The literature describes niacinamide, but also postbiotics and peptides, as ingredients that improve skin barrier function, but also affect melanin and sebum levels in individuals. However, the combined effects of these ingredients in a single cosmetic serum have not been sufficiently investigated. Therefore, the aim of this randomized controlled study, conducted at the University of Split School of Medicine (Croatia), was to evaluate the effects of cosmetic products containing these active ingredients. This study was registered with ClinicalTrials.gov (NCT06189105) and has been completed. Primary outcomes were the levels of trans epidermal water loss, skin hydration, erythema, melanin, and sebum, all measured in 25 healthy Caucasian participants. Significant differences between hydration levels were observed at week 4 (61.0 ± 11.2 vs. 68.6 ± 13.3 AU, control and intervention). Moreover, a significant decrease in erythema values from the first to last measurement in the intervention group was observed, (379.9 ± 106.8 vs. 333.6 ± 73.5 AU, baseline values and week 4, intervention group). Interestingly, both the increase in skin hydration levels and the decrease in skin erythema after niacinamide serum application were significant in study participants who did not use sun protection products. It is well known that ultraviolet radiation has detrimental effects on human skin, and our results suggest that niacinamide could help counteract these effects.

Contact dermatitis is a common inflammatory skin disease that often requires prescription therapy and is associated with adverse reactions. Omega fatty acids have been recognized for their anti-inflammatory effect and could serve as a safer option in contact dermatitis treatment. Therefore, the aim of this randomized controlled study, conducted at the University of Split School of Medicine, was to evaluate the efficacy and safety of omega fatty acids containing topical products in an experimental model of irritant contact dermatitis. This study was registered with ClinicalTrials (NCT06189144) and is closed. The primary outcomes were levels of transepidermal water loss, skin hydration, and skin erythema, all measured using an MPA6 device in 25 healthy participants. A significant difference was observed between the hydration values of the intervention (45.7 ± 12.4) and control groups (31.6 ± 12.3) (p < 0.05) on final measurements (day 10). Moreover, higher erythema levels were observed in participants who were smokers, compared to non-smokers. No adverse drug reactions were observed during the study period. In conclusion, omega fatty acids topical product use shows promise in the treatment of irritant contact dermatitis, and further studies are needed to evaluate efficacy in a larger sample of patients.