## 4 Discussion
After the 19 th treatment, however, SG skin had higher values of hydration of the stratum corneum than before the treatment series, with no differences noted in CG. An improvement in hydration was observed after the first treatment on forearm skin in CG, and the noted increase reached statistical significance. An improvement in hydration was also indicated in an earlier study [13], but statistical significance was not achieved. In that study [13], the skin of the volunteers was in the range corresponding to dry, while in the present study, the skin of the volunteers was determined to be properly moisturized, which may affect the final outcome of the study and suggest that for dry skin, the cryogenic stimulus alone will not be sufficient. The only adverse change noted in both groups during the treatment series was increased TEWL, which may be due to an increased vascular reflex in response to cold. [PERSON] et al. [13] also reported an increase in TEWL after a single WBC treatment. SG was initially characterized by higher TEWL values than CG, which is consistent with previous observations [36; 37]. [PERSON] et. et al. [38] reported significantly lower TEWL values in obese subjects compared to the normal-weight group, but no correlation between TEWL and BMI was indicated. In the present study, such a correlation was noted, as was [PERSON] et al. [22]. The authors noted that as BMI increased by 1 km/m\({}^{2}\), TEWL increased (0.221%). Obese patients have larger skin folds and thicker layers of subcutaneous fat. For proper thermoregulation, this group, compared to normal fat subjects, will sweat more, hence water evaporation from the skin surface will be higher [39]. The normal pH of the skin is in the range of 4.1-4.8, which ensures the integrity and integrity of the stratum corneum and the regulation of epidermal barrier homeostasis [40]. Acidic skin pH also protects the commensal skin microflora, which acts as the first line of defense against pathogens [41]. As a result of a number of factors (e.g., diabetes, skin aging, and skin diseases), microbial dysbiosis can occur, increasing the risk of infection [42]. [PERSON] et al. [36] did not indicate changes in the skin microbiota among individuals with varying degrees of body fatness. The present study did not indicate differences in baseline pH measurements between the groups, which is consistent with the results of [PERSON] et al. [43], who also showed no differences in pH measurements in subjects with normal and high BMI. However, the study by [PERSON] et al. [44] indicated that skin pH was slightly higher in the group with higher BMI. Initially, the pH in the SG increased significantly, reaching values on the borderline of physiological skin pH, with a subsequent significant decrease. CG reacted inversely to the treatments, but pH values were within the range of physiological values throughout. In other work on cryotherapy [24; 45], the pH values also remained in a constant acidic environment, but in contrast, no significant differences were noted during the treatment series. Therefore, it can be concluded that cryotherapy does not negatively affect the pH of the skin, and thus it can be assumed that it does not have a negative effect on the skin's microbiome and hydrolipid barrier controlled by its well-being. However, confirmation of this hypothesis requires further research. Measurement of pH is assessed by the presence of water present on the skin surface. The highest pH values were indicated in the most hydrated areas [46]. Increased TEWL would therefore indicate higher pH values. It is worth noting that an inverse relationship was noted in the study participants. As TEWL increased, pH values decreased, and vice versa. Both characteristics are key indicators of proper hydrolipid barrier function. It is possible that the skin, in response to increased water loss, triggers defensive reactions to maintain the integrity of the epidermal barrier, thus decreasing the pH value.