A hand antiseptic, hand disinfectant, hand sanitiser or hand sanitizer is a supplement or alternative to hand washing with soap and water. Many preparations are available, including gel, foam, and liquid solutions. The active ingredient in hand sanitizers may be isopropyl alcohol (isopropanol), ethanol, n-propanol, or povidone-iodine. Inactive ingredients in alcohol rubs typically include a thickening agent such as polyacrylic acid for alcohol gels, humectants such as glycerin for liquid rubs, propylene glycol, and essential oils of plants. Alcohol-based hand sanitizers are more effective at killing microorganisms than soaps and do not dry out hands as much.