'Drink more water for better skin' is the most-repeated and least-supported skincare advice. Adequate hydration is necessary for normal body function, but unless you're meaningfully dehydrated, drinking extra water has no measurable effect on skin appearance.
What hydration actually does
Skin gets its water from the bloodstream. The body prioritises water for organs that need it most (heart, brain, kidneys). Skin is one of the last to receive surplus. Once basic body needs are met, additional water excretes rather than topping up the skin specifically.
Studies on water intake and skin appearance show mild improvements in barrier function (transepidermal water loss) at the very lowest intake levels — those who are genuinely under-hydrated. No measurable benefit above the threshold of normal hydration.
What does affect skin hydration
Topical humectants (hyaluronic acid, glycerin, urea) that draw water into the stratum corneum. Occlusives (squalane, petroleum, ceramide-rich creams) that prevent water evaporating. Indoor humidity — running a humidifier at 40-50% in heated rooms does more than drinking another glass of water.
How to read your own hydration status
Urine colour: pale yellow = adequate; clear = over-hydrated (unnecessary); dark yellow = drink more. Most adults need around 1.5-2 litres daily including from food and other drinks. Coffee and tea count toward total intake (the diuretic effect is mild and offset by the water in them).
Drink enough to keep urine pale yellow, then put the focus on topical hydration. Water is necessary for life, not magical for skin.