Vitamin C , also known as ascorbic acid, is an antioxidant that works to neutralise free radicals [ pollution, smoke, UV rays] that can break down the collagen in your skin , causing more visible signs of ageing.
Alongside your sunscreen, it helps to protect the skin from the harmful effects of UV rays
[ but it is not a sunblock] by reducing the appearance of sunspots, discolouration, refining skin texture and lessening the appearance of existing wrinkles.
When should you apply Vitamin C?
Since it helps to neutralise free radicals and protect from UV rays it should be applied in the mornings . Cleanse skin first, apply your Vitamin C [ either in drops or as a serum]
Then apply your broad spectrum sunscreen on top.
How should Vitamin C be stored?
The stability of Vitamin C can be a concern because exposure to air, heat & light can cause it to oxidise [ go brown]
Look for ascorbic acid combined with other antioxidants [ e.g Vitamin E added , makes Vitamin C four times more potent]
Also look for packaging that protects the solution from air and light e.g dark glass bottles, or vials that close tightly
One tried and true favourite of mine that fits this criteria :
Ever active C & E + peptide serum: