Early detection of microcomedones induced by cocoa butter using reflectance confocal microscopy

Background Many ingredients used in cosmetics evoke a comedogenic response. The concept of ‘‘acne cosmetica’’ was developed to link the use of certain ingredients to comedone formation. Various clinical research methods have been suggested for the effective screening of an ingredient that can worsen acne or acneiform eruption and confirm its clinical relevance as to whether it is used as a non‐comedogenic claim. Although comedogenicity assessment has not yet been established, attempts have been made to evaluate the comedogenicity of cosmetic ingredients and find the most appropriate method to evaluate comedogenicity in human skin. Materials and methods Total 6 participants were included in the study. Each participant received patches on the upper back containing cocoa butter. We used reflectance confocal microscopy (RCM) to count the number of microcomedones and follicles induced by cocoa butter. Results The mean value change of microcomedone/follicle by the comedogenic substance was significantly higher than that of the non‐applied site for 2 weeks (p = 0.0419). The mean value changes of the microcomedone diameter caused by the comedogenic substance were significantly larger than those found at the non‐applied site at 2 and 4 weeks (p = 0.0026 and p = 0.0038, respectively). Conclusions We recommend RCM as a non‐invasive real‐time method that is useful for evaluating comedogenicity and early detection of a microcomedone.