Does drinking 8 glasses of water a day keep my skin moist?
No. Despite years of having this drummed into our heads, this is not true. It is good to keep your body, including your skin, hydrated, however the outermost layer of skin does not absorb water since it is made up of dead skin cells. Moisture level of skin is not determined by internal factors, but rather external ones, such as cold or hot air, dry heat and by the number of oil-producing glands you have. So if you want to hydrate your skin, exfoliate it weekly with a sea-salt scrub or other exfoliator to remove dead skin then apply a rich moisturizer while skin is still damp. Want to hydrate your insides then by all means, drink your 8 glasses of water a day.
source : beauty.about.com
source : beauty.about.com