Put simply, it makes more sense to use vitamin C in the daytime, when your skin is more likely to be exposed to things such as infrared and pollution which can lead to skin damage. Because of its antioxidant ability to shield skin from said environmental aggressors, Dr Wedgeworth suggests it might not be the best move to use it solely as part of an evening routine. Why? Because your face is essentially just hitting your pillow. London-based consultant dermatologist Dr Justine Kluk expanded: "Further benefits of vitamin C include reduction in collagen breakdown leading to tighter, firmer skin and a brighter, more even skin tone. As such, it makes good sense to take advantage of these benefits in the morning in order to boost the defence barrier provided by our sunscreens." R29 recommends Clinique's Fresh Pressed Daily Booster With Pure Vitamin C 10%, £25 , or Kiehls' Powerful Strength Line-Reducing Concentrate, £49.50