**Disclaimer: These views represent my experience with these products after using them consistently for months. My skin is acne-prone, combination and sometimes reactive, please keep in mind that may have a very different experience. My main suggestion is just to try to find a vitamin C serum that works for you. For a lot of people, that means a serum that has a derivative of L-ascorbic acid, so those are another great option. These are just my personal observations and experiences.**

*This post contains some affiliate links.

Why Do I Use a Vitamin C Serum?

Almost every morning I use a Vitamin C serum to helps protect against environmental damage and help prevent premature signs of aging. In addition to providing antioxidant protection, Vitamin C can also boost collagen production and help fade hyperpigmentation.  I definitely consider it a skincare staple. But all of these benefits don’t happen overnight, so I really believe that with Vitamin C (and most active ingredients) consistency and patience is key. 

Background of How I Tested Products

At the start of 2017 I started using Paula’s Choice Resist C15 and loved it. I went through two bottles and then I became curious how other vitamin C serums would perform (I am guilty of the “grass is always greener” mentality). Timeless reached out to me and asked if I wanted to try their serum, and I immediately said yes. I started using Timeless and about 2.5 weeks later a friend of mine on IG (@refresh_byhilary) sent me the Skinceuticals CE Ferulic serum (her friend mail blew me away with her generosity!). So at that point I started a split-face comparison where I always applied Skinceuticals on one side of my face and Timeless on the other. I did that consistently for 2 months. (Note: It was hard to split my nose up so there was a lot of overlap on my nose–just keep that in mind when evaluating the before and after photos. ALSO, keep in mind Skinceuticals had 2.5 less weeks on my face than Timeless).

Overall thoughts on each

Timeless Vitamin https://amzn.to/3J9YIfBC Serum

• $25 for 1 oz

I enjoyed using this serum (which was gifted by the brand). It had barely any smell, applied nicely and it didn’t contribute to excess oil on my skin. For the first month, I didn’t experience any irritation or dryness despite its low pH.  After about a month, I started to notice little jagged crystals sometimes made their way on my skin, and that is when I saw that crystals were forming around the opening of the product (I’m not entirely sure if there were any in the actual product or if they transferred to the dropper when I was applying it). When that happened it wasn’t pleasant but it also wasn’t a deal breaker, I just had to be sure to constantly wipe the top of the bottle to remove them before using it. However, I did start to wonder whether that was indicating the serum was oxidizing, even though the color wasn’t changing. (More on that below).  I also noticed that the side that I applied the Timeless serum was starting to become slightly more sensitive to wash cloths and acids, so that made me start to think that the low pH of the serum might be causing some sensitivity. Nonetheless, I did see improvement in pigmentation (at an almost equal amount as the Skinceuticals side).

Bottom Line: This is an affordable serum, and if it works for your skin, then it is an excellent option to get consistent antioxidant protection in short chunks of time. Because this has the shortest shelf life of the three (in terms of what the company states in terms of efficacy), this is a great option for people that can commit to using it on a consistent basis, because it really needs to be used up within 3 months of opening. The company says it expires 3 months from date of purchase… not after opening. So keep that in mind. It also worried me that it didn’t have an additional pH balancer to help keep the pH stable (which can also have an impact on overall efficacy). But that isn’t to say it isn’t an effective serum in the short term. I think that it works to address pigmentation and has an ideal concentration of Vitamin C, E, and Ferulic Acid. But given the low pH and issues I had with crystallization, I’m not sure this is the serum for me. I am currently testing another affordable L-AA serum by Maelove that has a higher pH (3.2) and includes a pH balancer, among other beneficial skin soothing ingredients. So that may be worth checking out if this one didn’t work for you.

Will I purchase the Timeless now that mine is gone? No.

Skinceuticals CE Ferulic

• $165 for 1 oz

The first thing that struck me about this serum was that it had the most potent “hotdog water” smell. Once I got past that, I liked how it applied and absorbed into the skin. I never experienced any irritation or stinging, and the bottle never formed crystals. It reminded me A LOT of the Paula’s Choice Resist C15 that I had used in the past (and loved). When I looked in the mirror, the Skinceuticals’ side of my face didn’t immediately seem brighter or with less pigmentation, but just before the 2 month mark I started to feel like the Skinceuticals’ side was looking brighter, Then, when I looked at the before and after photos I could see the breaking up and lightening of dark spots and fading of freckles was a bit more noticeable on the Skinceuticals’ side. And, remember that Skinceuticals had 2.5 fewer weeks on my face, so I think that showcases its efficacy as it seemed to have slightly better results. Let’s put it this way… If I had a big event (like a wedding or class reunion) coming up, I would consider purchasing this. But if a slow and steady approach works for you, I think with consistent use of either the Timeless or Paula’s Choice, you may find similar results. BUT what makes Skinceuticals so appealing to me is that it has so much research behind it. That matters to me when I am trusting that a product is really providing the full antioxidant protection I am hoping it provides–especially because it isn’t easy to have a before and after photo that can capture that.

Bottom Line: If this and Paula’s Choice Resist C15 were the same price, I would choose Skinceuticals because they have done efficacy and stability testing. But since the Paula’s Choice formula is so close to the overall formulation and effects, the products just seem far too similar to the Paula’s Choice Resist C15 for me to justify the cost difference.

Would I purchase this? Only if I had a big event coming up and I could find a coupon code that worked on it. Otherwise, I would rather the slow and steady approach with Paula’s Choice.

Paula’s Choice Resist C15 Super Booster

• $49 for 0.65 oz

I have purchased this serum twice now. I love how it comes in a smaller bottle (.067 oz) because that means I use it up right about the time that it is starting to oxidize and I never feel like I am wasting product. It absorbs nicely and never irritated my skin or led to any breakouts. If anything, it actually helped clear up my skin when I had active breakouts (Note: there are other that always break out from L-ascorbic acid, or even Vitamin E, so you may not have the same experience). I like how the dropper has a seal to try to help keep out air, and I loved how my skin looked with consistent use. I will say that I didn’t start to really see an improvement in pigmentation until I started to use it 5 days a week (initially I was using it 3 days a week). So now for all Vitamin C serums I aim for 5-7 days a week.

Bottom line: This is my favorite serum. It works for me and I love it. However, I always wait for a coupon code before buying it to save some additional money (for example, there are often 20% off deals on Paulaschoice.com or dermstore.com. It is even better when you combine those sales with ebates cash back).

• Sidenote: I used to think ebates was sketchy because I didn’t understand how it worked, so I avoided it. But once I read more about it, I was sold. If you do online shopping, you really should join. If you can remember to shop through the ebates site (or download the nifty plug-in that tells you how much cash back you can get on each website as well as what coupon codes are available) you can make a decent amount of money back. One immediate thing that I learned was that you don’t get access to the cash back immediately. Instead, they send out period checks every couple of months…but it is kind of nice because it will add up all those little cash back amounts up and in 3 months it can really add up! If you haven’t joined, here is my invite link that will get you get a $10 bonus credit or $10 gift card when you make a qualifying purchase of $25 or more through the ebates site (disclosure: I also get $5 if that happens). No pressure to use that link, so feel free to search the web and use someone else’s referral link, I just think you should definitely sign up! 

Will I repurchase? YES

How Do the Serums Compare?

How long will it remain stable? 

• Statement from Skinceuticals: “L-ascorbic acid may discolor with time, but oxidation is minimal and the formulation is proven to remain effective. All SkinCeuticals antioxidant formulations have been tested in final packaging and have been confirmed to remain stable and effective for 36 months, and up to 6 months after opening.”
  • Skinceuticals has undergone stability testing to show that their serum is at least 88% as potent even after a year of storage and when the color has gotten darker yellow. (Click here for more info). This may not matter to everyone, but knowing that their particular formula has been tested for efficacy and stability is a major bonus for me.
• Statement from Timeless: “Expires 3 months from date of purchase, can be extended with refrigeration storage.”
• Paula’s Choice: Paula’s Choice bottle lists a 3 month expiration date after opening.
  • NOTE: I just finished my 3rd bottle and when I was using it 7 days a week on face and chest the bottle lasted me exactly 3 months.

Ingredients & Overall Formula

[UPDATE: When Paula’s choice updated their packaging, they also updated their formula. See Paula’s Choice website for updated ingredient list]

All three products have the three main ingredients that I am looking for: at least 10% L-AA (with Timeless having the highest concentration), Ferulic Acid and Vitamin E. Check, Check, Check.

But Paula’s Choice and Skinceuticals both have some additional moisturizing ingredients. For one, I like that they both include glycerin, which is a great humectant.  All three have sodium hyaluronate, but it is higher up on the list for Paula’s Choice.  Paula’s Choice also has the inclusion of Acetyl Octapeptide-3, which is supposed to be similar to Argireline in that it is claimed to help reduce lines around forehead and eyes by impacting the muscle contraction process. I’m not entirely sure I buy that (and I didn’t find any studies to support it), but  having it as an additional ingredient certainly can’t hurt.

One thing to consider about the Timeless formula is that it has a really low pH (2.4) that may cause stinging and irritation for some people. I didn’t personally experience any immediate irritation, but I did have some sensitivity form over time. Also, I had my dad use it and he had a reaction from it (where his skin under his eyes turned bright red and was sensitive to the touch for almost two days). Some people won’t experience any irritation, but this is just something to keep in mind if you have sensitive skin or a compromised skin barrier.\

Paula’s Choice and Skinceuticals also get bonus points for including an additional pH balancer to help set the pH of the formulation to be just right (which can increase the concentration of the active ingredient and its benefits, Samuels, 2010).

All in all, I think the Paula’s Choice ingredient list and formula is a closer match to Skinceuticals than the Timeless one.  

Serum Color and Subsequent Oxidation

The Skinceuticals serum started out a pale yellow, whereas the Timeless started out clear. I did not notice any color change in the two months that I used these products (or in the month and a half that followed).  (At the end of this blog post I will include a picture to show what a fully oxidized vitamin C serum looks like so that you can get an idea of what a completely oxidized vitamin C looks).

• Based on color alone, Timeless is the clearest serum. But I am not entirely sure that just because it is clear that that means that it hasn’t oxidized. One reason for this is that my Timeless bottle formed crystals around the opening and if I wasn’t careful to wipe those off every time, I rubbed crystals on my face (which hurt). So even though the serum didn’t change color over time, it did crystallize, which I believe is a sign of oxidation.

  

• In terms of the starting color of each serum, This is an interesting blog post to read on this topic.   That author of that blog notes that a lack of tint does not guarantee that the product is free from oxidation because the early oxidation stages are colorless. That blog post also notes that both Ferulic acid and Vitamin E have a yellow/orange tint, so some pale color seems normal. BUT that doesn’t mean that I don’t always check for signs of oxidation because oxidized vitamin C is ineffective at best and damaging at worst.
• In the past, when I used Paula’s Choice Resist C15, it started to turn a slightly darker yellow around 3 months. When I kept it in the fridge it oxidized even slower (check out this IG post). So now I am a big proponent of keeping L-ascorbic acid serums in the fridge (or at least in a cold dark place) if possible.
  • I will note that I stopped keeping both the Timeless and Skinceuticals serums in the fridge after month 2 and neither have changed color (it is almost month 4, and both are almost empty). 
  • UPDATE!! Now that Paula’s Choice has updated their packaging to be completely opaque, I noticed an improvement in the amount of oxidation at 3 mths. (I just finished my 3rd bottle.) Also, I didn’t keep my 3rd bottle in the fridge, so that is even more promising.

Packaging

All products use dark glass to block out light and all three use a dropper. [UPDATE!! Now Paula’s Choice uses completely opaque packaging]. One difference is that Paula’s Choice has a design feature to try to keep air out. (This is where the airtight, pump packaging of the Drunk Elephant C Firma really shines). I prefer Paula’s Choice over the other two products because it has a smaller size bottle (0.67 oz instead of 1 oz) so when I apply it to my face and chest (and sometimes hands) I am usually almost finished with it right around 4 months mark. That makes me happy because I have never had to throw out the bottle with any oxidized serum left over.

Fading of Spots

As mentioned above, I think both serums helped to reduce freckles and dark spots. I personally think the Skinceuticals side did better at breaking up some dark spots on forehead (above eyebrow) and under my eyes. I tried really hard to match up the lighting from the before and after photos, but it was tricky. When I look in the mirror, the reduction in freckles above my eyebrow and under my eye looks more pronounced on the Skinceuticals side. Considering it had 2.5 less weeks to work its magic, I think that is a pretty good sign that you do get what you pay for. However, the Timeless definitely still worked to reduce pigmentation! (Yay!)

• Sidenote: I never really realized I had freckles on my eyelids before taking these pictures… #redheadproblems

**An important reminder when looking at these pics is that Vitamin C does a lot more than help with pigmentation. But the collagen-building effects of vitamin C can take up to a year to become visible, and it’s not really easy to know if something is providing great antioxidant protection (other than your skin not getting worse over time). So hyperpigmentation is just one piece of the puzzle.**

Consistency & Absorption

I think they all have a similar consistency and absorb equally well. When I was doing the split face comparison I couldn’t tell a difference between how they felt once I applied the Timeless and Skinceuticals on my skin.

Smell

Not a key criteria for me in terms of whether I like a product, especially since these are FAR from the worst smelling products I own (a fact my husband will gladly attest to and complain about), but if you can’t stand the hotdog smell of Skinceuticals, Timeless definitely has a much fainter smell. In terms of hotdog water smell I think Skinceuticals is the strongest, then Paula’s Choice, then Timeless. Luckily, the smell doesn’t linger on these, especially once you put another product on top.

Cruelty free

Both Timeless and Paula’s Choice are certified cruelty-free, but I couldn’t find any information on a cruelty free designation regarding Skinceuticals, so I am assuming they are not cruelty-free.

Other Vitamin C Serums I am Currently Trying…..

And because I am now addicted to comparing Vitamin C serums, you shouldn’t be surprised that I am already testing two new serums. I am currently testing a new affordable (~$28) Vitamin C by Maelove that doesn’t have such a low pH as Timeline (it is at 3.2 according to my meter), it has a pH balancer, has 15% LAA and has Ferulic Acid and Vit E (although the company said they couldn’t disclose what percentage those were at), and has other ingredients like aloe, grape seed extract and a few others to help with redness and signs of aging.

• UPDATE!! I finished my Maelove bottle and wrote up a review that you can find here

On the higher end, I am also testing Biopelle XCP Brightening Serum ($120 for 1 oz) with 10% L-AA, 2% phytic Acid (which has been an ingredient I continue to be impressed with!), and grape seed and green tea extract. So more to come!

• UPDATE!! I wasn’t able to test this properly because I foolishly opened it before I started testing the other products and I ended up having to throw this out because it had oxidized too much (not the products fault, I had it open long past its expiration date)

Like I said, I plan to repurchase the Paula’s Choice, so I am sure there will be another Vitamin C split face comparison in my future. 🙂 And because I often get asked this, I have only tried a sample of Drunk Elephant C-Firma day Serum ($80 for 1 oz), so I can’t give a true assessment on how that compares to these three serums other than to assess its consistency and feel on the skin (which I liked). And I can say that it has the best airtight packaging by far. I also like that it has a host of brightening ingredients in addition to the LAA, Ferulic Acid, and Vitamin E. I’m sure I will end up buying and trying that one in the future as well!

GENERAL TIPS

1. Since these serums are water-thin, I like to drop them directly on my face. I will apply one drop on my forehead and rub it in, and then apply a drop on one cheek and rub it in and then do the other cheek. I found that I wasted less product this way.
2. Don’t forget about your chest and hands when applying vitamin C. Having a serum that is affordable may make you more likely to be generous with your application, and that is a good thing.
3. Pick a serum that fits your budget and lifestyle. You don’t need to spend hundreds of dollars to reap the benefits of a vitamin C serum. I think the most important thing is to use it consistently, and check for signs of irritation. If L-Ascorbic Acid doesn’t work for you, be sure to check out some serums with L-AA derivatives. But your skin will thank you for applying a daily antioxidant. 🙂
   1. Sunday Riley CEO Rapid Flash Brightening uses a Vitamin C derivative and You.Skincare offers a serum with a blend of Vitamin C derivatives, just to name two products.
4. Don’t stock up on Vitamin C serums that use L-AA. Buy it and use it immediately. If you want to see a picture of a truly oxidized serum, see below.

Other Blog Posts on Vitamin C 

• If you are curious about The Ordinary’s range of vitamin C products check out these blog posts and videos
  • Amazingly comprehensive post by Detail Oriented Beauty
  • Video that not only covers Vitamin C in general, but two products in particular by Renee (aka Gothamista)
  • Review of two of Deciem’s Vit C products ( ascorbyl tetraisopalmitate and the vitamin c suspension) by Michelle of thebeautyendeavor.com
  • Overview of Vitamin C serums by Deciem
• For reviews on Drunk Elephant C Firma check these out:
  • Another video by Gothamista
  • A great post by Effie of infatuatedbybeauty.com
• And to round it out, here is a great Vitamin C myth-busting post by Michelle of labmuffin.com