SUPPLEMENT ARTICLE: Scientific and Clinical Insights into the Facial Application of Mineralizing Volcanic Water

manganese, molybdenum, iodine, bromine, and selenium) make up less than 0.02% of the body mass (Table 1). Although these elements account for a minute amount of total body weight, they play vital roles in biological systems.⁵ By binding to molecules on the receptor site of cell membranes or alternating the membrane structure to prevent the entry of specific molecules, trace elements control critical biological functions (eg, catalyze enzymes). In addition, trace elements in sufficient quantities stabilize cellular structures,⁵ but imbalances in their optimum levels adversely affect biological processes and are associated with intrinsic and extrinsic aging and skin disorders and diseases.^6,7 Mainly, the skin loses its minerals through perspiration via the skin, lungs, and airways.

Previous studies have shown that dissolved substances in some natural thermal waters have beneficial effects for supporting skin health, including anti-inflammatory actions.⁸ Therefore, the skin may benefit from topical application of trace elements present in thermal water. However, the mechanisms underlying these actions are not fully understood. Molecular permeation through the SC is dependent on diffusion, which occurs through a dynamic exchange between the molecules present within the membrane.³ The corneocytes have a polar interior and may be obstacles to the diffusive transport of hydrophobic molecules. At the same time, they may provide an additional transport route for more polar compounds such as water.^3,4 The SC lipids may also be affected by increased hydration, which increases SC permeability.^3,4

In vitro experiments of percutaneous migration indicate that the number of elements transferred across the skin depends on their concentration in mineral water. Research has demonstrated that several elements can cross the skin in as little as twenty minutes following topical application. Notably, the amounts transferred were compared with toxicological guidelines and worldwide daily requirement models. The data indicate that none of these elements reach concentrations so high as to represent hazardous conditions.⁹ The skin's protective barrier helps keep foreign chemicals out of the body; however, if the skin is cracked or cut, chemicals can penetrate more easily. While exploring its potential clinical benefits, it is necessary to differentiate the minerals in mineralizing volcanic water-containing serum (MVW).

The Role of the Panel
An expert panel of seven dermatologists and two clinical researchers specializing in aesthetic and dermatological indications reviewed and discussed publications on the topic at hand. Two virtual advisory board meetings were held between February and May 2021. The first advisory board aimed to explore the exposome related to skin health and aging. The second advisory board investigated clinical and scientific data on MVW related to the protection against the harmful effects of the exposome and clinical benefits it could present for facial dermatoses (eg, rosacea-prone skin) and post-procedural healing. The results of the two advisory boards, coupled with expert opinion and the outcome of the updated systematic literature review, informed the statements on which the advisors reached a consensus (>80% agreement; Table 2).

Literature Review
The post-meeting literature review included publications relevant to essential elements and skin health, with a particular focus on clinical studies investigating the use of MVW. Searches were conducted in August 2021, using PubMed as the primary search engine and Google Scholar as a secondary source. In addition, we culled publications in English published between January 2010 and July 2021. Box 1