The lips form the barrier between the exterior and interior of the human organism. They participate in speech, facial expressions, and eating, and they also have an impact on an individual's self-esteem. The stratuum corneum of the vermillion zone of the lip differs from the regular stratuum corneum in its lipid composition, hydration, thickness, roughness, blood supply, desquamation rate, and melanin content. These differences contribute to the increased susceptibility of lip skin to damage caused by UV radiation. Compared to the skin elsewhere on the face, the skin of the lips receives the highest amount of UV radiation. The effects of UV overexposure are similar to those on regular skin and lead to the development of basal cell carcinoma, squamous cell carcinoma, actinic cheilitis, Herpes simplex labialis, and other pathological conditions. Protecting the lips with sunscreen lip balms is crucial in preventing such diseases.
In this diploma thesis we reviewed the ingredients of 95 sunscreen lip balms available on the Slovenian market, both in physical stores and on online retail websites, and assessed their safety based on their compliance with legislation and the ingredients they contain. The work focuses on UV-filters, which are the active ingredient, but also includes a review of ingredients with a higher health risk: colorants, fragrances and substances used to ensure stability. We noted 15 different UV-filters, 18 different colorants, 28 fragrances and 34 different substances used to ensure stability. Some ingredients present are well-established, such as UV-filters butyl methoxydibenzoylmethane (in 58.9 % of products) and ethyhexyl triazone (in 46.3 % of products), colorant mica (in 7.4 % of products), titanium dioxide (in 12.6 % of products as an UV-filter and in 23.2 % of products as a colorant), preservative phenoxyethanol (in 7.4 % of products) and antioxidant tocopherol (in 66.3 % of products). Some, like UV-filters homosalate (in 8.4 % of products), benzophenone-3 (in 9.5 % of products) and octocrylene (in 27.4 % of products), colorants iron oxides (CI 77491 in 15.8 % of products and CI 77492 in 11.6 % of products), fragrances vanillin (in 16.8 % of products) and limonene (in 25.3 % of products), antioxidant butylated hydroxytoluene (in 16.8 % of products), and preservative benzyl alcohol (in 10.5 % of products), pose a higher health risk. None of the included products contain prohibited substances. Considering the results obtained and the toxicological profiles of selected ingredients, it can be concluded that the reviewed products are compliant with safety standards and their purpuse of use.
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