Well, this is an easy one :>.... . Your body produces essential oils to keep your skin conditioned and supple, if it did not, your skin could not breathe and be as pliant as it is.. . Washing, swimming and likewise causes these oils to be stripped away from your skin and as the largest organ of your body, it takes some time for the oils to be secreted again from the pores of your skin...my daughter calls it "pruney", she suffers from this condition a LOT, since she likes to swim and spend hours in the tub.