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Background: Contact dermatitis (CD) is a prevalent inflammatory skin condition, with diagnostic challenges in distinguishing allergic (ACD) from irritant contact dermatitis (ICD). This study aimed to explore cholesterol-derived biomarkers as potential diagnostic tools. As cholesterol derivatives play key roles in skin barrier integrity and inflammation, they are promising candidates for assessing skin barrier disruption in CD. Methods: Stratum corneum samples were collected by tape stripping from experimentally induced and chronic lesions, as well as healthy non-lesional skin. Biomarkers Cholesterol Sulfate (Chol-Sulf), Cholesterol Glucosyl (Chol-Glc) and their ratio were quantified. Data were analyzed using ANOVA, Pearson’s correlation, logistic regression and ROC curves. Results: Chol-Glc and the Chol-Glc/Chol-Sulf ratio differed significantly across the diagnostic groups, while Chol-Sulf did not. Logistic regression and ROC analyses revealed a limited standalone diagnostic accuracy for the individual biomarkers (all AUC < 0.6). Conclusions: Chol-Glc and the ratio exhibit disease-specific patterns relevant for subtype discrimination. Although insufficient as independent diagnostic tools, these markers may contribute to future multivariate diagnostic models for CD diagnosis.

IntroductionSquamous cell carcinoma and multiple actinic keratoses caused by solar ultraviolet radiation (UVR) are among the most frequently recognised occupational diseases in Germany. Employees who regularly work outdoors, for example, in the construction industry, agriculture, forestry and gardening, are at a higher risk of developing occupational skin cancer. However, sun-safety behaviour in outdoor workers is currently insufficient. Therefore, this study aims to investigate the effectiveness of an intervention to increase sunscreen use among outdoor workers.Methods and analysisIn this non-randomised, controlled intervention study, 234 outdoor workers from different companies in industries with outdoor working activities based in Germany will be included. The study population, aged 18 years and above, has to be intensively exposed to solar UVR of regularly 1 hour or more per day. The intervention group will receive a sunscreen package as well as health education. The control group follows the practice in their companies (‘treatment-as-usual’). At the beginning of the study, after 3 months and at the end of the study (after 6 months), both groups filled in different questionnaires. In addition, stratum corneum (SC) samples will be collected at the beginning and after 3 months. The primary outcome—increase in the frequency of sunscreen use during work and in leisure time—will be assessed from data on self-reported sunscreen use. The secondary outcomes include sun protection behaviour, knowledge about sun protection and skin cancer, and acceptance of the provided sunscreens. Further secondary outcomes include internal UV dose and UV-related immune response, determined by the levels of SC biomarkers. Data will be analysed using both descriptive and inferential methods.Ethics and disseminationThe study protocol followed the principles of the Declaration of Helsinki (2013) and was approved by the Ethics Committee of Osnabrück University, Germany (reference Ethik-37/2024). Study results will be disseminated through peer-reviewed publications and conference presentations.Trial registration numberDRKS00035178.

This study compared three multiplex immunoassay platforms, Meso Scale Discovery (MSD), NULISA, and Olink, for detecting protein markers in stratum corneum tape strips, a non-invasive sampling method challenged by low protein yield. We evaluated 30 shared proteins across all three platforms, plus 9 additional proteins shared only between MSD and NULISA, and 1 between MSD and OLINK, using samples from non-lesional skin and skin affected by patch test-induced irritant and allergic contact dermatitis, and clinical hand dermatitis. Proteins were considered detectable when more than 50% of samples exceeded the platform’s protein-specific detection limit. MSD demonstrated the highest sensitivity, detecting 70% of shared proteins, followed by NULISA (30%) and Olink (16.7%). Four proteins, CXCL8, VEGFA, IL18, and CCL2, were detected by all three platforms with interclass correlation coefficients ranging from 0.5 to 0.86. The three platforms exhibited similar differential expression patterns between control and dermatitis-affected skin, supporting overall concordance. MSD uniquely provided absolute protein concentrations, enabling normalization for variable SC content, while NULISA and Olink required smaller sample volumes and fewer assay runs. Generalizability to other diseases and biomarkers requires further investigation.