OBJECTIVES: The aim of this exploratory study was to investigate the effect of ethanol, isopropanol and n-propanol on stratum corneum (SC) enzymes and keratinocytes in vitro together with their effects on skin condition and function. METHODS: Activities of kallikrein 5 (KLK5) and phospholipase A2 (PLA2) as well as keratinocyte metabolic activity, interleukin-1α (IL-1α) and tumor necrosis factor-α (TNF-α) were measured in vitro in the presence and absence of the different alcohols. We also measured transepidermal water loss (TEWL), skin capacitance, visual dryness and visual redness on the volar forearms of 25 Caucasian women following application of the alcohols 20 and 100 times per day over a period of 14 days in a clinical study. RESULTS: Reduced activities of KLK5 and PLA2 were observed in the presence of the alcohols. The greatest denaturing effect was always observed for n-propanol (P isopropanol > ethanol. At the high application frequencies, the effect of the different alcohols on transepidermal water loss (TEWL) and skin capacitance was similar, but at the low application frequencies, n-propanol had a significant effect on TEWL and capacitance values (P < 0.05). Equally, n-propanol and isopropanol produced significantly more skin redness at the low application frequencies. CONCLUSIONS: Clearly, isopropanol and n-propanol caused significant SC and keratinocyte perturbation in vitro together with damage to skin condition and function in vivo whereas ethanol did not. As a result, we show that ethanol-based sanitizers are better tolerated by skin, particularly in high-use settings, than other alcohols and should be the active ingredient of choice
