Antifungal and Safety Assessment of a Natural Topical Formulation Based on Lamiaceae Essential Oil and Sulfurous Natural Mineral Waters Against Malassezia furfur

Pityriasis versicolor (PV) is a condition of the skin caused by the yeast Malassezia that manifests itself through scaly, well-demarcated patches with a dark, depigmented or erythematous coloration. Recurrence is common, and few treatment alternatives are available in the market. In this study, we aim to develop a body lotion for the improvement of PV skin with natural ingredients, such as essential oils and natural mineral waters. The antimicrobial activity of the selected ingredients was evaluated by the broth microdilution test, the volatile assay and the checkerboard assay. In addition, the cytotoxicity to HaCaT was assessed by the MTT assay. Finally, the most promising ingredients were combined in a formulation for topical application, and its efficacy and safety profile was assessed in vitro. Origanum vulgare essential oil was found to be the most active against M. furfur (MIC 0.625% v/v) and synergic with São Pedro do Sul natural mineral water (SPS NMW), while also being biocompatible with keratinocytes (EC50 < 0.06% v/v). The body lotion that was formulated with the most natural ingredients possible (>95%) and showed great activity against M. furfur, being able to reduce its growth by 100%; in addition, it was found to be a non-irritant in 3D reconstructed skin models.