Thermal therapy has gained popularity over the years, and Portugal is one of the richest European countries in mineral therapeutic waters. The interest in the use of these natural mineral waters (NMW) for dermatologic purposes is continuously growing but there is a lack of scientific studies supporting its health benefits. The study aims to investigate the effect of a silica-rich NMW in skin cell homeostasis using two representative cell lines of the epidermis and dermis, keratinocytes and fibroblasts, respectively, in addition to a macrophage cell line. Mouse skin fibroblasts, macrophages and human keratinocytes were exposed to culture medium prepared with NMW. Cell metabolism (MTT or resazurin assays) and cell proliferation (trypan blue exclusion dye assay) were investigated. Migration (scratch-wound assay) and senescence (β-galactosidase activity assay) of fibroblasts were also studied. Exposure to NMW compromised the cell metabolic state of all the cell lines tested. This impairment was more pronounced in skin keratinocytes (60% reduction) relatively to skin fibroblasts (45% reduction) or macrophages (25% reduction). Proliferation of macrophages was reduced threefold upon exposure to thermal water, compared to controls. No differences were observed in migration between fibroblasts exposed to NMW and controls, while a potentiation of senescence of these cells was observed. Our results shed light in the bioactive effects of a silica-rich NMW supporting its therapeutic use. A reduction in both cell metabolism and proliferation of keratinocytes and macrophages supports the empirical clinical benefits of this NMW in hyperkeratotic conditions, such as psoriasis and atopic dermatitis.