Defined as hand washing or washing hands with soap and water or using a waterless hand sanitizer.
Hand hygiene is central to preventing spread of infectious diseases in home and everyday life settings.
In situations where hand washing with soap is not an option (e.g. when in a public place with no access to wash facilities), a waterless hand sanitizer such as an alcohol hand gel can be used. They can also be used in addition to hand washing, to minimise risks when caring for “at risk” groups. To be effective, alcohol hand gels should contain not less than 60%v/v alcohol. Hand sanitizers are not an option in most developing countries; in situations where availability of water is a problem, there are appropriate solutions such as tippy-taps, which use much less water and are cheap to make.
Hand washing for hand hygiene is the act of cleaning the hands with or without the use of water or another liquid, or with the use of soap, for the purpose of removing soil, dirt, and/or microorganisms.
Medical hand hygiene pertains to the hygiene practices related to the administration of medicine and medical care that prevents or minimizes disease and the spreading of disease. The main medical purpose of washing hands is to cleanse the hands of pathogens (including bacteria or viruses) and chemicals which can cause personal harm or disease. This is especially important for people who handle food or work in the medical field, but it is also an important practice for the general public. People can become infected with respiratory illnesses such as influenza or the common cold, for example, if they don’t wash their hands before touching their eyes, nose, or mouth. Indeed, the Centers for Disease Control and Prevention (CDC) has stated: “It is well documented that one of the most important measures for preventing the spread of pathogens is effective hand washing.” As a general rule, handwashing protects people poorly or not at all from droplet- and airborne diseases, such as measles, chickenpox, influenza, and tuberculosis. It protects best against diseases transmitted through fecal-oral routes (such as many forms of stomach flu) and direct physical contact (such as impetigo).
In addition to hand washing with soap and water, the use of alcohol gels is an effective form of killing some kinds of pathogens.
Source and References http://en.wikipedia.org/wiki/Hand_washing