## 4 Discussion  
The aim of this study was to determine whether a series of five carboxytherapy sessions affects the hydration and viscoelasticity of the skin around the eyes (Figure 2). This topic was undertaken in response to reports suggesting that carboxytherapy may also improve other functional parameters of the skin, such as hydration and epidermal thickness, including the improvement of skin hydration [7; 8; 9]. Interestingly, recent research by [PERSON] et al. found that carboxytherapy significantly increases epidermal thickness. Histological evaluation and histometric analysis conducted prior to striae distensae treatment revealed a thin and flattened epidermis with attenuated rate ridges in most skin biopsies. Following treatment, there was a noticeable morphological and architectural improvement in the epidermis, including the development of rete ridges (marked undulations of the dermoepidermal junction) [6]. While our study did not directly measure epidermal thickness, the observed improvements in hydration and viscoelasticity, as indicated by Corneometric and Cutometric assessments, suggest an indirect enhancement of epidermal structure. These findings align with trends reported in previous research, where functional improvements often correspond to structural changes. For instance, a study evaluating a carboxytherapy gel mask demonstrated significant improvement in skin quality, including hydration and reduced erythema, dryness, and crusting, following a nanofractional radiofrequency treatment. Although this method does not involve injectable carboxytherapy, its ability to accelerate wound healing and improve epidermal structure supports the potential multifaceted benefits of carbon dioxide treatments in skin rejuvenation [12; 13]. For instance, a clinical study by [PERSON] et al. demonstrated that the transcutaneous application of a CO2 gel led to significant improvements in microcirculation, including an increase in vertical and horizontal capillary density and a reduction in areas of ischemia. These dermal changes were found to be comparable to those achieved with subcutaneous CO2 injections. These results further support the potential of carboxytherapy, both topical and injectable, in  
Figure 2: Patient (**A**): woman, 32 years old—carboxotherapy combined with lactobionic acid; patient (**B**): woman, 44 years old—carboxotherapy combined with ferulic and ascorbic acid; patient (**C**): woman, 37 years old—carboxotherapy combined with lactobionic acid. enhancing the structural and functional properties of the skin. Improvements in tissue oxygenation, microcirculation, and vascular density underline the multifaceted benefits of CO\({}_{2}\)-based therapies in promoting skin rejuvenation and repair [14]. In the present study, the evaluation of skin hydration using the Corneometer did not yield statistically significant results for either the right side (\(p\) = 0.101) or the left side (\(p\) = 0.052). However, a general trend of improved hydration was observed, with 59% of participants in the carboxytherapy group and 74.4% in the combined treatment group showing improvement. The overall mean increase in hydration across the study group was 2.47 units. Notably, the obtained results can be explained by the fact that only 8 out of 39 individuals in our study had dry skin in the area of the eyes (Cromeometer readings below 60) before the start of the treatment series. In the case of these patients, the increase in skin hydration amounted to 9.351 units (mean value). In our opinion, the impact of applied therapies would be more significant if more people with dry skin were enrolled in this study. Our results of the R6 parameter measurements using the Cutometer indicate that carboxytherapy significantly enhances skin viscoelasticity, as evidenced by statistically significant outcomes for both the right (<0.0001) and left (<0.0001) sides of the face.