The skin, the largest organ of the human body, plays numerous important roles, with its protective function being one of the most crucial. This is directly related to the fact that the skin acts as a barrier between the internal and external environments of the body. It protects the body from various external factors, excessive water evaporation, and the penetration of substances into the skin. In this context, the stratum corneum, the outermost layer of the epidermis, plays a key role. It also significantly influences the skin’s appearance, making it relevant from a cosmetic perspective.
The beneficial effects of the microalgae Dunaliella species extract on skin properties have already been confirmed in previous studies. In this thesis, we incorporated the extract into cosmetic formulations and observed the effects of a hydrophilic cream and liquid crystals, both with and without the incorporated algae extract, on selected skin parameters in 15 female volunteers over a 14-day period. Additionally, we monitored the effects of pre-toning the skin with saline solution, followed by the application of formulations containing the algae extract. The skin condition was evaluated using non-invasive instrumental methods. Specifically, we measured changes in transepidermal water loss (TEWL), melanin and erythema index, skin hydration, pH, and biomechanical skin parameters.
In our study, we observed an increase in TEWL after using the liquid crystal-based or classical emulsion gel products, as well as with the concurrent use of saline. This contradicts previous findings and also the results of the erythema index measurements. The lowest erythema values were recorded after skin treatment with saline and the hydrophilic cream containing the algae extract. After two weeks of using the hydrophilic cream, both with and without the algae extract, an increase in skin hydration was observed in the volunteers, even when saline was used beforehand. This effect was not observed with the liquid crystal-based products. However, these products had a more favorable effect on skin pH, which did not change or slightly decreased after application. In some samples, we also detected a positive influence on selected biomechanical parameters of the skin.
The results of this thesis confirm the beneficial effects of using a moisturizing cream containing Dunaliella species microalgae extract as a cosmetically active ingredient in combination with saline. Most importantly, they contribute significantly to the further development of cosmetic formulations for skin care from a microstructural perspective.
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