It depends on the persons oil glands , activity rate , and sensitivity . If the person works out , and keeps their body heavily moisturized , probably 2 a day . If they are rather inactive , they should probably just take 1 . It also depends what soap , shampoo , etc . they use . Some can dry you skin out worse than it may already be if they use the product too much . If your hair is really dirty , or gets oily easily , you may want to use a clarifying shampoo.
So it does depend all on the person , product , and even the water , because too hot of water can dry you out , ut too cold can be dangerous to your breathing it you aren't used to it .