Characterization of percutaneous absorption of calcium, magnesium, and potentially toxic elements in two tailored sulfurous therapeutic peloids: a comprehensive in vitro pilot study

Abstract

Pelotherapy treatments in thermal spas, which utilize peloids composed of clay minerals mixed with saltwater or mineral-medicinal water, can have various effects on spa users, ranging from therapeutic to potential adverse reactions. Despite the widespread use of peloids, comprehensive information on the penetration and permeation of essential and potentially toxic elements into deeper layers of the skin during pelotherapy is limited. Understanding the concentrations of these elements is crucial for evaluating therapeutic benefits and ensuring safety. This study investigates the in vitro availability and absorption of calcium, magnesium, and potentially toxic elements in two peloids, considering their formulation matrix. To replicate the pelotherapy methodology, an in vitro permeation experiment was conducted using a vertical diffusion chamber (Franz cells) and a biological system with human skin membranes from five Caucasian women, age range between 25 and 51 years. The experiment involved heating the peloids to 45℃. The results emphasize the possible transport properties of chemical elements in peloids, providing valuable information related to potential therapeutic efficacy and safety considerations. Despite no apparent differences between peloids’ chemical composition, the method identified permeation variations among chemical elements. The methodology employed in this study adheres to the guidelines outlined by OECD for analyzing skin absorption through an in vitro approach. Furthermore, it aligns with the associated OECD guidance document for conducting skin absorption studies. The replicability of this methodology not only facilitates the analysis of peloids pre-formulation but also provides a robust means to evaluate the effectiveness of therapeutic elements during topical administration, particularly those with potential toxicity concerns.

Natural peloids originating from subsea depths of 200 m in the hupo basin, South Korea: physicochemical properties for potential pelotherapy applications

“…During the therapeutic application of peloids, they come into contact with the skin, potentially exposing individuals to various toxic metals. Despite the skin’s protective function, studies have shown that it can still permit the penetration of chemicals, including heavy metals (Kezic & Nielsen, 2009 ; Lim et al, 2018 ), which suggests that dermal contact serves as a route for exposure to heavy metals present in peloids, posing inherent health risks (Bastos et al, 2024 ). Pb and Cd in the human body has been linked to several severe health conditions, including cancer, kidney disorders, skeletal damage, brain damage, and reproductive failure (Miranzadeh et al, 2023 ).…”

“…Several studies on the dermal bioavailability of these heavy metals have also been conducted on peloids. Through in vitro permeation experiments using Turkish peloid, the skin permeability of certain heavy metals was observed, and it was also noted that the amount of heavy metals able to migrate through the skin layer after application of the peloids was below acceptable levels (Bastos et al, 2024 ). Additionally, Carretero et al ( 2010 ) reported that potentially toxic elements were leached only in very low concentrations or not at all by artificial sweat.…”