The external crenotherapy also called balneotherapy or hydroterapy is a thermal cure technique that can be performed in spas with mineral water for the promotion of health and the prevention or treatment of certain diseases and is becoming increasingly popular in many countries, especially in South America, East Asia and Africa.

In many European countries the teaching of balneotherapy is included in courses of medical disciplines and treatments. Employing thermal mineral waters is expected to fully enter into traditional medicine and is therefore provided by the national health services. Many studies, in fact, report the physiological and/or therapeutic effects obtained with the external application of thermal mineral waters including those on cardiovascular, respiratory, nervous, musculoskeletal, immune systems and eye, skin and hair. This technique is widely used for example in diseases such as rheumatoid arthritis, fibromyalgia, etc., although they have yet to clarify many issues regarding the mechanisms by which hydrotherapy can act on these disorders. Following the conclusions of a study that involved 10 nations with a total of 2650 spas, recently the World Health Organization (WHO) introduced balneotherapy among the strategies of traditional medicine 2014-2023 thus affirming that the thermal medicine like those traditional medicines can be considered an evidence-based medicine. The investigation revealed that of all the diseases considered balneotherapy is used as the main treatment for 29% of arthritic problems in various body sites, 14% for rheumatic problems and 17.5% for respiratory diseases, and those of the digestive system.

The use of balneotherapy with thermal mineral water in swimming pools requires from a sanitary point of view a particular surveillance since traditional chemical disinfection systems can’t be used to disinfect water because they alter the peculiar characteristics of mineral water. The quality standards in this case are maintained by natural systems such as the frequent replacement of the water used in swimming pools, although this is a rather complex method for large tanks, or emptying and cleaning of the pool's surfaces.

Some studies have demonstrated the presence of filamentous fungi in drinking water or water distribution systems in hospitals such as dialysis water and their ability to resist chlorine or other chemical disinfectants therefore If pathogenic filamentous fungi are present in water they could represent a risk of microbial infection, in this case the water could act as a vehicle of transmission of various infective agents such as Epidermophyton spp and Trichophyton spp which may cause hair and nail infections called dermatophytosis. The UV-C radiation (254 nm) is applied widely for a long time in the disinfection of water such as those destined for drinking, hospital systems or swimming pools since it offers the advantage of having a rapid action, not forming byproducts (DBP) and having low maintenance costs. In this respect it was shown that UV radiation is able to have a wide spectrum of action with a biocidal effect on bacteria, viruses, parasites and fungi. In addition the microbicidal effectiveness of the UV radiation has been well documented but not as well as its fungicidal activity in the water of swimming pools, including those that employ thermal water. Although there are many documents concerning the presence of fungi or their survival in the pool water treated with chlorine, including dermatophytes, still few data are available regarding their presence in the thermal water used in swimming pools.

The purpose of this study was to demonstrate the validity of the use of the UV radiation as an alternative method of thermal disinfection of swimming pool water containing the microbiological risk induced by the presence of dermatophytes. The strains selected for the study, all of clinical origin, were isolated from nail and skin infections and they consisted of Epidermophyton floccosum, Trichophyton mentagrophytes, Trichophyton rubrum, Trichophyton schoenleinii, Trichophyton tonsurans, and Trichophyton violaceum.

The experiment was conducted in a pilot plant system by contaminating the water, maintained at 30°C, with the fungi at a concentration of 2 x 103 CFU/ml, the plant was provided with a lamp (Philips Philips TUV PL-L 18 W, 4-pin - low pressure mercury lamp) submerged in a thermal mineral. It the survival of fungi with the lamp was evaluated with the following activities Rates: 0 (not irradiated control) 10, 20, 30, 60 and 120 s corresponding to doses of 16, 32, 48.1, 96.2 and 192.4 mJ/cm². In parallel we also evaluated the survival times of fungi in the same water but without the treatment with the UV radiation. The results obtained in this work showed that within brief exposure times one can achieve significant reductions in the concentration of fungi and that within 60 sec of exposure time only T. tonsurans, in these conditions, is able to resist even though with a significant reduction equivalent 3.28 log than the initial concentration. While exposures between 60 and 120 s are able to completely eliminate the more resistant dermatophytes. It was also demonstrated that in the absence of this alternative disinfectant treatment with UV radiation, some of the tested fungi, such as T. rubrum and T. mentagrophytes have a survival capacity in thermal water up to 40 and 70 days, respectively.

Fungi generally have a greater resistance capacity of other microorganisms such as bacteria against UV radiation in particular those containing melanin pigments as in this case the dermatophytes. In addition, these pigments are able to also play an important pathogenic role.

In conclusion, our results demonstrate the effectiveness of disinfection through the use of UV radiation in preventing microbiological risk presented by the presence of fungi dermatophytes in the waters of the thermal pools used in balneotherapy.