Primary aliphatic alcohols are germicidal. Their potency increases but water solubility decreases with chain length until amyl alcohol (6 carbons) is reached. Antimicrobial effect is related to their lipid solubility (damages bacterial membranes) and their ability to coagulate cytoplasmic proteins. However, they do not destroy bacterial spores. Ethyl alcohol (ethanol) and isopropyl alcohol (isopropanol) are the most widely used alcohols. They can be used in concentrations of 30%–90% in aqueous solutions; best results are usually obtained with 70% ethanol or 50% isopropanol. Higher concentrations tend to be less effective. Isopropanol is slightly more potent than ethanol because of its greater depression of surface tension. “Rubbing alcohol” is a mixture of alcohols, with isopropanol as its principal ingredient. It is used as a skin disinfectant and rubefacient. Alcohol-based hand rinses have rapid-acting antiseptic effects. This makes them useful in minimizing the transmission of transient flora acquired from infected patients and reducing nosocomial diseases.