The skin of hands is permanently colonised with what is termed the   resident or normal microbial flora.  This comprises various microorganisms e.g. coagulase negative staphylococci and various diphtheroids, that live in the hair follicles and the ducts of the sebaceous glands and sweat glands. They are harmless (often termed “commensal”) microorganisms  to healthy people.  They gradually exit from these sites onto the rest of the hand surfaces and are then lost  each day as skin scales (the major part of household “dust”). It estimated that we lose about between 30,000 and 40,000 scales every hour. This normal commensal skin flora can be dangerous in  immunocompromised patients, as well as in others where there has been an opportunity for them to by-pass the normal host defenses such as during  invasive procedures e.g. insertion of an intravenous line or performance of surgery. 

This flora can never be completely removed from the hands when they are washed with soap and water, but it can be significantly reduced with hand hygiene products containing disinfectants (see below). 

During different activities hands may become visibly dirty (“soiled”), as a result of care activities most often from patients’ body fluids or excretions. Also, hands of healthcare workers may be contaminated by microorganisms that colonize patients or contaminate the environment, and such microorganisms can survive on the skin of the hand for about 2-60 minutes. This is the so-called transient flora of the hand skin. In the absence of hand hygiene the level of microbial contamination of healthcare workers hands during work processes steadily increases.