From a newspaper column featuring Dr. Paul Donohue-
"DEAR DR. DONOHUE: In winter in cold climates, is it really necessary to take a shower daily? Does showering daily promote better health? Until 75 years ago, not many homes had a bathroom or a shower, and for centuries before that, taking a bath was uncommon. Is it really important to shower daily if one doesn't perspire? - E.F.
ANSWER: It's not necessary to shower daily. It's necessary to shower when the body gets dirty or develops an aroma of overripe fruit. Once a week was enough for our ancestors, and for quite distant ancestors, bathing was even less frequent. Their health didn't suffer. On the other hand, if you do get dirty daily or if you do sweat much, then a daily shower keeps the germ population of the skin to a minimum.
It is necessary to wash hands frequently every day to rid them of germs that can enter the body or be passed to others."