<P> It is important to note that the human skin is host to numerous bacterial and fungal species, some of which are known to be harmful, some known to be beneficial and the vast majority unresearched . The use of bactericidal and fungicidal soaps will inevitably lead to bacterial and fungal populations which are resistant to the chemicals employed . (see Drug resistance) </P> <P> Skin flora do not readily pass between people: 30 seconds of moderate friction and dry hand contact results in a transfer of only 0.07% of natural hand flora from naked with a greater percentage from gloves . </P> <P> The most effective (60 to 80% reduction) antimicrobial washing is with ethanol, isopropanol, and n - propanol . Viruses are most affected by high (95%) concentrations of ethanol, while bacteria are more affected by n - propanol . </P> <P> Unmedicated soaps are not very effective as illustrated by the following data . Health care workers washed their hands once in nonmedicated liquid soap for 30 seconds . The students / technicians for 20 times . </P>

What characteristics of the skin tend to limit infectious disease