# Unveiling the Role of Minerals and Trace Elements of Thermal Waters in Skin Health
## 2 Minerals, Trace Elements, and Other Compounds of TSW in Skin Health
### Anions
#### 2.1.1 Chloride  
The chloride anion, along with the sodium cation, is essential for the water balance of tissues. Furthermore, it has been shown that the osmotic forces of water with sodium chloride play an important role in the loss of transepidermal water, favoring the skin's renewal capacity and the recovery of its barrier function [63]. The anti-inflammatory potential of sodium chloride waters has been demonstrated in different studies. [PERSON] et al. [10] studied the effects of bathing in Leopoldine water (salso-sulfate thermal water) in psoriatic patients, showing a decrease in PASI after 4 weeks of treatment. Further, in vivo studies showed the anti-inflammatory effects of Leopoldine mineral water on human skin affected by modest inflammatory reactions caused by the direct application of the chemical irritant sodium lauryl sulfate (SLS) [11]. Hae-Un-Dae TSW sodium chloride, sulfate-rich spring water showed immunomodulatory effects. A murine model of imiquimod-induced psoriasis-like skin inflammation was used to test HUDTSW compared to distilled water (DW); mice were bathed in HUDTSW for 5 min a day for 2 weeks, and the severity of skin erythema and scales were evaluated, and serum levels of inflammatory cytokines were measured. The results showed that the HUDTSW group had faster improvement in terms of skin erythema and scales than the DW bathing group. A substantial reduction was observed in the lesional mRNA levels of IL-17A and IL-23 in the mineral water group. Serum levels of IL-4 and IL-5 were significantly decreased in the HUDTSW group but not in the DW group, and normalized T-cell proportions were observed after bathing [12]. A clinical study compared bathing in hypersaline mineral water (chloride: 152,140 mg/L, sodium: 102,630 mg/L) (A group) with 311 nm UVB phototherapy (B group) and a combination of both mineral water and phototherapy (C group) in patients with stable psoriasis vulgaris of more than 1 year's duration and a PASI score of more than 10. After a regimen of 3 weeks with 5 days of treatment a week, the results showed that groups B and C were similar (reduction in PASI of \(-\)64% and \(-\)55%, respectively), and for group A, the change in PASI was \(-\)29%, indicating less efficacy than in groups B and C [13]. In any case, the treatment of psoriasis with hypersaline water has proven to be an effective alternative for patients in whom phototherapy is contraindicated. An in vitro study compared standardized water and highly mineralized natural mineral spring water (HMW) of a chloride-sodium-sulfate type to test the effects on atopic dermatitis-like inflammation in hairless mice. The results showed that the 100% pure(PHMW) and 10% diluted (DHMW) HMW significantly decreased the scratching behavior; the serum IgE level was also significantly decreased in the DHMW group as compared to the control group. Additionally, the level of inflammatory cytokines in the serum, such as interleukin (IL)-1B, IL-13, and tumor necrosis factor-\(\alpha\), were significantly inhibited in the PHMW and DHMW groups. Furthermore, the total serum reactive oxygen species (ROS) level was significantly decreased in the PHMW group, and the serum malondialdehydedehyde level in the PHMW group was lower than in the control group [14]. As HMW contains other ions and trace elements (Ca, Mg, Sr, and Mn), the effects cannot be attributed solely to the presence of the major ions; the minor ones and trace elements must also be considered. Recently, a combination of La Solia TSW (chloride-sodium-sulfate-type, rich in calcium and magnesium), and a diatom extract (species found in the sources of this spring water) demonstrated anti-inflammatory properties. The mixture was assessed during pro-inflammatory stimulation in an in vitro system mimicking keratinocytes under skin irritation. The mentioned ingredient effectively attenuated the induced levels of different pro-inflammatory mediators (IL-6, IL-1, TNF\(\alpha\), NF-\(\kappa\)B, and CCL1) at the level of gene expression.