Exploring the potential of Portuguese thermal spring water as an ingredient for cosmetic formulations

Abstract

Thermal spring waters (TSW), utilized for centuries for their health benefits, are increasingly recognized scientifically for their therapeutic potential. These are largely attributed to their unique mineral compositions derived from long-term water-rock interactions. Properties like immunomodulation, antioxidant activity, and skin barrier reinforcement have spurred interest in TSW within the cosmetics industry, driven by consumer demand for natural and effective ingredients. This thesis aims at investigating the cosmetic potential of TSW from Chaves, Portugal, a historically recognized spring whose properties remained scientifically underexplored. The initial phase characterized Chaves TSW and evaluated its dermatological bioactivities. In vitro studies revealed anti-inflammatory potential, evidenced by reduced IL-6 levels in human keratinocytes (HaCaT) exposed to urban pollutants, alongside with anti-elastase activity. A clinical study on 23 human volunteers demonstrated that Chaves TSW significantly improved skin hydration on dry skin volunteers and reduced transepidermal water loss (TEWL), suggesting skin barrier enhancement without disrupting the resident skin microbiota. Based on these positive skin findings, a cosmetic formulation incorporating Chaves TSW was developed with a high natural index (96% based on ISO 16128). The research scope was extended to evaluate the effects on hair, a less common application for TSW. While Chaves TSW alone did not significantly alter bleached hair fiber’s properties, the formulation improved hair combability, likely due to included surfactants. Conversely, the formulation decreased the thermal denaturation temperature of hair keratin, potentially linked to surfactant-keratin interactions observed via DSC and ATR-FTIR analyses. Finally, the base formulation's potential was further explored by incorporating Mallow (Malva sylvestris); endemic to the region; and Cucumber (Cucumis sativus) extracts, known for their skin benefits, such as antioxidant potential. Three formulations containing both extracts and a mixture of both were developed, and subsequent testing revealed significantly improved bioactivities. Notably, a strong synergistic Fe2+ chelating capacity emerged, exceeding that of the formulation's chelating agent alone. This correlated with enhanced antioxidant activity and significantly increased inhibition of the age-related enzymes collagenase and tyrosinase, likely due to cofactor chelation. The combination of extracts also yielded potent elastase inhibition. Furthermore, the anti-inflammatory effects were re-evaluated using a mixture containing TSW extracts, and sodium phytate (chelating agent), which nonetheless exhibited anti-inflammatory properties like those of water but effectively reducing IL-1α levels. In conclusion, this work validates the beneficial properties of Chaves TSW for skincare, particularly its anti-inflammatory and barrier-reinforcing effects. It further demonstrates that formulating TSW, especially when enhanced with synergistic natural extracts like Mallow and Cucumber, can create multifunctional cosmetic ingredients with significantly amplified antioxidant, anti-enzyme, and anti-inflammatory activities, offering promise for advanced skin and potentially scalp care applications.

Date of Award	22 Dec 2025
Original language	English
Awarding Institution	Universidade Católica Portuguesa
Supervisor	Ana Raquel Madureira (Supervisor) & Sílvia Pedrosa (Co-Supervisor)