Vitamin C is one of the few skincare ingredients with a ton of independent research to back up its properties, like its brightening and anti-wrinkle benefits. Those of you who are vitamin C enthusiasts may have noticed that with some vitamin C serums, you end up with slightly stained orange-brown skin after a few days of use – sort of like fake tan. I’ve often wondered why but didn’t really dig into it past a quick Google search (which found nothing), so I just put it off as a weird side effect of vitamin C oxidising.
But recently, I came across a diagram in a peer-reviewed paper on a completely different topic that accidentally told me exactly why vitamin C does this: ascorbic acid eventually oxidises to erythrulose!
As most of you may know, vitamin C in the form of ascorbic acid oxidises easily to dehydroascorbic acid, which has an orange-brown colour. It does this when it’s stored in water, as well as on your skin. Oxygen and light exposure will speed up the oxidation reaction. This reaction is reversible, so you can get back the ascorbic acid if you have the right antioxidants in the formula.
However, dehydroascorbic acid also decomposes, and it does it irreversibly. It turns into a number of things, but for our purposes here, we only care about the fact it turns into 2,3-diketogulonic acid, which then turns into erythrulose, according to the reactions I’ve drawn below:
Erythrulose is an ingredient in fake tans, and is often included alongside the more commonly found dihydroxyacetone or DHA. These ingredients react with proteins in the dead stratum corneum layer of your skin to produce brown compounds called melanoidins that stay on your skin until the dead cells come off (after around a week). The reaction is a Maillard reaction, like the reactions that happen when meat and baked goods turn brown with heat.
Related post: The Science of How Fake Tan Works
Erythrulose is notable for giving a slightly redder tan than DHA that stains more slowly, less streakily and lasts longer. It’s included in tans from St Tropez, Bondi Sands, Jergens, Dove and Models Prefer that have DHA as the main ingredient. It’s also the sole ingredient in Deciem’s Hand Chemistry Glow Oil and Hylamide Glow Radiance Booster.
So that’s why vitamin C serums can stain – the ascorbic acid essentially turn into fake tan on your skin! Mystery solved.
How to Avoid Vitamin C Staining Your Skin
So now that we know why vitamin C serums can stain, how can we prevent this from happening? There are a few approaches:
Prevent oxidation
Preventing the vitamin C from oxidising is the obvious way of keeping the erythrulose down in the first place. You can use an antioxidant-rich formulation like vitamin C + vitamin E + ferulic acid (e.g. Timeless or Paula’s Choice). What I’ve found helpful with my low-tech, budget-friendly DIY vitamin C serum is to immediately use oils and creams on top to protect the vitamin C from the air. Using it at night, away from high energy sunlight, will also help.
Related post: Water-Based Vitamin C Serums
Use oxidation-resistant forms of vitamin C
Ascorbic acid is by far the most unstable form of vitamin C and oxidises very easily. While the other forms of vitamin C aren’t as researched and require your skin to take a few extra steps before working, they also won’t oxidise anywhere near as badly on your skin. Some of these oxidation-resistant vitamin C ingredients include:
- magnesium ascorbyl phosphate (e.g. from The Ordinary)
- sodium ascorbyl phosphate
- ascorbyl tetraisopalmitate (also known as tetraisopalmitoyl ascorbic acid or ATIP, e.g. again from The Ordinary, who seem to have every variation of vitamin C, and from Moogoo)
- tetrahexyldecyl ascorbate (THDA, e.g. from Sunday Riley, Medik8)
Related post: Oil-Based Vitamin C Serums
Wash your hands after applying vitamin C serums
Fake tan ingredients stain dead skin cells, and your hands tend to have a thicker stratum corneum. This means that sometimes your hands will turn brown even if your face doesn’t noticeably stain! To avoid stained hands, just wash them with soap immediately after applying the vitamin C serum.
Apply vitamin C serum evenly over face
Some of you might not mind the colour – it can actually give you a nice rosy glow! If that’s you, then apply the serum as evenly as possible and regularly exfoliate your face so the tan fades evenly. If you notice streaking, increase the waiting time between applying vitamin C serum and your next product (try half an hour as a starting point).
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What about The Ordinary’s Ascorbyl Glucoside solution? I mix this in the AM with their ferulic acid/resveratrol serum and a drop of hyaluronic acid…
It should be oxidation-resistant! 🙂
Very interesting post!
Is Erythrulose bad for skin? Does oxidation mean, that it accelerates ageing of the skin?
Nope! It isn’t bad for skin – it might increase free radicals while you’re in the sun by a tiny amount if it’s like DHA, but it’ll be insignificant.
Thanks so much for this post! I’ve been having this issue with the 23% Vitamin C from the Ordinary and I always have the impression that it makes my hands smell like self-tanner, now I know why! 🙂
I don’t really mind the staining too much (tbh I kind of like the smell), but what really makes me worry is: when the Vitamin C oxidizes on my skin, does it form free radicals there and possibly cause more harm than good and eventually really damages the skin?
There’s a low chance, but no one really knows – it seems that unstabilised Vit C serums still have good results in studies so overall it looks like it ends up being a net positive 🙂
i think as Michelle have mentioned, if you want to be extra careful about it you can mix it in with other antioxidants to keep the vitamin C stable. you’ll get extra benefits from it anyway
I never had that happen, at least not to a point where I did notice, but it certainly is interesting.
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I’ve only had it happen a couple of times to my fingertips!
Yes, I did notice the tint on my nail bed and cuticle area. I recently added an additional vitamin c. the old one never tinted. Now, one of the ones you mentioned was added and I have the tint. Glad to know why. Thank you.
Glad I could help solve that mystery! 🙂
I had this happen with Ole Henriksen Truth Serum, but it didn’t stain evenly – mostly around the “marionette lines”. None of the other Vit C serums have done it – so good to know what was happening, it kind of freaked me. I always smile when I see Maillard Reaction, I did my biochemistry paper on it some 33 years ago. Who would have thought we’d be using it for fake tans – lol- back in the day when it was fashionable to bake in the sun slathered with baby oil.
Haha I didn’t think I’d ever see the Maillard reaction again after a molecular gastronomy lecture I went to once… how wrong I was!
This is so interesting! I had no idea ! Such a great extensive blog post 🙂
Thank you! 🙂
Ha! I do not mind it at all.
I haven’t minded it so far, but I’m also a bit irregular with my vitamin C usage -_-
Sorry this is off topic but can I use two different types of vitamin c( indeedlabs vitc24 and TO ascorbyl glucosidr)?
Should be fine 🙂
Hi, Michelle!
I had a quick nail polish question for Google at about a quarter to midnight, which led me to your blog. It’s now nearly four in the morning, and I’m forcing myself to stop reading and go to bed.
You’ve completely hooked this lipstick-obsessed nerd’s heart and mind! Thank you!
Hahaha that’s fantastic! Thank you! 😀
I’ve noticed my skin turning brownish-red and my palms being a bit more tanned. i thought it was odd, but I’ve realized it could probably be the vitamin C oxidising! I’ve noticed this on Paula Begoun’s palms as well, and she likes to use her vitamin C. i don’t know the mechanisms to it but thanks to you, now I know why! you’re brilliant and you’ve helped everyone a lot with your bite sized research! thank you Michelle.
Hi Michelle,
What do you think of a serum with 12% LAA and 88% butylene glycol (e.g. CSI serum)?
Is this a stable formula?
Thank you
Anna
Hey Michelle! Do darker skin tones (I’m a dark skin African American ) have to worry about this staining? I certainly haven’t noticed any tanning of my skin, but I have noticed that it’s brighter! I was just wondering if it was different for people with my type of skin. Thanks (:
It probably won’t be very noticeable on your skin 🙂
used my usual skincare incorporating vitamin c (c21.5 by wishtrend) and vitamin e, and a zinc sunscreen (no makeup) and when removing with makeup remover i noticed the gunk i was wiping off was yellowy.
i’m assuming this means it oxidized on my skin? (it’s kept in the fridge usually and the solution is not yellow)
PHEW! Great article! I just started using a vit. c serum and was disturbed by this phenomenon. I was mostly concerned I had a bad batch, or the brand was bad or poorly made. (one of the many reasonable priced brands on amazon similar to Timeless). I was wondering if the “glow” they claim the serum will cause was a scam and it was just a tanner, masking your imperfections, making you think your skin is actually improving. I contacted the company but no response. I wonder if even they know of this explanation.
I stumbled onto your blog through your Vitamin C posts while debating the relative merits of making my own l-ascorbic serum, Drunk Elephant’s C-Firma, or venturing into tetrahexyldecyl ascorbate with Sunday Riley’s C.E.O serum. (I have Sephora gift cards and a sale that starts tomorrow, creating an odd scenario in which purchasing ingredients is actually not as cost effective as using “free money”.)
I am just a bit stymied as to what your intended meaning is by striking through “Sunday Riley” in the product links. Do you feel that her version is less effective than Medic8? Any clarification would be greatly appreciated.
Thanks in advance for any response.
I’m planning to do a post comparing different types of vitamin C soon 🙂
The strike-through just means that my link is broken – I’ve just disabled that CSS!
This caused me to give up on Vitamin C serums.
I like having light porcelain skin and do not think the fake tan looks good at all.
There are other ways to keep skin healthy from the sun and other elements (sunblock, maybe B3 etc. etc.). Also light skin allows me to see the condition of my skin better, otherwise I could miss redness and other things.
My skin has turned a darker brown due to using oxidated vitamin c serum. I ujust wanteda to know how i can remove the stain from my face
Hi Michelle! I can’t tell you how much I appreciate your blog, and particularly this entry as it has solved a major mystery for me. As soon as I receive all the ingredients, I’m going to begin making a more stable DIY l-ascorbic acid based vitamin C serum for myself. In the meantime, I have a jar of The Ordinary L-Ascorbic Acid Powder, and have been mixing it with Hada Labo Premium on a daily basis to use as a serum. It’s been working great for brightening my face, but was turning my nails and fingertips the most horrid orangish-brown that looked like I was a 3-pack a day smoker! I can really scrub my hands after applying the serum, but the only thing that gets the stains off of my nails is to stop using it for a few days. I’m going to try your tip of slapping some oil on my nails after washing my hands, which will be good for my nails anyway! Thank you so much! 🌸💕
Hi Michelle,
I came to this article by way of the Well And Good blog (and also, I just started subscribing to your newsletter) and I wonder whether this could be an issue with The Ordinary Vitamin C Suspension 23%, which claims to be stable.
I haven’t noticed any staining on my fingers and I am Afro-Caribbean but I am using it as part of an anti-hyperpigmentation regimen (dark spots are a persistent problem for me), so I wonder whether I might be working against my skin’s own benefit.
What do you think?
I think it’s probably an issue (although I haven’t tried that particular product) – I haven’t tried any ascorbic acid product that doesn’t stain. The staining doesn’t contribute to hyperpigmentation, luckily!
Is there anyway to avoid staining from shirt?
as i use the ordinary vit c 23% + Ha, and it does stain my shirt badly.
use detergent cannot remove it thorougly.
Hi Michelle,
I’m new to your blog and wanted to tell you how happy I am that I found it! I start reading one post and I end up down the beautiful rabbit hole from clicking all the informative links in each post.
This post FINALLY explains why it looks like I have a perpetual tan on my face even though I slather SPF 50 zinc oxide based sunscreen daily on my face on top of my Timeless Fit C but have pale, pale skin on my neck (no Vit C just sunscreen)! I really hate the effect since it looks like I have darker foundation on my face and not my neck when I don’t have any on at all! If you have any other suggestions to lessen this sunless tanner effect, I would really appreciate it.
Do you use exfoliant? Exfoliating might help fade it faster! You could also switch to a different form of vitamin C.
Hi Michelle,
So happy to find your post when I was searching for Vitamin C forms. So does it mean ascorbyl tetraisopalmitate and tetrahexyldecyl ascorbate are different forms/molecules? Because The Ordinary Ascorbyl Tetraisopalmitate Solution 20% has Ascorbyl Tetraisopalmitate in its name but the ingredients listed only contain tetrahexyldecyl ascorbate which makes me think they are the same form. If they are different, then what are differences between them?
Thank you.
Mai.
Would you please consider doing a review on the Melanie Simon vitamin C? She claims it is incredibly stable and it is getting rave reviews and lots of publicity. Love everything you do! Xx