Various methods by which hands are cleaned, including handwashing with plain and antimicrobial soaps and the use of alcohol-based hand rubs. Hand hygiene is the single most effective method of decreasing nosocomial infections. The Centers for Disease Control and Prevention states that if hands are not visibly soiled, alcohol preparations containing between 60% and 90% ethanol or isopropanol kill microorganisms more effectively than plain or antimicrobial soap and are not as harsh. After the hand rub is applied to the palm of one hand, the hands and fingers should be rubbed together, covering all surfaces, until they are entirely dry. Hands that are visibly dirty or contaminated should still be washed with soap and water for at least 15 seconds. The need for hand hygiene is not eliminated by the use of gloves. Contact dermatitis caused by alcohol hand rubs is very uncommon. However, with increasing use of such products by health care personnel, true allergic reactions will occasionally be encountered. Hospital computers can serve as a reservoir for drug-resistant bacteria such as vancomycin-resistant Enterococcus faecium (VRE), methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa.