<P> The term skin flora (also commonly referred to as skin microbiome) refers to the microorganisms which reside on the skin; typically human skin . </P> <P> Many of them are bacteria of which there are around 1000 species upon human skin from 19 phyla . Most are found in the superficial layers of the epidermis and the upper parts of hair follicles . </P> <P> Skin flora is usually non-pathogenic, and either commensal (are not harmful to their host) or mutualistic (offer a benefit). The benefits bacteria can offer include preventing transient pathogenic organisms from colonizing the skin surface, either by competing for nutrients, secreting chemicals against them, or stimulating the skin's immune system . However, resident microbes can cause skin diseases and enter the blood system, creating life - threatening diseases, particularly in immunosuppressed people . </P>

Where do the resident microorganisms reside in the skin