###### Abstract  
Carboxytherapy is a promising treatment modality with multidirectional effects on the skin; yet, its impact on hydration and viscoelasticity in the delicate periorbital area requires further exploration. This study aimed to evaluate the effects of carboxytherapy as monotherapy and in combination with selected acids on the hydration and viscoelasticity of the skin around the eyes. Thirty-nine participants underwent five weekly treatments, with carboxytherapy applied to the right eye area and carboxytherapy combined with acids (ferulic acid 14% with L-ascorbic acid 12% or lactobionic acid 20%) administered to the left eye area. Skin hydration and viscoelasticity were measured using Corneometer and Cutometer probes, respectively. Statistically significant improvements (\(p<0.0001\)) in viscoelasticity were observed in both treated areas. The combination of carboxytherapy with lactobionic acid led to a modest but statistically insignificant increase in skin hydration. These findings indicate that carboxytherapy, particularly in combination with tested acids, is effective for improving skin viscoelasticity. While its effect on hydration is more pronounced in dry skin, the therapy significantly enhances skin elasticity, supporting its use as a preventative and corrective treatment for age-related changes, including progressive loss of skin density and firmness. c 2025151876  
11 January 20  
Royal Spas in France, it was initially employed to treat obliterating arteriopathies. Over the years, its application has expanded to aesthetic medicine, particularly in the treatment of periorbital concerns such as fine lines and hyperpigmentation. Subcutaneous injections of CO2, administered weekly over seven weeks, have demonstrated significant improvements in these parameters. Carboxytherapy's physiological effects include inducing a controlled oxygen deficit, which triggers an increase in blood flow and the release of growth factors such as vascular endothelial growth factor (VEGF). This stimulation promotes angiogenesis, enhancing cutaneous microcirculation and vasomotion [1]. Local hypoxia caused by the administration of carbon dioxide during carboxytherapy is a strong stimulus for angiogenesis, triggered by the release of angiogenic factors from hypoxic tissues [2; 3; 4]. As a result, tissue perfusion and lymphatic circulation increase, improving tissue drainage. The rise in blood pressure and dilation of blood vessels following carbon dioxide administration enhances nonurishment, oxygenation, and regeneration in the treated area, translating into a general improvement in skin function [1; 3]. Carboxytherapy appears to improve hydration and skin viscoelasticity by increasing the water content of the skin. Tissue trauma caused by the rapid flow of carbon dioxide induces localized, controlled inflammation, facilitating connective tissue remodeling. Old collagen fibers are degraded, while the synthesis of new fibers is enhanced, leading to a more organized and compact structure. This process increases skin thickness and elasticity. Furthermore, carboxytherapy promotes an increase in the number of collagen fibers and improves their structure, including increased diameter [5]. Studies have demonstrated that carboxytherapy can thicken the epidermis and improve skin structure. For instance, [PERSON] et al. observed epidermal thickening through histopathological analysis [6; 7; 8], while [PERSON] et al. reported significant epidermal thickening after six sessions of carboxytherapy for acne scars [9]. These findings suggest that carboxytherapy-induced epidermal remodeling may also enhance skin hydration and reduce transepidermal water loss (TEWL). The relationship between transepidermal water loss (TEWL) and the structural integrity of the skin barrier is well-documented, with TEWL playing a critical role in the development of skin dryness. It is hypothesized that the epidermal thickening induced by carboxytherapy could improve water retention and consequently reduce TEWL [10].