After being exposed to air (like when you open the bottle) Vitamin C will oxidize and change color. Typically serums start out as clear and can degrade to yellow, orange, and in extreme cases all the way down to muddy brown. L-ascorbic acid (aka Vitamin C) serums should last around 3-6 months before showing any signs of discoloration.
What color should Vitamin C Serum be?
Vitamin C is derived from oranges so it makes sense that it would turn yellow, right? In reality, Vitamin C dissolved in water is perfectly clear. An orange-tinted serum is actually not a good thing at all!
In a 2018 interview with image.ie dermatologist Dr. Rosemary Coleman said:
“Vitamin C has quite a complicated chemistry, and because it’s a water-soluble vitamin, it becomes very unstable in water solutions. Additionally, vitamin C doesn’t penetrate the skin easily, it degrades on exposure to oxygen, and it favors a pH around three, which is too acidic for human skin. Just because a company throws some vitamin C into their concoction doesn’t mean it is actually active,” says Dr. Coleman.
Vitamin C is a tricky ingredient to successfully bottle in serums due to its unstable nature but I have some tips and tricks to share on how to extend the shelf life of this finicky but well loved skincare product.
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Will using a discolored serum hurt my skin?
Throwing out a serum just because it slightly changed color is a painful thought. I’m an extremely thrifty gal so you’d be hard pressed to find me throwing a skincare product out unless it’s life or death. Using an orange-tinged serum won’t hurt your skin per se, but it could stain it! *gasp*
The color of your serum indicates how potent it is. For example, clear serum straight out of the box has 100% potency. Light yellow might be 80%, orange 60%, and if you really let it go and oxidize enough that it turns brown you might be looking at 50% potency. Each shade of oxidation can potentially be a 10% loss of potency! Just think of all that lost skincare real estate being taken up by useless serum.
This highly varies depending on the formulation and concentration of Vitamin C but this color change is a visual indicator that you are losing Vitamin C. When it changes color it is actually breaking down into different kinds of acids like dehydro-L-ascorbic acid and eventually diketogulonic acid. So the percentage of Vitamin C is actually dropping when you see a color change!
Why did my Vitamin C serum stain my skin?
This can happen because vitamin C degrades into erythrulose—a common ingredient in many self-tanners! A tan from erythrulose can last up to seven days and takes 24-48 hours to develop. You would have to use quite a bit of degraded Vitamin C serum to get significant discoloration but it can take quite a while to fade if you manage to get to that point. These degraded acids can also damage delicate skin.
You don’t have to toss a serum if it’s only slightly yellow but if it’s tipping into orange it’s time to trash it.
How Long Can Vitamin C Serum Last?
An unopened bottle can last up to three years but once that seal is popped the clock starts ticking! The lifespan of your serum is dependent on the formulation and if it includes ingredients that help stabilize Vitamin C like ferulic acid or Vitamin E. Typically you’re looking at around 3 months shelf life once the serum is opened. This timeframe can be shortened if the serum is exposed to sunlight, left in a warm spot, or is not closed properly and exposed to excess air.
How do I stop my serum from oxidizing?
There are some preventative steps you can take to delay your serum from degrading. Heat, oxygen, and light are the big baddies we need to shield our serums from. If you have to use a dropper make sure you are screwing the cap back on asap. Airless pumps nix most of that air exposure so I highly recommend them over the standard glass dropper bottles.
Vitamin C is one of the few skincare ingredients that actually benefit from refrigeration, so make sure to make some space in your nifty skincare fridge! I have a rambly breakdown on the pros and cons of skincare fridges here. If you haven’t yet reached that level of extra make sure you keep the serum in a cool cabinet drawer far away from your steamy bathroom. I’m a huge fan of lava-hot showers so I keep my serums under lock and key in an airtight cabinet.
Many serums will come in dark brown bottles due to Vitamin C being so unstable and photosensitive. But if you got unlucky and have a clear bottle, make sure this is kept in a drawer away from sunlight. You could also cover the glass with a sticker or tape, but I know I personally don’t want to mess up the manufacturer label in case I want to check something in the future.
Is a Vitamin C serum worth it?
Vitamin C is proven to improve skin elasticity, decrease wrinkles by stimulating collagen synthesis, boost the skin’s immune system, and repair damage caused by free radicals. But the dark side to all of these awesome benefits is Vitamin C’s wild instability which is the entire reason I’m writing this piece for you! So yes, it is worth it. But on the other hand, there are much easier ingredients to store that give the same benefits so it really boils down to personal preference and what you want to put up with.
Start by looking for L-ascorbic acid serums that also include ferulic acid and vitamin E, which will help stabilize the formula (plus they double its photoprotection!). You can also look for formulas made with ascorbyl glucoside, magnesium ascorbyl phosphate, and tetrahexyldecyl ascorbate.
I would rather have a combination serum that will last long enough for me to work through the entire bottle instead of a purely Vitamin C serum that will oxidize within 3 months of opening it. I don’t know about you but I’m constantly playing with new skincare products and can’t stick to one product cold turkey. It would be impossible for me to work through an entire bottle in such a short time frame. I highly recommend this Vitamin C & E serum by Yeouth, I got it from iHerb here.
Can I use Vitamin C serum every day?
Vitamin C is a great kind of serum for daily use. It’s gentle enough for any skin type and you can be used twice a day in your morning and nightly skincare routine. Make sure to seal your serum in with a good moisturizer before finishing off your skincare routine. I love combining Vitamin C with the Drunk Elephant Protini cream (you can check it out here). If you’re looking for a more budget-friendly moisturizer to pair up with your serum I highly recommend the Nature Republic Super Aqua Max Cream.
If you need help finding the right type of serum for your skin type check out my guide here!
Are you a fan of Vitamin C? If not, what’s your favorite skincare ingredient?
