Vitamin
C
Vitamin C earns its place in the morning: it works alongside sunscreen, not instead of it. At 20% it is a strong serum, so we tell people to patch test and build up — a little tingle on day one is normal, stinging is not.
It interrupts the pigment pathway, so dark marks and dullness fade gradually with daily use.
As an antioxidant it mops up free radicals from UV exposure and pollution before they damage collagen.
Vitamin C is a cofactor in collagen synthesis; over months skin looks a touch firmer and more even.
Expect brightness first, in about 3–4 weeks. Dark marks take longer — 8–12 weeks of daily morning use under SPF.
Benzoyl peroxide in the same step. It oxidises vitamin C on contact and cancels most of the benefit. Use them at different times of day.
