These studies showed that the relationship between the cleansing and the damaging effect on the stratum corneum can be properly assessed only by testing different concentrations. Furthermore, this experimental approach allowed to differentiate the four tested cleansing solutions.

Objective: To determine the antimicrobial activity of a distillate of Hamamelis (Aqua Hamamelidis ), United States Pharmacopoeia (USP) 23, and urea formulated as a topical dermatological preparation that contains both active ingredients. Methods: Using the simple occlusion test and expanded flora test, we conducted in vivo studies in 15 healthy volunteers. We also performed in vitro studies using the agar diffusion test. Results: The occlusion test and expanded flora test demonstrated significant antimicrobial activity for a product containing the Hamamelis distillate (90%) and urea (5%) among other ingredients. The expanded flora test demonstrated significant antimicrobial activity for both Hamamelis distillate and urea. The simple occlusion test showed the same tendency, but results were not significant. The agar diffusion test showed inhibition of Staphylococcus aureus and Candida albicans , among other organisms. Comparison with earlier studies of chlorhexidine digluconate and fuchsine using the same method showed that the antimicrobial activities of Hamamelis distillate and urea were relatively weak. This finding is supported by the weak inhibitory activity observed in the agar diffusion test (using 100% of the finished dosage form). Conclusion: Formulations of Hamamelis distillate and urea are mainly used for their antiinflammatory, hydrating, and barrier-stabilizing effects in dermatitis maintenance therapy. As bacterial colonization has a central role in the pathogenesis of atopic dermatitis and intertrigo, the antimicrobial activity of such products is considered a welcome, added benefit.