5 Skinceuticals Vitamin C Dupes Put to the Test!

First Posted on August 2, 2023 in:shop like a protop readsvitamin c

If you’re unfamiliar with the term “Vitamin C Dupe”, it’s a category of ascorbic acid serums that sprouted from the painful price point of the original ascorbic acid serum, Skinceuticals CE Ferulic.

As a result, a whole new category of ascorbic acid serums popped up on the market and these products come in all sorts of packaging, price points, and ascorbic acid percentages. For a while, we were holding out on looking at this category because it felt messy. Let’s just say, we knew how much of a challenge it can be to formulate and bottle this formula correctly that we just couldn’t speak well to whether or not these dupe brands were truly a good 1:1 replacement with the original.

So we decided to put a few of these formulas to the test to see if there were any tips we could provide in sussing out and finding the “better” dupe.

What Vitamin C Knowledge You Need Going Into this Test

The Vitamin C (L-ascorbic acid), Vitamin E, & Ferulic acid combination is what has been validated through decades of research spearheaded by Dr. Sheldon Pinnell. In their studies, they discovered a synergistic effect when using Vitamin C & Vitamin E, and the combination of the two provides antioxidant, free radical quenching benefits from both UVA & UVB exposure.

*def: synergistic effect - the sum benefit of combined actives is much more than the benefits of each of the individual actives. Ie. 1+1 doesn’t equal 2, it’s >2. 

However, like many good actives, this combination is not the most stable. Ascorbic acid is not stable in water and further dies a rapid death with exposure to light and oxygen. Additionally, one of the byproducts from this degradation is carbon dioxide which will cause gas to build up in the packaging. A lot of work has been done to help improve the stability of this formula but the general understanding is that once this product has been opened, it’s important to go through it and keep it stored in vampire settings: cool, dark, and sealed. 

What Vitamin C Serums We Put To the Test

We decided to test the top 5 ascorbic acid dupes that we’ve come across from our follower questions, recommendations, and general buzz. These candidates are: CosRX The Vitamin C23 Serum, Paula’s Choice C15 Super Booster, Dr. Brenner’s C Serum, Timeless 20% Vitamin C+E Ferulic Acid Serum, and Maelove’s Glow Maker.  

For fun, we decided to also test 1 anhydrous ascorbic acid serum just as a comparison: The Ordinary’s 8% Ascorbic Acid + 2% alpha arbutin serum in propanediol (a popular solvent and molecular cousin to propylene glycol). In a non-aqueous base, the stability should be much better.

Finally, as an additional comparison, we created our own fresh concoction of CE Ferulic in the lab to compare degradation time.

How We Tested These Vitamin C Serums

As a QA/QC measure, all skincare products go through stability testing. One of the tests conducted is an accelerated stability test where the product essentially gets incubated in a heated oven for weeks at a time and it gives you an idea of how your product would sit on shelf in a 2-3 year timeline. For these selected serums, we’ll heat these products for just 3 weeks (stability tests are typically run for much longer) and observe for any formula changes weekly.

The Results of the 3 Week Accelerated Stability Study

Test Start! T=0

putting common CE ferulic dupes in the oven to test stability

You’ll see our lab-made batch all the way to the left. Initially, vitamin C serums are essentially completely clear. Paula’s Choice, and Timeless Skincare all started out with just a hint of color, while Dr. Brener and Maelove are pretty much clear. This spectrum of coloring is normal. Upon opening Paula’s Choice & CosRx’s products, there was a subtle release of gas build up in the bottles right from the start. We should also note CosRx’s stronger yellow tint at initial.

After Week 1

putting common CE ferulic dupes in the oven to test stability


We see a yellow hue starting to come in more for all serums and you can smell the “hot dog water” scent more. This is pretty normal. Timeless has a funky darker globule that we’ll ignore. This is from product build up in the pump itself. Additionally, both Paula’s Choice and CosRx had gas build up in the bottle. Additionally, you can see that CosRx’s dropper visibly ballooned. We would raise an eyebrow at how quickly CosRx’s pipette ballooning occurred. 

After Week 2:

putting common CE ferulic dupes in the oven to test stability


This is where things start to get interesting. Most of these serums’s color didn’t change a lot except for Timeless. Only CosRx’s formula had gas build up and ballooned again. We also want to note the CosRx formula splattered in a way that almost seemed to not like itself and started to run away from each other. Interesting…

After Week 3:

putting common CE ferulic dupes in the oven to test stability


We’ve reached the end of the study! The yellow to brown tints are really starting to come in for most of these products. CosRX consistently ballooned and had gas build up again and more alarmingly, the formula seems to be separating.

Discussion of Results

Maelove Glow Maker / Dr. Brenner Vitamin C Serum / Paula’s Choice C15 Super Booster

 We would pass all three of these ascorbic acid serums. The progression of color, lack of exciting packaging development, and general smell development were all normal.

Timeless Skincare 20% Vitamin C + E Ferulic

 Despite this formula’s more rapid degradation and sputtering (where formula jets out when pumping), we would still pass this formula. We definitely don’t love the plastic pump packaging it came in. So we would recommend purchasing Timeless’s new Vitamin C serum that comes in a glass airless pump on their website vs. purchasing from Amazon which still uses the previous plastic airless pump packaging.

CosRX Vitamin C23 Serum

 Oof… sadly, this one had an accumulation of red flags. From consistent CO2 build up, really strong smell, and formula separation we would definitely avoid this formula. This formula contains a bunch of other actives, some more fussy than others, which in theory sounds great! However, ascorbic acid is fussy enough that the formula has seemed to morph into quite the three headed hydra of issues. 

The Ordinary’s Ascorbic Acid 8% Alpha Arbutin 2%

 As you can see, when ascorbic acid isn’t formulated in water, it does so much better! The Ordinary’s vitamin C serum actually remained quite clear through the entire experiment. However, using a serum that is 90% solvent can be irritating for some skin types. If you find yourself giving up on these water-based ones and you’d like to give this a try, definitely patch test!

How to Shop For Vitamin C Serum Dupes

  1. Price point matters…and it doesn’t matter: It’s definitely ok to use Skinceutical’s CE Ferulic. Those guys have been manufacturing this formula the longest and there’s a sense of insurance in the efficacy and your product experience. It’s also definitely ok to use the cheaper Vitamin C dupes as well - as long as they arrive in a relatively fresh state. 
  2. Support active ingredients out side of the original trio C, E, and Ferulic don’t matter all that much: Given that this is such a popular product to emulate, some brands go the route of creating their own one-up version with a whole slew of additional active ingredients. We’d say… that’s not necessary. In fact, too many fussy ingredients can potentially compromise vitamin C stability, defeating the purpose of the whole serum. We’d say those other ingredients shouldn’t be the determining factor
  3. Dropper Bottle or Airless? From the study, you can see that the quality of each of these can vary. That means there really isn’t one that’s better than the other here. Just be sure to diligently go through the product and store it the way it likes to be stored :)

Ultimately, the general rule of thumb is to pick an ascorbic acid serum with pH lower than 3.5, texture that you enjoy (some of these can get sticky), and consistently arrive to you in a fresh state.

What You Should Look Out For When Using Vitamin C Serums

Vitamin C Serum Shelf Life Stability Check List

We would consider all of these red flags. More than two red flags…it might be time to let that bad boy go:

  1. Gas build up: When you open this product, does it sound like you opened a semi-flat coke?
  2. Pipette Ballooning: Is your pipette bulb looking…too bulbous?
  3. Rapid color change: Feel free to use our test results as a guide. Anything from a clear to amber is fine. Anything darker or when the formula takes on multiple hues, it might be time to let it go.
  4. Smell Evolution: Smell evolution is part of the Vitamin C experience, but we’ve smelled some that just isn’t right. If your ham-smelling serum takes on a expired meat broth odor, it might actually be expired.
  5. Formula Separation: Ok if this happens, ignore the rest and just let it die a quick death. One way to notice something is off is if you see the formula start clinging to the dropper tip in weird ways, as if there are bit stuck to the sides of the glass. We wouldn’t completely write this off, but definitely a “beige” flag to keep monitoring.

Products Tested in this Post


1. Why do Vitamin C dupes exist?

The combination of CE Ferulic has decades of research supporting its benefits as a true antioxidant serum that quenches free radicals and minimizes UV erythema. It also has been shown to help with collagen production, prevent collagen degradation, and provide skin brightening effects.

2. Should I still buy Skinceuticals CE Ferulic?

Skinceutical’s CE Ferulic is the original patented formula. Price point aside, it’s definitely still a quality product other brands try to emulate. 

3. Should I buy a Vitamin C serum with more than the CE Ferulic?

Many formulas might throw in an additional active so it’s not such a blatant dupe. We wouldn’t factor this into our purchasing decision and definitely don’t recommend basing purchasing decisions on the amount of additional actives these serums come with. In fact, if it comes with a baker’s dozen additional actives, it might even be a red flag.

4. How do I know when to throw out my Vitamin C serum?

Look for multiple signs: rapid color change, intensity of color change (black coffee coloring), gas build up, and smell evolution. However if you find your formula doesn’t look uniform, seems to be separating, or there seems to be things floating in the formula we would immediately move on.



Vitamin C: The Antioxidant Powerhouse

Vitamin C serums is probably one of the most popular products with countless new launches every year. Their lasting popularity make a lot of sense! Simply put, Vitamin C (specifically ascorbic acid) is one of the most validated actives in the skincare world for its clinical benefits. It has been proven to prevent free radical damage, brighten hyperpigmentation, and even boost collagen production. But given vitamin C’s popularity, it’s only gotten MORE difficult to choose the best vitamin C se...

Read more