▁b acter ia ▁res iding ▁in ▁the ▁deeper ▁areas ▁of ▁the ▁hair ▁fol lic le , ▁gut ▁and ▁u ro gen ital ▁open ings . ▁ ▁C lin ical ▁significance ▁ ▁D ise ases ▁of ▁the ▁skin ▁include ▁skin ▁in fe ctions ▁and ▁skin ▁ne op las ms ▁( including ▁skin ▁cancer ). ▁ ▁D erm at ology ▁is ▁the ▁branch ▁of ▁medicine ▁that ▁de als ▁with ▁conditions ▁of ▁the ▁skin . ▁ ▁Society ▁and ▁culture ▁ ▁H yg iene ▁and ▁skin ▁care ▁ ▁The ▁skin ▁supports ▁its ▁own ▁e cos ystem s ▁of ▁micro organ isms , ▁including ▁ye asts ▁and ▁b acter ia , ▁which ▁cannot ▁be ▁removed ▁by ▁any ▁amount ▁of ▁clean ing . ▁Est im ates ▁place ▁the ▁number ▁of ▁individual ▁b acter ia ▁on ▁the ▁surface ▁of ▁one ▁square ▁in ch ▁( 6 . 5 ▁square ▁cm ) ▁of ▁human ▁skin ▁at ▁ 5 0 ▁million , ▁though ▁this ▁figure ▁var ies ▁greatly ▁over ▁the ▁average ▁ ▁of ▁human ▁skin . ▁O ily ▁surfaces , ▁such ▁as ▁the ▁face , ▁may ▁contain ▁over ▁ 5 0 0 ▁million ▁b acter ia ▁per ▁square ▁in ch ▁( 6 . 5   cm ²). ▁Despite ▁these ▁vast ▁quantities , ▁all ▁of ▁the ▁b acter ia ▁found ▁on ▁the ▁skin ' s ▁surface ▁would ▁fit ▁into ▁a ▁volume ▁the ▁size ▁of ▁a ▁pe a . ▁In ▁general , ▁the ▁micro organ isms ▁keep ▁one ▁another ▁in ▁check ▁and ▁are ▁part ▁of ▁a ▁health y ▁skin . ▁When ▁the ▁balance ▁is ▁dist