Alcohols for Skin Antisepsis at Clinically Relevant Skin Sites

The antiseptic efficacy of ethanol, isopropanol, and n-propanol at 60%, 70%, and 89.5% (all vol/vol) was analyzed after 2, 3, or 4 min of application to the forehead, back, and abdomen of 180 volunteers by the use of a standardized swab sampling method. Results of recolonization by the aerobic skin flora of the upper arms and backs of 20 volunteers were compared 72 h after treatment with 0.5%, 1%, or 2% chlorhexidine digluconate (CHG) in 89.5% n-propanol. The most effective alcohol at all skin sites was n-propanol, with a mean log₁₀ reduction of 1.82 after 2 min on the forehead. Efficacy against the aerobic flora of the forehead was mainly influenced by the type of alcohol (P < 0.001), followed by the concentration (P < 0.001) and the application time (P = 0.006). Ethanol and isopropanol were significantly less effective (both P < 0.001). Alcohol supplemented with 0.5% or more CHG was significantly more effective than alcohol alone in the suppression of recolonization (P < 0.05). An 89.5% solution of n-propanol was the most effective alcohol for the reduction of populations of aerobic skin flora. Its combination with CHG is appropriate whenever recolonization of the skin must be limited. Further studies are needed to determine the most effective concentration of CHG in n-propanol to provide the best protection against recolonization of the skin, e.g., for catheter site care.In the United States and Europe, both ethanol and isopropanol are recognized active agents in medicinal products (7, 32), e.g., to prevent surgical-site infections as recommended by the Centers for Disease Control and Prevention (CDC). The U.S. Food and Drug Administration (FDA) assessed aqueous ethanol at 60% to 95% and isopropanol at 70% to 91.3% (vol/vol) as safe and effective for patient preoperative skin preparations (9). In Europe, n-propanol is also approved as an active ingredient in medicinal products for skin antisepsis.For catheter site care, the CDC strongly recommends the use of a 2% chlorhexidine-based preparation (24). The suppression of the recolonization of the catheter site is important because of the permanent gap in the skin barrier and the long intervals between dressing changes. Chlorhexidine is more effective than other standard preparations in preventing catheter colonization when used for catheter site care (33). It is also more effective in reducing bloodstream infection rates, which are the most important clinical endpoints (6, 19, 22).To the best of our knowledge, the levels of efficacy of the three alcohols used for skin antisepsis have never been studied systematically in vivo. Therefore, in this study, ethanol, isopropanol, and n-propanol were compared at three different concentrations and for three different application times at four clinically relevant skin sites to determine which of these antiseptic treatments is most effective in reducing the populations of aerobic skin flora. We then combined the most effective alcohol solutions identified with different concentrations of chlorhexidine digluconate (CHG) and analyzed their effects on recolonization at two different skin sites after 72 h of sterile coverage.