protection from carbon tetrachloride (CCl4)-induced hepatic and renal damage in mice. Results showed that radon inhalation inhibited CCl4-induced hepatic and renal damage in mice due to activation of antioxidative functions in liver and kidney4). Although hepatic and renal damage are not the main indication for radon therapy, radon inhalation mitigates liver and kidney damage due to activation of antioxidative functions in liver and kidney. This antioxidative effect against CCl4-induced hepatopathy is comparable to treatment with ascorbic acid (vitamin C) at a dose of 500 mg/kg weight or α-tocopherol (vitamin E) treatment at a dose of 300 mg/kg weight and is due to activation of antioxidative functions5). We also suggested radon inhalation inhibits streptozotocin (STZ)-induced type I diabetes in mice due to activation of antioxidative functions in pancreas. Conclusion: Thus, radon inhalation very likely activates the defense systems in the body, and therefore, contributes to preventing or reducing reactive oxygen species (ROS)-related injuries, which are thought to involve peroxidation.

Purpose: We have previously reported the physiological and biochemical effects of bath salts. In this study, we used bath additive containing artificial carbon dioxide and sodium chloride (S bath additive), and the acute effects of bathing once with S bath additive and chronic effects of daily bathing with S bath additive for 15 consecutive days were compared with the effects of bathing once in plain water. Improvement in 10 symptoms was investigated using a 5-point verbal rating scale (VRS). Methods: Nine patients aged 51-82 years (mean, 66.6 years) with cold intolerance and lower leg pain were treated with balneotherapy. Whole-body bathing at 40°C was performed for 10 min daily (day 1, bathing in plain water; days 2-16, bathing with S bath additive). On days 1, 2, and 16, changes in patient’s subjective symptoms were evaluated using a VRS ranging from -1 to +3. Results: Compared with bathing once in plain water, bathing once with S bath additive was improvement of coldness, body warmth, blood circulation promotion, limb warmth, lightness of foot, and coldness in limbs. Daily bathing with S bath additive for 15 days significantly improved all symptoms compared with bathing in plain water. A comparison between single and daily bathing with S bath additive showed that relieving fatigue and lumbago were significantly improved after consecutive bathing, demonstrating the benefits of long-term usage. Discussion: Bathing once with S bath additive had acute effects on symptoms associated with peripheral circulation, such as coldness in limbs, body warmth, and limb warmth. Daily bathing with S bath additive improved bone- and joint-related symptoms, such as lumbago and shoulder stiffness, demonstrating that the chronic effects of S bath additive differ from the acute ones. These results are consistent with previous studies on natural hot springs which found that the efficacy of short-term treatment was distinct from that obtained after >2 weeks of treatment.

Design : A pilot, comparative study was conducted. Background : Heat wraps using bentonite (HWb) are commonly used in thermotherapy. In the Okayama University Misasa Medical Center, heat wraps using mud (HWm) produced by mixing soil with boiling water have also been used. The subjective thermal effects of HWm on patients with osteoarthritis of the knee have been reported. However, the objective thermal effects of HWm have not been examined. As such, the physicochemical thermal effects of HWm were analyzed and compared with those of HMb. Methods : The thermal effects of HWm and HWb were investigated regarding heat radiation, conduction, capacity and moisture content. Heat radiation and conduction were measured by changes in temperature of the heat wraps, in addition heat conduction was also assessed by blood flow in body surfaces (N=7). Heat capacity and moisture content were measured with a Differential Scanning Calorimeter. Results: Heat radiation and heat conduction of HWm were significantly greater than those of HWb (p<0.001). The specific heat capacity of HWm was 2.0 J/g/°C, and was 1.7 J/g/°C for HWb. Moisture content of HWm and HWb were 0.6 mg/g and 0.3 mg/g, respectively. Conclusion : Heat radiation, conduction and capacity of HWm are superior to those of HWb. Moreover, the moisture content in HWm is greater than that of HWb. These results indicate that the thermal effects of HWm would have more be physicochemical usefulness.