# Balneotherapy with the Use of Radon-Sulphide Water: The Mechanisms of Therapeutic Effect
## 2 The Mechanism of the Therapeutic Effect of Radon-Sulphide Water
In diseases with an increased concentration of uric acid in the blood serum, e.g., rheumatic diseases, degenerative joint and spine diseases, and gout, uric acid concentration decreases after a few baths. Under the influence of sulphur, minor contractures are relaxed, muscle and joint stiffness and pain are reduced, the range of joint movement is increased, and overall mobility is improved. With a series of baths, sulphur, calcium, and magnesium compounds enter the body and partially supplement the existing deficiencies. Waters with sulphur content are used both in drinking and bathing treatment. One of the main indications for the use of sulphur waters are degenerative changes in the joints and spine, which are accompanied by pain. It is believed that the sulphur introduced into the body during the treatment is used for the synthesis of chondroitsulphuric acid, which is a component of articular cartilage. Moreover, sulphur is known to be part of the proteoglycans of cartilage, bone, and granulation tissue [9]. Sulphur in therapeutic waters is usually present in the form of sulphide and hydroxulphide ions as well as hydrogen sulphide. Depending on the content of hydrogen sulphide, we distinguish waters with low (\(<\)50 mg/dm\({}^{3}\)), medium (50-100 mg/dm\({}^{3}\)), and high (\(>\)100 mg/dm\({}^{3}\)) concentration of the gas. Sulphur ions penetrate the body through the skin mainly in the form of hydrogen sulphide, thiosulphate, or colloidal sulphur. Hydrogen sulphide penetrates the skin faster than oxygen. In the skin, it is converted into polysulphides, which pass into the blood and then quickly decompose in the tissues into hydrogen sulphide and elemental sulphur. It is excreted from the body with the urine and--in the unchanged form--through the lungs. During bathing, in adults, the absorption of sulphur through the skin is relatively low (about 40 mg in one bath), and the absorption is proportional to its content in the water and the surface of the skin immersed in it. However, in children, this permeability is relatively high. Hydrogen sulphide is particularly well absorbed during bathing, the content of which in the therapeutic water during the treatment itself can be reduced by half, not only due to volatilisation. It was also found that during a bath, hydrogen sulphide penetrates not only through the skin but also through the mucosa of the bronchi, gastrointestinal tract, and the genital tract [9]. Drinking treatment allows for greater sulphur absorption. Studies have shown a rapid absorption of sulphur into the cells. After 20 min, its levels were found to increase in the articular cartilage, bone tissue, vascular wall, and intestinal mucosa. This form of therapy improves absorption and secretion in the intestines, improves gastrointestinal motility and carbohydrate-fat metabolism, and has chologenic, cholepoietic, anti-inflammatory, and desensitising effects [10]. It was found that divalent sulphur penetrating the skin influences immune reactions by inhibiting Langerhans cells and destroys reactive oxygen species (ROS). Sulphur absorbed during a bath inhibits the inflammatory reaction by removing ROS [11]. This mechanism of action probably determines the effective spa therapy of allergic skin diseases and psoriasis [12; 13]. This was confirmed by the studies of [PERSON] et al. They showed the clinical effectiveness of sulphur hot bath therapy in the treatment of atopic dermatitis [14]. Isotopic studies revealed the presence of absorbed sulphur in many tissues, especially the connective tissue, bone tissue, articular cartilage, and in the joint itself. It is estimatedthat a total of 58 mg of sulphur may be absorbed during a bath, taking into account all absorption routes [15]. Bathing in water with sulphur content is also used in the treatment of fibromyalgia [16]. It was found that in the course of a two-week therapy, there was a decrease in pain and other symptoms of the disease as well as an improvement in the assessment of quality of life parameters [17; 18].