Water-Based Therapies of Bhutan: Current Practices and the Recorded Clinical Evidence of Balneotherapy

Medical water therapy (also called medical hydrology) is practiced worldwide both for relaxation and treatment of diseases. While this practice is still thriving in Bhutan, there is a lack of proper documentation and critical study. Therefore, the current study reports on the water therapies practiced in Bhutan and their health benefits. We used four-stage process: (1) a review of literature on balneotherapy (both traditional textbooks and scientific papers); (2) listing and surveying the hot springs, mineral, and holy spring waters; (3) reviewing the health records of the patients maintained at the traditional hospitals and interviewing traditional physicians and patients about health benefits; and (4) reviewing available literature to identify existing clinical trials data to provide evidence for hydrotherapies. We found three main forms of hydrotherapies are practiced in Bhutan, which comprises herbal bath therapy, balneotherapy, and spiritually empowered waters. The most popular hydrotherapies are herbal bath and hot spring therapies. Herbal bath therapy needs traditional physicians’ prescriptions, while hot springs do not require it. Through field surveys, ten different hot springs (tsha-chu) and 17 medicinal water or mineral springs (sman-chu), and 17 holy spring-waters (sgrub-chu) were identified. In general, medical water therapies are used by the Bhutanese people to treat various ailments, including gastritis, neurological disorders, arthritis, dermatological diseases, and rheumatological and musculoskeletal disorders. Even though a lack of scientific evidence makes it difficult to draw concrete conclusions on their traditionally claimed efficacy and safety, there are clinical evidences documented from other countries.


Introduction
Medical hydrology (MH) (often referred to as medical water therapy or hydrotherapy or hydropathy or water cure) is using water as a therapeutic medium in different physiochemical conditions to prevent and treat health problems [1]. For example, aquatic therapy uses physical exercise in regular water pools for relaxation, fitness, and physical rehabilitation [2]. Spa therapy uses either mineral water or thermal water infused with herbs, stone-heated water, and mud packs for relaxation and therapeutic purposes [3]. While crenotherapy  • Sarpang (Sershong gewog) (332 masl) Except for a few places such as Lhuntse, Mongar, and Bumthang, hot springs (Tsha-chu) and mineral springs (sman-chu) are connected by motor roads in most districts. For example, the farthest hot spring from the motorable road access point was Dur hot spring, which is four days hike from Dur village in Choekhor gewog (gewog-administrative unit) under the Bumthang district.

Study Design, Ethics, and the Data Collection Methods
The current study is a review-guided observational study, described previously [25]. First, we reviewed classical Sowa Rigpa literature including Shelgong shelthreng [26], Four Tantras [13,14], and Khrungpe drimed shelgi melong [27] to generate a background knowledge on hot spring, mineral spring, holy water (sgrub-chu), mantra empowered water (sngags-chu) and herb-infused water called five Amritas herbal bath (bdud-rtsi lnga-lums). The review of literature such as classical text on Bhutan's hot springs and mineral springs [28] allowed us to select and prioritize locations of various hot springs and mineral springs based on their accessibility at the time of our survey. Second, we assessed the current literature on hot springs, mineral springs, and holy springs for recording an updated list of currently known practices in Bhutan. Third, we consulted the traditional physicians (Drung-tsho) and traditional clinicians (sman-pa) using open discussion forums after obtaining informed oral consent from them to authenticate the reviewed ethnomedicinal information. Fourth, several field trips were made to the selected study areas (18 localities under 11 districts) in 2006-2017 for field observations, photographing, sample collections, recording altitude, temperature, and therapeutic properties. We applied the convenience sampling methods to survey thermal, medicinal, and holy waters based on the villagers' oral accounts. The Traditional Medicine Research and Development Committee of Bhutan (TMRDB) reviewed and approved this study, and the administrator (Gup) of respective Gewogs (Blocks), which also arranged porter and ponies were consulted for surveying the research sites.

Field Survey and Identification of Thermal, Medicinal, and Holy Spring Waters
Based on the literature review and other information, the list and the locations of hot springs and mineral spring waters were produced. The altitudes were recorded using a hand-held Garmin Etrex GPS-Altimeter unit (Garmin Ltd., Olathe, KS, USA) and the digital photographs of the different hot springs, mineral springs, and holy springs were taken from the survey sites. Other standard data, including the environment surrounding the waters and locality names, were also recorded at each field site on pre-prepared forms. The identification and validation of therapeutic uses of respective hot spring and mineral spring were conducted by analyzing specific organoleptic properties such as smell, physical appearance, and color of each hot spring at its source as well as the stones around it, its temperature, and finally, the proximity of each subsidiary pool, if applicable. The temperature was recorded with the help of thermometer.

Data Collection on Steam Bath Therapy and Holy Water and Analysis
We formerly interviewed three traditional physicians dealing with herbal bath therapy at National Traditional Medicine Hospital (NTMH) in Thimphu on BSM concept of hydrotherapy. We randomly chose 25 patients availing herbal bath therapy at NTMH and interviewed informally to gain their perceptions about therapy and its benefits. The data on the frequency of patients' visits from the year 2018-2019 were retrieved from patients' daily register logbooks maintained at NTMH, Thimphu. The entire information gathered in this study were analyzed using MS Excel sheet and interpreted into tables and graphs.

Types and Classification of Healing Waters in Bhutan
Based on the oral accounts of the people we interviewed, and the literature data collected in this study, we found that the healing water belong to three main categories: Water 2021, 13, 9 5 of 47 balneotherapies (hot springs and mineral spring water), herbal bath therapy (bdud-rtsi lnga-lums), and spiritually empowered water. Herbal bath therapy is one of the five physiotherapies (las-lnga dpyad-lnga) described in BSM, prepared from five medicinal plants. Hot springs are of two types: natural hot spring (rang-'byung chu-tshan) and artificial hot spring (bcos-ma'i chu-tshan). Natural hot springs are further classified into five types depending upon their mineral constituents: (i) hot spring rich in coal and sodium carbonate (rdo-srol dang cong-zhi 'dres-pa las 'byung-ba), (ii) rich in coal and sulfur (rdo-srol dang mu-zi 'dres-pa las 'byung-ba), (iii) rich in coal and mineral pitch (rdo-srol dang brag-zhun 'dres-pa las 'byung-ba), (iv) rich in coal, sodium carbonate and sulfur (rdo-srolcong-zhi dang mu-zigsum 'dres-pa las 'byung-ba), and (v) rich in coal, sulfur, mineral pitch, and realgar (rdo-srol dang mu-zi brag-zhun ldong-rosbzhi 'dres-pa las 'byung-ba).

Herb-Infused Water (bdud-rtsi lnga-lums) Therapy
The herb-infused water is often referred to as five Amritas or Elixir herbal mixtures bath. It is the fermented products (thang) of mainly five medicinal plants: Juniperus squamata, Rhododendron anthopogon, Ephedra gerardiana, Ajania nubigenum, and Myricaria rosea. This formulation contains an additional 26 minor ingredients. During this study, only Menjong Sorig Pharmaceuticals Corporation Ltd. in Thimphu was found to manufacture the five Amritas as per the BSM formulation and is thus not made by local healers. We found that the traditional physician prescribes the five Amritas formulation for paralysis, rheumatoid arthritis, acid peptic diseases, or bowel movement disorders ( Table 1). The five Amritas is used as the main ingredient in herbal baths, herbal steaming (both localized and general), and herbal compress, which is discussed in the subsequent sections. We found that NTMH at Kawajangsa, Thimphu, currently practices four types of herbal bath therapies, namely, herbal bath immersion (chu-lums) (Figure 2a (Table 1). As per the data we obtained from patients register maintained in the medical record section at National Traditional Medicine Hospital, Thimphu, 4223 patients availed the service in 2019 ( Figure 3).

Steam Bath (rlang-dugs)
In localized herbal steaming therapy, 50 gm of five Amritas extract is mixed and boiled with three liters of water in a pressure cooker ( Figure 2c). Subsequently, once the mixture is ready, the affected body part(s) of a patient is exposed to the pressure cooker's vapor via a sterile outlet for 15 to 20 min (Figure 2d). We observed that temperature is critical in this therapy. The traditional physicians that we interviewed said they never allow the temperature to exceed above 45 °C since, beyond this, it could be disruptive, exceeding the physiological pain threshold, and lose its therapeutic values. The herbal steam bath applied to different points or parts of the patient's body with the heat accompanied by the herbal effect and moisture persuades perspiration, stimulating the skin for better circulation to keep all senses of humor in a harmonious state. The maximum num-

Herbal Bath Immersion (chu-lums)
In herbal bath immersion therapy, we observed that the traditional physicians mix extract from five Amritas (usually five liters of the extract is the recommended volume) with 100 L of hot water, and then the patient remains immersed in the mixture (Figure 2a,b). Patients before immersing themselves in the bath (chu-lums) seek a thorough medical examination from a traditional physician. The bath temperature starts at 37 • C (average body temperature), and then gradually increases to 45 • C. The temperature is again brought down to 37 • C when a patient is about to come out of the bath. In a day, a patient can take a maximum of 30 min for the bathing. We found that an herbal bath is useful for at least 16 different types of ailments ( Table 1). As per the data we obtained from patients register maintained in the medical record section at National Traditional Medicine Hospital, Thimphu, 4223 patients availed the service in 2019 (Figure 3).

Herbal Steam Bath (rlang-lums)
In herbal steam bath therapy, five Amritas herbal mixture is mixed with hot water in a 2:1 ratio (v/v) in a wooden trough, and its steam or hot vapor is used for treating a patient (covered with clean blanket or towel for at least 30 min to get optimal benefits) ( Figure  2e). Both herbal steam bath and localized herbal steaming therapies are known to treat about 10 different diseases ( Table 1). The record maintained by NTMH showed that 10,626 availed herbal steam bath service in the past four years (2016-2019) with increasing trend every year (3777 patients treated in 2019) ( Figure 3).

Herbal Compression (bcing-dugs)
Unlike the other three types of therapies, we found that herbal compression is a straightforward method. Medicinal ingredients are wrapped inside a clean cloth bag or rag and then keep pressing against the patient's affected body parts (Figure 2f). According to traditional physicians in NTMH, the mainstream Sowa Rigpa medical system describes 30 different types of herbal compressions altogether, including 19 hot (tsha-sel) and 11 cold (grang-sel) therapies (often described as purgation therapy in Sowa Rigpa). However, NTMH currently practices only one of those types to treat about 15 different ailments and disorders. We found bcing-dugs is the second most popular herbal bath therapy, and 10,626 patients availed this therapy in the last four years (Figure 3).   Table S1).

Herbal bath immersion
Used for treating gout, arthritis, neurological disorders, stiffness or paralysis of limbs, injury or illness affecting legs or foot, boil or tumor, large ulcer or sore, fresh, and old wounds, stomach ulcer, swellings, hunchback or kyphosis, severe illness, dislocated disc, serous fluid accumulated between flesh and bone, and a sickness of cold character caused by phlegm and wind disorders.

Herbal steam bath
Indicated for post-traumatic pain, swelling of hands and legs, neurological disorder, muscular dystrophy, trembling, obstinate skin diseases, piles, chronic fever, gouts, arthritis, and rheumatism. It also provides relaxation to the stressful mind and body, and depression. It is also indicated for bile or phlegm disorders, and wind disorders.

Steam Bath (rlang-dugs)
In localized herbal steaming therapy, 50 gm of five Amritas extract is mixed and boiled with three liters of water in a pressure cooker ( Figure 2c). Subsequently, once the mixture is ready, the affected body part(s) of a patient is exposed to the pressure cooker's vapor via a sterile outlet for 15 to 20 min (Figure 2d). We observed that temperature is critical in this therapy. The traditional physicians that we interviewed said they never allow the temperature to exceed above 45 • C since, beyond this, it could be disruptive, exceeding the physiological pain threshold, and lose its therapeutic values. The herbal steam bath applied to different points or parts of the patient's body with the heat accompanied by the herbal effect and moisture persuades perspiration, stimulating the skin for better circulation to keep all senses of humor in a harmonious state. The maximum number of patients availed localized herbal steaming among all four herbal bath related services containing five Amritas ingredient during the last four years. It has a similar therapeutic value to the herbal steam bath (Table 1).

Herbal Steam Bath (rlang-lums)
In herbal steam bath therapy, five Amritas herbal mixture is mixed with hot water in a 2:1 ratio (v/v) in a wooden trough, and its steam or hot vapor is used for treating a patient (covered with clean blanket or towel for at least 30 min to get optimal benefits) ( Figure 2e). Both herbal steam bath and localized herbal steaming therapies are known to treat about 10 different diseases ( Table 1). The record maintained by NTMH showed that 10,626 availed herbal steam bath service in the past four years (2016-2019) with increasing trend every year (3777 patients treated in 2019) ( Figure 3).

Herbal Compression (bcing-dugs)
Unlike the other three types of therapies, we found that herbal compression is a straightforward method. Medicinal ingredients are wrapped inside a clean cloth bag or rag and then keep pressing against the patient's affected body parts (Figure 2f). According to traditional physicians in NTMH, the mainstream Sowa Rigpa medical system describes 30 different types of herbal compressions altogether, including 19 hot (tsha-sel) and 11 cold (grang-sel) therapies (often described as purgation therapy in Sowa Rigpa). However, NTMH currently practices only one of those types to treat about 15 different ailments and disorders. We found bcing-dugs is the second most popular herbal bath therapy, and 10,626 patients availed this therapy in the last four years (Figure 3).

Hot Springs (tsha-chus) in Bhutan
The current study found 10 hot springs with a total of 29 natural pools (  Balneologists generally classify hot springs based on temperature, mineral concentration, and pH values. In this study, we recorded the only temperature and classified hot spring based on their temperature ( Table 2). Out of 29 pools from 10 hot spring, only six pools belong to the hot spring category (temperature, >42 • C). While most pools, i.e., 18 pools, belong to warm springs (temperature, 35-42 • C) followed by two pools as tepid spring (temperature, 25-34 • C) and one pool as cold spring (temperature, <25 • C). We found that traditional physicians and classical BSM texts [13,14] classify hot springs into five types based on mineral content. They are hot spring rich in sulfur nativum (mu-zi'i tsha-chu), hot spring rich in sulfur (mu-ljang gi tsha-chu), hot spring rich in lime (rdo-zho'i tsha-chu), water percolating from rocks (rdo-chu'i tsha-chu), and hot spring rich in calcite or carbonate mineral (cong-zhi'i tsha-chu). Additionally, depending upon different minerals in combination, hot springs can also be classified into 101 (chu-tshan brgya-rtsa) different types.
Out of 10 hot springs we surveyed, only two (Gasa hot spring and Gelephu hot spring) were accessible to motor road. The remaining hot springs were located at a few hours hike to as far as three days hike (e.g., Pasalum hot spring in Lhuntse). The most popular hot springs in Bhutan are: Chuboog hot spring in Punakha (    Cures diseases caused by the subterranean spirits called bhupati or lord of earth which are usually associated with festering wounds such as leprosy. Additionally, useful for treating unwanted serous fluid accumulation in joints and lymph in the tissues. Improves facial beauty, alleviates itching disorders, large pustule, and large ulcer or sore.   Note: numbers in brackets indicates the locations in Figure 1 (distribution map). Hot springs are categorized based on their recorded temperature with reference to Pentecost [29] and Pentecost et al. [30]. Gewog: administrative block. masl: meters above sea level. NA: not applicable.
(Central Bhutan), which is the highest amongst all the pools. Chuboog hot spring u Punakha district (Western Bhutan) and Yoenten Kuenjung hot spring under Lhunts trict (North-Eastern Bhutan) had the least water pools with two pools each. Among 1 springs, Chuboog hot spring (in Punakha district) (Figure 4a), Duenmang hot spri Zhemgang district) (Figure 4c), and Gasa hot spring (in Gasa district) (Figure 4e) a three most popular hot springs in the country.

Medicinal or Mineral Springs (sman-chu)
The current study reports 17 mineral springs (Table 3), out of which most visited were those in the Gasa, Paro, Bumthang, and Thimphu districts. For instance, located just half an hour from Thimphu (capital city), the popular mineral spring water, Kabisa mineral spring, has been long used by the people for treating conditions such as migraine, headaches, sinusitis, stomach inflammation (ulcer), backache, fracture, sprain, joint pain, gout, arthritis, abscesses, and skin diseases. The site consists of wooden bathtubs. Many people (patients) camp near the site to ensure access to the mineral springs. We found that traditional physicians and BSM texts [13,14] classify mineral springs into five main types exclusively based on diseases they can cure. These texts suggested that mineral or medicinal springs must contain either sulfur (mu-zi), calcium carbonate (cong-zhi), mineral pitch (brag-zhun), iron oxide/limonite (sindhu-ra), or the mixture of these components ( Table 3). The nature of the taste (specifically, sweet, sour, bitter, hot, and mixed flavors) and the healing properties of each mineral spring varies according to its chemical and mineral constituents. Most of the mineral springs identified in this study possess a rotten egg's characteristic smell. There is a belief among the Bhutanese that the stronger the smell, the better is its medicinal values. Its characteristic rotten egg's smell is linked to the hydrogen sulfide (colorless water-soluble gas). All mineral springs are cooling in nature and are usually associated with reddish brown or yellowish colored water sites/sources ( Figure 5). It is equally popular as hot-spring and has many claimed medicinal benefits (Table 3).

Holy Spring Waters (Sgrub-chu)
There are many holy water sources distributed all over Bhutan. In this study, we have documented only 17 of them and their associated therapeutic properties (Table 4). They are considered the most popular and spiritually significant spring waters. Holy water is a perennial water source, seeping out from underneath the ground or trickling down a cliff. Regardless of the season, the volume or flow of water remains consistent and unchanged. A common folk belief is that holy water emerges from the ground due to the asceticism and blessings of Buddhas and Bodhisattvas. According to the study participants, holy waters are unearthed by some great saints or sages (who are compassionate and may have attained enlightenment) in drought-stricken villages (lack of water supplies) afflicted by the deadly disease, or in places of legendary and sacred temples. Therefore, almost all holy waters reported in the current study are associated with spiritual or sacred sites (gnas). Thus, Bhutanese believe that holy water is very sacred that it can cleanse one's sins (sdig-pa) and defilements (sgrib). Holy water possesses both purging and healing powers.
Some holy waters are associated with many spiritual as well as medicinal benefits. For instance, the Tsheringma holy water of Tshangkha village in Trongsa district ( Figure 6) is believed to have been established by the deity of longevity (goddess-tshe-ring-ma) and thus, drinking or bathing in it is believed to enhance one's longevity. This holy water is sought to treat throat-related disorders, and the Bhutanese believe that this spring water can progress melodious voice, a quality usually desired by singers. Some study participants said that people from Tshangkha village who live nearby the Tsheringma holy water have a particularly melodious voice since it is their primary source of drinking water. The Dobdrek holy water of Dobji Dzong was unearthed by a Tibetan Saint, Jetsun Milarepa (1040-1123), and residents nearby believe that its origin is Druk Ralung in the Western Tibetan region of China. In addition to cleansing sins and defilements, nearby communities firmly believe that this holy water heals stomach inflammation, headache, wounds, tumor, warts, and blood pressure. It is also used as tonic water. Another healing water of Bartsham in the east (under Trashigang district), but one not necessarily holy water, is Jomorichu, said to have been established and blessed by Ama Jomo (deity of a lake, which is also considered nor-lha). The people of Bartsham and Biddung villages use it against tumors, headaches, and general ailments.

Blessed Rainwater (khrus-'bab chu)
The blessed rainwater in the Bhutanese context (khrus-to bath or purify or cleanse; 'bab-descent; chu-water) means cleansing one's body with the blessed waters [31]. We found that Bhutanese celebrate the blessed rainy day (popularly known as khrus-'bab dus-chen) at the end of every monsoon season, mainly in Eastern Bhutan. According to Bhutanese astrologers (gzhung-rtsi slob-dpon), the Sun enters Virgo (one of 12 zodiac constellations) and transits this area on average between August 23 and September 22. It coincides with the eighth Bhutanese month, and for a week, during which sun directly shines on the star Rishi (sage or drang-srong in Bhutanese language), which is Canopus (second brightest star seen from the earth). Astrologers believe that star Rishi is a medicinal star formed out of crystal (chu-shel) and gemstone (ke-ta-ka), which has the power to purify water. When the sun directly strikes the crystal and gemstone of the star Rishi, the rays emitting from the star reach the water bodies on earth and subsequently known to purify by disinfecting any pathogen and toxicity present in them. Thus, BSM medical system recommends using the water to treat diseases and enhance health and vitality during this week. An astrologer predicts the specific time of the week, and people put containers filled with water outside for overnight on that predicted day to receive the light of the Rishi star. Bhutanese use this blessed water for either drinking or bathing. People also bath in open streams and ponds during this event.

Spiritually Empowered Waters
We identified three types of spiritually empowered waters. They are mantra-empowered water (sngags-chu), ablution water or sacred cleansing water (khrus-gsol-chu), and ambrosia from the vase (bdud-rtsi bum-chu). There was no literature describing the precise quantity and variety of ingredients added into each type of waters as it depends upon the recipe for the ritual's specific tantric tradition and purposes. In Bhutan, the spiritual master (bla-ma) recommends mantra-empowered water patients afflicted by an evil spirit (gdon). The mantra-empowered water is made from regular drinking water, blessed with spiritual mantra power through visualization and chanting of prayers and mantras. The sacred cleansing water may or may not contain herbs, but saints or Buddhist master spiritually empower it by reciting the relevant mantras. This spiritually empowered water is usually poured over the patient (beginning from the head part) to heal the ailments associated with contamination or defilements, impurities (ma-dag-pa), and negativities (gnas-ngan).
Traditional physicians in the interview said that ambrosia from the vase contains water, Cinnamomum camphora (ga-bur) and Crocus sativus (dri-bzang) and stored inside a container or vase (bum-pa). People also take this water (bdud-rtsi bum-chu) during religious ceremonies such as sgrub-chen (sgrub-chen-great accomplishment practice or rite of high attainment for seven days), tshe-gcu (annual rituals performed by the public to bring in timely rain, bumper harvest, peace, prosperity, and sound health for the families and communities) and other related ceremonies. All temples, monastery, and home shrine have sacred cleansing waters (khrus-chu and bdud-rtsi bum-chu), and they sprinkle sacred water (bdud-rtsi bum-chu) every time they make an offering to appease deities. Anyone, including foreign tourists visiting the temple or monastery, experience sacred water or ambrosia from the vase (khrus-chu or bdud-rtsi bum-chu).

Meta-Analysis of the Literature on the Clinical Studies of Balneotherapies
We initially identified 135 potentially relevant articles, and out of it, 113 articles were excluded, including review articles and those that are not clinical studies. Finally, 22 randomized clinical trials (RCTs) regarding balneotherapy in various medical fields between 2012-2019 were analyzed ( Table 5). The majority of RCTs were on the use of balneotherapy in osteoarthritis (six out of 22 RCTs-27.3%), and improvement of mental and quality of life (six out of 22 RCTs-27.3%), followed by three RCTs in rheumatological and other musculoskeletal diseases, two each in fibromyalgia and psoriasis, one each in mastalgia and terminal stage cancer. Three trials were specific to knee osteoarthritis. These 22 RCTs evaluated a total of 1648 patients. Out of 22 RCTs, eight were from Italy and Hungary (four each), three from Turkey, two from Japan, Germany, Lithuania, and one from China, Thailand, France, Iceland, and the Republic Korea each. Balneotherapy yielded better or significant clinical improvements in patients (21 out of 22 RCTs) than their control groups. Although each RCT uses slightly different indices, measurement of the reduction in pain severity using the visual analogue scale (VAS) was the most common outcome examined in 12 out of 22 RCTs.
Balneotherapy not only improved clinical outcomes, but some of the RCTs did result in the reduction of the use of pharmacological drugs such as non-steroidal anti-inflammatory drugs (NSAIDs). A meta-analysis of 29 RCTs on the therapeutic effect of balneotherapy by Falagas et al. [32] indicated statistically significant pain improvement in patients with rheumatological and other musculoskeletal diseases. In another study on Chinese herbal bath therapy, the herbal bath is recommended as a complementary therapy to improve the pruritic symptoms in uremia patients [33]. Although, in almost all RCTs, balneotherapy significantly improved clinical outcomes in patients with various diseases, yet available literature is still inadequate to draw a concrete conclusion, including their biological mechanism of action.   61.5% of patients showed significant reduction in cortisol level between pre-and post-moor bath in week 1 (p < 0.008); and in 46.2% of participants between preand post-moor bath in week 3 was non-significant (p< 0.1617). Blood pressure was after moor bath. Heart rate increased during moor bath but was significantly lower in week 3 compared to week 1. Mood state significant improved after both moor baths.
[38] Mental and physical state were examined using two sets of self-designed questionnaires in the health examination center.
Sleep disorder (difficulty in falling asleep (p = 0.017); dreaminess, nightmare suffering, and restless sleep (p = 0.013); easy awakening (p = 0.003) and difficulty in falling into sleep again after awakening (p = 0.016); and mental stress (p = 0.031) and problems of general health (head pain (p = 0.026), joint pain (p = 0.009), leg or foot cramps (p = 0.001), blurred vision (p = 0.009)) were relieved significantly in Group I compared to control (Group II). Relief of insomnia, fatigue, and leg or foot cramps was greater in old-age group than in young age-age group (p < 0.05). Waist circumference was significantly in women below age of 55 years (p < 0.05) but not in men.
[39]     At week 2, VAS in the balneotherapy (BT) group, was significant (p < 0.0001) reduced and persisted at 3-and 6-month follow-up. VAS was non-significant in control group. FIQ total score in the BT group improved significantly after 2 weeks (p < 0.001) and persisted significantly until 6 months (p < 0.0001). significant reduction in WPI in BT group after week 2 and persisted until 6 months-p < 0.0001. in control group-p < 0.05. SS score in BT group-p < 0.05-0.0001 until 6 months. Significant improvement of SF-12 MCS and CES-D in BT group-p < 0.01 and persisted until 6 months follow-up (p < 0.0001 and p < 0.05 respectively).
[45] Group I (treatment group) showed significant improvement in all scores compared to control group II: VAS in Group at 3 w and 3 months both significant-p < 0.001 and p < 0.008 respectively. Group II showed reduced pain only at 3 w-p < 0.006. WOMAC score in Group I was significant at both 3W and 3 months: activity-p < 0.001, stiffness-p = 0.004, pain-p = 0.002 (at 3 w); activity-p < 0.001 (at 3 months). SF-36-significant improvement in vigorous activities in Group I (p = 0.005).
[46] MDA, NSSA, AOP, and SOD were determined at baseline and after the treatment (2 w).

References
Chronic low back pain.
Group I (n = 52): thermal mineral water treatment plus usual musculoskeletal pain killer treatment. Group II (n = 53): traditional musculoskeletal pain killer treatment alone.
Severity of pain using VAS score, functional disability using the Oswestry Disability Index (ODI), and the quality of life using the EuroQol Five Dimensions Questionnaire (EQ-5D) were determined before, right after, and 9 weeks after 3 weeks therapy.
VAS score of existing low back pain at rest decreased significantly in Group I (p <0.001) after 3 weeks balneotherapy and persisted in the follow-up period. ODI improved significantly in Group I (p < 0.001); EuroQol-5D index on QoL improved significantly (p < 0.001); EuroQoL-VAS showed improvement in the current state of health (p < 0.001).

Number of patients requiring
NSAIDs, opioids, muscle relaxants, and paracetamol for low back pain decreased after balneotherapy treatment.
Severity of pain using VAS score, clinical knee evaluation using range of motion (ROM) and lower limb muscle strength, Italian validated versions of WOMAC and Lequesne Algofunctional Index were determined at baseline, after 8 weeks and 6 months after 8 weeks treatment.
At week 8: VAS score for pain reduced significantly in Group I (p = 0.0039) during walking in flat surface. At month 6: VAS core persisted significantly low (p = 0.00954).
WOMAC score reduced significantly between baseline and week 8 (p = 0.0137), between baseline and 6 months (p = 0.006438). No significant improvement in kinetic path assessment.
Group II (n = 21): mud-bath treatment alone. Both groups received their respective treatment once daily for 6 days/week for 2 weeks. Mud was applied at a temperature of 47 • C for 10 min, and thermal immersion (38 • C) for 10 min daily. Assessment: baseline, 2 w, 12 w follow-up. TM: patients allowed to continue their usual pharmacological treatment. Multidisciplinary approach study. 41 patients (31-69 years age group).
Pain severity using VAS, Fibromyalgia Impact Questionnaire (FIQ), and SF-36 questionnaire for evaluation of QoL were measured at baseline, after treatment (week 2), and week 12 post-treatment.
Group II showed better outcome: Pain (VAS)-p < 0.05; FIQ-p < 0.05; SF-36 PR physical role-p < 0.05. Group I showed significant improvement in only pain VAS-p < 0.05. Rest were non-significant compared to group that received mud-bath alone.
[51] Severity and extent of psoriasis were measured by the Psoriasis Area and Severity Index (PASI) highly sensitive C-reactive protein (CRP) was measured from venous blood samples before treatment and discharge.
Both PASI score and CRP levels showed improvement of psoriasis after balneotherapy-based rehabilitation. Methotrexate receiving patients had significantly lower PASI scores both on admission (p = 0.015) and before discharge (p = 0.031).

Worldwide Practices of MH Accentuating Bhutanese Perspectives
Hydrotherapy is practiced worldwide, such as North and South America, Europe, and Asia (Thailand, Japan, Indonesia, and China) [33]. For instance, the Japanese use three main types of hydrotherapy, namely, onsen (hot spring bath), furo (bathing in a tub), and sento (public bathing), particularly onsen or Touji therapy is said to have practiced from as early as 700 B.C. [56]. Chinese herbal therapy containing 11 herbal ingredients [33] is used effectively against itching resulting from uremia [57]. In Bhutan, the MH is still very popular among the Bhutanese to maintain their health and treat illnesses. Moreover, herbal bath therapy (bdud-rtsi lnga-lums) is incorporated as one of the alternative treatment regimens in the mainstream BSM to treat pain, rheumatism, respiratory diseases, skin diseases, osteoarthritis, and uremic pruritus. Ladakhi Amchi (traditional physician) in India practices herbal bath therapy (bdud-rtsi lnga-lums), which is similar to that of the Bhutanese herbal therapy with slight variations in the decoction formulations [58]. This herbal bath therapy (known as 'lums medicinal bathing' in Tibetan) is also used (with slight variations in the formulations) in Tibetan medicine, and the Chinese government has recently registered this lums medicinal bathing as one of the UNESCO's Intangible Cultural Heritage in 2018 [59]. Lums medicinal bathing is very similar to the bathing culture practiced in indigenous medicine systems of India, Egypt, Europe, Russia [60], and Bhutan. Indeed, the scholarly Tibetan medicine is believed to be the hybrid of other major scholarly medicine systems such as Ayurvedic, Greco-Arabic, and Chinese traditional medicines [61]. Thus, origin, practice, development, transmission, and ownership (as cultural and knowledge property) for indigenous medical practices, including lums medicinal bathing, are very complex and controversial. Except for slight variations in the techniques and recipes used, the purpose, beliefs, and history of MH practiced worldwide are almost similar.
Balneotherapy or mineral water-based therapy is also practiced worldwide [12]. Japan has the highest number of hot springs (27,000 sources in 3170 locations) in the world, and according to their law (Hot Spring Law-1948), therapeutic hot spring must have a temperature not less than 25 • C and should contain at least one out of 19 mineral components [62]. Japanese categorizes hot springs based on three parameters, namely, chemical content (consist of nine types), water temperature (consist of four types), and concentration of hydrogen ions (consist of five types) [62]. In Taiwanese culture, hot springs are of three types: sulfur-rich acidic hot spring, hydrogen carbonate-rich neutral hot spring, and chlorine-rich acidic hot spring [63]. In Bhutan, almost all hot springs are said to be rich in minerals. According to few MH traditional documents, including "Hot springs and mineral springs of Bhutan" [64], a classical text on Bhutan's hot springs and mineral springs [28], and Khempajong hot spring (mkhen-pa-ljong gnyes tsha-chu) [65], hot springs in Bhutan are rich in coal (rdo-sol with various colors ranging from light blue, blue-black, and whitish), sulfur (mu-zi or mu-ljang), limestone (rdo-thal), mineral pitch (brag-zhun), and sodium carbonate (cong-zhi). However, there are no scientific geochemical studies conducted so far to quantify their mineral contents. The current study could classify hot springs based on only water temperature as hot-, warm-, tepid, and regular cold springs. There is an urgent need for more rigorous scientific studies on Bhutanese hot springs and mineral springs to characterize mineral compositions present in each hot spring pool.
Bathing in the hot springs and mineral springs facilitates direct adsorption of minerals, such as calcium, chlorine, fluorine, iron, magnesium, potassium, silicon dioxide, sodium, and sulfur through the skin, which in turn can treat skin conditions such as atopic dermatitis and psoriasis [66][67][68]. Sulfurous mineral waters have been long used in the MH for treating numerous diseases, and recent studies and clinical trials are showing benefits of topical application of sulfurous mineral waters and sulfurous muds (peloids) for hand and knee osteoarthritis, rheumatoid arthritis, skin diseases, chronic inflammatory diseases, and alleviating anxiety in the patients with chronic diseases such as terminal stage cancer [36,47,52,53]. The beneficial effect of such waters and muds (peliods) is mainly due to the presence of sulfur in the form of hydrogen sulfide (H 2 S), which is formed naturally from organic decomposition. Sulfur compounds in the water are said to break the mucin's disulfide bonds and activate breathing and blood circulation and reduce inflammation [69]. Our body can endogenously produce small quantities of H 2 S, which act as a neuromodulator in the brain, and within the vasculature promotes vasodilation and growth of new vessel [70]. Moreover, H 2 S is described as gasotransmitter, which functions as a signalling molecule involved in the cytoprotective functions [71]. However, exposure to H 2 S at certain concentrations can be toxic equivalent to carbon dioxide and cyanide and thus it is crucial to determine the chronicity of sulfur concentrations and to define the treatment duration in the sulfurous hot springs and mineral waters.
The spiritually empowered water therapy or holy water is also prevalent in many countries, and this is captured comprehensively by the book on "Spiritual Bathing: Healing Rituals and Traditions from Around the World" [72]. Holy water or blessed water plays a central role in different religions such as Christianity, Hinduism, and Buddhism [73]. The cultural traditions may slightly differ, but their beliefs are almost similar. In Christianity, water sprinkling onto a person's forehead or immersing in the water (baptism) symbolizes purification, regeneration, and admission to the Christian Church [74]. In Hinduism, the river Ganges is considered as a goddess and divinely, and the devotees drink and undertake purification bath, as well as it is customary for the Hindus and Sikhs to scatter the ashes of the cremated bodies into the river to transport their soul to the next life [73]. In the Shintoism culture (modern sect Shinto) of Japan, the use of water in purification rituals is still prominent today [75]. In Buddhism, primarily practiced in Bhutan, at least three types of holy waters, namely, mantra-empowered or blessed water (sngags-chu), ablution water or sacred cleansing water (khrus-gsol-chu), and ambrosia from the vase (bdud-rtsi bum-chu) are distinguishable. Unlike the other two forms of spiritually empowered waters, ambrosia from the vase uses medicinal herbs, including Cinnamomum camphora and Crocus sativus. It is interesting to note here that camphor present in C. camphora possesses antiseptic, analgesic, antipruritic, counterirritant, and rubefacient properties, and the whole plant infusion is used as an inhalant treatment for cold and lung diseases [76]. C. sativus contain more than 150 compounds, including crocin, which renders yellowish-orange color to the water (bdud-rtsi bum-chu) [77]. Interestingly, yellow-orange color is linked to the color of the robes worn by spiritual masters.
Amongst three water-based therapies of Bhutan, herbal bath and balneotherapy are the most popular practices in Bhutan. These therapies heal the patients from chronic diseases and give other users an increasingly adjusted and incorporated life, helping them rejuvenate their worn-out body, restoring the psyche, and empowering the soul. The government's recent move to make them the centerpieces of eco-and health tourism, to a greater extent, embodies an idea that consolidates medical treatments, well-being, recreation, unwinding industry, and cultural excellence. While these two forms of waterbased treatments have commercial applications, there is a need to evaluate the quality and safety of herbal bath and balneotherapy in Bhutan.

Herbal Bath Therapy
Herbal bath therapy is an integral part of traditional BSM health care services. We have previously described how QSE of BSM is managed and regulated under the settings of university medical education, hospital services, and pharmaceutical production processes [78]. We found that NTMH developed numerous standard guidelines and reference materials through a series of consultative workshops to provide BSM treatments with the same quality, safety, and effectiveness. These guidelines are (i) diseases codes and classification system for correctly diagnosing the diseases; (ii) standard treatment guidelines for traditional medicine; (iii) national traditional medicine professional service standards; (iv) therapy guidelines (including herbal bath therapy) for traditional medicine practitioners; (v) standard operating procedures for traditional medicine services; and (vi) guidelines for detecting, reporting, and managing adverse drug reactions [78][79][80][81]. The traditional physicians and clinical assistants are trained on following, operating, and using these guidelines while providing the traditional medical health care services. In a study conducted by Wangdi [82] on the efficacy of herbal bath therapy in Bhutan, 163 out of 226 patients (72%) interviewed showed a positive response, and only 22 patients (10%) experienced discomfort such as headache and nausea during the treatment. It is likely for this reason that herbal bath therapy is the most popular treatment availed by patients visiting NTMH in Bhutan.

Balneotherapy and Clinical Trials
Balneotherapy has been used worldwide for more than thousands of years, and it is still arguable as this practice would not have lasted that long if it were not effective. However, a long history of traditional uses cannot be taken per se as scientific proof of efficacy unless proven from a mechanistic point of view. Maintaining hygiene is critical in balneotherapy. Because thermal waters are rich in microbial organisms (both natural and introduced) [83][84][85], including infectious Clostridium [86] and Legionella strains [87], and cyanobacterial toxins [88], the waters can be hazardous for users [89,90] if they are not appropriately managed. Cyanotoxins, such as microcystin-LR produced by an alga (Microcystis aeruginosa), which is common worldwide in drinking water reservoirs [91], is hepatoxic [92] and can cause death [93]. Mohamed [88] detected toxic cyanobacteria and cyanotoxins in the public hot springs in Saudi Arabia. It is most likely that Bhutanese hot springs may contain such toxic microbes as their water sources are freshwater and have similar physiochemical properties, including the water temperature. Contamination of hot spring by legionellae (Legionella pneumophila) is also common and was isolated from many hot springs in Japan [94], which causes Legionnaires' disease [95,96]. Such risks associated with the use of hot spring waters have led to the revision of Japanese Onsen Law in 2007 and incorporated compulsory testing for Legionella contamination every year and analysis of onsen water at source or entry to the bathtub every five years [62]. In addition to infectious and toxic microbes, hot springs also contain a considerable amount of heavy metals [97], which, if exposed to long-duration, may be adverse to human health.
Traditionally, the QSE of hot springs and mineral spring water is driven by faith and is often more inclined to adhere to strong cultural and spiritual beliefs [65]. For example, in Bhutan, appeasing the guardian deities of the hot spring and mineral spring water sites and maintaining absolute cleanliness of the water sources and pools, and their surrounding areas are the most customary practices among visitors. Before visiting hot or mineral spring sites, visitors consult an astrologer or traditional physician to determine the appropriate time of the visit and obtain specific instructions for deriving the best therapeutic benefits. Generally, the Bhutanese consider the period between the 16th-30th days of the tenth and eleventh months-in winter or of the second and third lunar months in spring Bhutanese lunar calendar year (mar-ngo tshe) as the best time to visit hot springs. They believe that there are least disturbances by other cosmo-physical elements during these periods and that the health is progressive, and the hot or mineral spring waters are empowered to yield the most effective result. Women and girls who are on their menstrual periods refrain from entering the hot spring pools. It is believed that any unhygienic activities would provoke the wrathful guardian deities, whose punishments range from sudden snowfall, downpours of rain accompanied by abnormally large hailstones, dreadful lightning, and thunder. We have previously described in detail the cultural and religious beliefs associated with balneotherapy practices elsewhere [65]. Such belief systems have shaped and helped maintain Bhutan's hot or mineral spring water sites serine and clean.
There are limited studies on the quality, safety, and efficacy of the Bhutanese hot springs and mineral spring waters. However, our literature review and the meta-analysis of the published information on balneotherapy shows that about 22 randomized clinical trials have been conducted between 2012-2019 (as shown in Table 5). The majority of the randomized clinical trials focused on osteoarthritis and general improvement of quality of life, and most of these trials were reported from Italy and Hungary. Although, bal-neotherapy yielded better or significant clinical improvements in patients especially with osteoarthritis compared to control groups, their mechanism of action remains unknown. Since hot springs and mineral spring water therapies are popular in Bhutan, there is urgent need for conducting clinical trials, as well as assess their adverse health implications.

Spiritually Empowered Holy Waters
Drinking spiritually-empowered holy water is common in Bhutan and other parts of the world, including Europe [98] and Japan [62], because they believe it contains curative power. A study conducted by Kirschner et al. [99] found that holy water could be underestimated sources of illness since holy water kept in hospital chapels and frequently visited churches contained pathogens such as Pseudomonas aeruginosa and Staphylococcus aureus. In Bhutan, mantra empowered water (ngag-chu), sacred cleansing water (khrue-selchu) and herb-infused holy water (bdud-rtsi bum-chu) kept in the temples are commonly used for treating patients suffering from defilements and afflictions caused by evil spirits. Mantra empowerment is conducted by lay priests (Gomchens) or astrologers (rtsip) or Buddhist spiritual masters (bla-mas or Rinpoches) by reciting the specific mantra and blowing or whooshing the fresh tap water inside the containers. While there is no risk associated with the spiritually empowered waters, their long-term storage may likely facilitate the growth of pathogens that may cause infections in those who seek blessing via drinking or wetting their head with holy waters. It is also possible that during the act of empowerment, whooshing may produce saliva droplets that could potentially spread microbial infectious diseases (e.g., SARS-CoV-2 and tuberculosis) if a person who is conducting water empowerment has the infection.

Conclusions and Future Directions
Medical hydrology or hydrotherapy in Bhutan still holds a firm position as an alternative healing option, for the country is rich in herbal and mineral water resources with curative and therapeutic benefits. Out of three types of MH practiced in Bhutan, herbal bath and balneotherapy have greater potential for applications in health care and eco-health tourism. This study identified four types of herbal bath therapies, ten hot springs, 17 mineral springs, and 17 holy spring-waters in Bhutan. While the traditional physicians prescribe herbal bath therapies, and the treatments are done within the hospital or health care facilities, balneotherapy is an open-access resource commonly used by the people without consultation. Although herbal bath and balneotherapy are both claimed to be effective against chronic diseases such as arthritis, rheumatism, musculoskeletal and neurological disorders, urinary tract infection, and dermatological diseases; their efficacy remains anecdotal without proper documentation of the clinical data. Therapeutic claims of all forms of MH need to be substantiated through clinical studies, and we believe that it can be done using appropriate methodologies described by other international researchers, whose works we have discussed earlier in this study. Collecting scientific or clinical works on balneotherapy that has already been carried out by international researchers and societies would improve the education level and overall knowledge of the traditional Bhutanese physicians. This would help foster better collaborations between researchers in Bhutan and abroad. Such collaborations would improve the quality and trigger number of clinical trials and the medical standards of MH in Bhutan. Future works are required in the following areas:

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Conducting randomized clinical studies on four herbal bath therapies currently offered by the NTMH, Thimphu.

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Determining the pH, microbiological composition, and chemical compositions of all hot springs and mineral springs and develop a comprehensive monograph for geothermal resources in the country.

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Conducting correlational studies between their chemical compositions and traditionally claimed health benefits.
• Formulating an appropriate law and regulations, including compulsory water quality testing of hot springs and mineral springs.