Soap pH and the effectiveness of alcoholic hand antiseptics

This study was done to investigate if the pH-value of a soap used for handwashing had any effect on the immediate and the prolonged effectiveness of alcoholic hand disinfectants. One acidic soap (pH = 3.5) and one alkaline soap (pH = 8.5) were tested in combination with 70% and 90% ethanol and alcoholic chlorhexidine. Bacterial counts from the hands of 26 test persons were obtained using the fingerprint method. The fingerprints were taken before and after handwashing, after hand disinfection and after 3 h of wearing sterile latex gloves. The results showed that soap pH did not influence significantly the effectiveness of a subsequent hand disinfection. The combined use of alkaline soap and alcoholic chlorhexidine showed a tendency to smaller variation in bacterial reduction and greater effectiveness. This combination was the only one that led to an increased bacterial reduction after 3 h.