Vitamin C is awesome for skin health. It can help reduce inflammation, brighten skin, help reduce the appearance of wrinkles and even fade acne scars. Plus there are lots of independent medical studies which back up these properties. It's a fantastic skin care partner...but it does have one minor flaw - users of vitamin C serums may find themselves with slightly stained orange-brown "fake tan" skin after a few days of use, often in the creases of the hands or around the nail bed.
So why does Vitamin-C 'fake tan'?
Well the simple answer is - it turns into Erythrulose, a chemical often used to fake tan alongside the more commonly found dihydroxyacetone or DHA. Erythrulose gives that slightly redder, slower to appear, longer duration tan you get from brands like St Tropez and Dove and is the only ingredient in Deciem’s Hand Chemistry Glow Oil and Hylamide Glow Radiance Booster.
The less simple answer for those (like us) who want a bit more science is - the presence of sunlight, oxygen and moisture on our skin oxidises the Vitamin C (ascorbic acid) to Dehydroascorbic acid, which has an orange-brown colour.
This chemical process can be seen any time a cut fruit is left open to the air. Freshly cut apples have a strong yellow colour due to their high vitamin C content but turn brown when left out for several hours at room temperature. This browning is due to oxidation of the vitamin C and the colour change is due to this chemical reaction occurring. Once oxidised, vitamin C is no longer an active vitamin, meaning the vitamin C content of a fresh cut lemon is much higher than the vitamin C content of a browned lemon.
This process happens continually with Vitamin C, even within a product.
So why aren't all vitamin C skincare products orange-brown?
Well, this reaction is reversible so a product with the right antioxidants (vitamin E) in the formula will keep the process in check for the duration of the shelf life.
Without antioxidants however dehydroascorbic acid decomposes irreversibly into 2,3-diketogulonic acid and then erythrulose. Erythrulose reacts with the proteins in the top 'dead' layer of your skin to produce brown compounds called melanoidins which bind onto your dead skin cells until sheded off. This reaction also happens when meat and bread crusts turn brown with heat.
As our hands have a thicker layer of dead cells these are more likely to have noticeable stains than our face. Also our nail beds, and the creases in our hands, are more likely to pool serum for longer which means more erythrulose to react and more chance of orange oompa loompa hands.
So how can we avoid being stained by vitamin-C?
Wear gloves or moisturise your hands (and perhaps even apply a barrier cream to your nails) before using a vitamin C serum to act as a barrier.
Wash your hands with soap immediately after applying a vitamin C serum. DHA tan removal wipes are unlikely to help as it's a different compound.
Apply serums at night to avoid that oxidising sunlight.
Do not 'spot apply' serums. Spread them evenly over your face. This way any differences in skin colour will be less noticeable.
Don't rush applying your next product after using vitamin C to avoid streaking (Reddit users seem almost unanimously to recommend half an hour) but (and I know this is a contradiction) don't wait too long to apply oils and creams on top to protect the vitamin C from the air.
Buy smart and look at those ingredient listings: Ascorbic acid is the most unstable form of vitamin C and oxidises very easily. Other forms of Vitamin C are less likely to oxidise as quickly (although they may not work as effectively). Try to look for serum ingredients such as tetrahexyldecyl ascorbate, sodium ascorbyl phosphate, ascorbyl tetraisopalmitate and magnesium ascorbyl phosphate. Also, look for serums which have an antioxidant-rich formulation such as vitamin C with vitamin E or ferulic acid. These formulations will oxidise slower and give you more time to wash off/cover over the serum.