ADVERTISEMENT INFO: SOME PRODUCTS MENTIONED IN THIS POST ARE PR (GIFTED) AND LINKS USED ARE AFFILIATE LINKS. I RECEIVED NO MONEY TO WRITE THE BLOGPOST. PLEASE READ DISCLAIMER
If you’ve ever felt frustrated by Vitamin C serums—either because they irritate your skin or because you’re unsure if they actually work, you’re not alone in that confusion. The skincare world keeps telling us that L-Ascorbic Acid is the gold standard. But what if your skin can’t tolerate it? Or what if the solution everyone recommends isn’t the right fit for you?
That’s exactly where Tetrahexyldecyl Ascorbate steps in. It’s the form of Vitamin C inside the Sunday Riley C.E.O. Serum and some people swear it’s just as effective, but much gentler.
I’ve been testing it to see whether this luxury serum lives up to the claims and whether it really is a better option for those of us with sensitive or maturing skin. In this review, I’ll break down exactly how this Vitamin C derivative works, what the science says, and—most importantly—whether it’s worth your money.
What the Sunday Riley CEO 15% Vitamin C Brightening Serum claims
CEO 15% Vitamin C Brightening Serum, is targeted to quickly fight the look of dullness, dark spots, and discolorations at the source, while diminishing the signs of premature aging. Skin looks firmer and plumper, as youthful skin bounce and even-tone are restored.
Facts about the Sunday Riley CEO 15% Vitamin C Brightening Serum
Prize and size
There are two different sizes available: 30 ml for 86,95 € or 50 ml for 131,95 €, out of which the latter is obviously better value for money (get them here). Both are incredibly expensive though.
It shouldn’t matter, but the packaging looks that part – a glass bottle in orange with golden flecks and a pump. The pump works very well and delivers exactly the right amount needed for my face and neck.
Texture and smell
Now there are watery serums and creamier ones, and this one belongs in the latter category. It feels like a lotion when applied, is white (no golden specks in here, that is strictly limited to the bottle) and has a beautiful, subtle citrussy scent.
How to use the Sunday Riley CEO 15% Vitamin C Brightening Serum
According to the website you should use two pumps morning and night for your face, which I think is a lot. Due to the great spreadability one pump is enough to cover my face and take it down on my neck – maybe I just have a small head, but I think two pumps just for the face would be too much. And while you can use Vitamin C twice a day, I usually stick to once a day in the mornings. The reasoning behind using it twice a day is that during the day, it will be used up to combat free radicals, while at night it could work on brightening hyperpigmentation and increasing collagen synthesis. There is surely truth to that, but I have other things in my eveening routine and don’t want to use a gazillion steps, so I trust that there will be something left for other things even when applied in the mornings. (More info: What skincare can you pair safely with Vitamin C?)
Given that it doesn’t use L-Ascorbic Acid, but Tetrahexyldecyl Ascorbate, using it twice a day and even alongside other actives would work well, as there is a lower irritation potential.
The difference between L-Ascorbic Acid and Tetrahexyldecyl Ascorbate
Let’s talk about something that often confuses people: the difference between L-Ascorbic Acid and Tetrahexyldecyl Ascorbate.
L-Ascorbic Acid is widely recognized as the gold standard when it comes to Vitamin C in skincare. Maybe you’ve tried it yourself and experienced that uncomfortable stinging or redness. Or maybe you’ve heard it’s notoriously unstable, degrading quickly after opening. That’s where Tetrahexyldecyl Ascorbate comes in. It’s an oil-soluble form of Vitamin C, which allows it to penetrate the skin’s lipid barrier more easily. It’s also much more stable than L-Ascorbic Acid and doesn’t require a low pH to remain effective—this is a big deal because it’s often the low pH (around 3.5) of L-Ascorbic Acid formulas that irritates sensitive skin, not necessarily the Vitamin C itself. (More info: The different types of Vitamin C exlained)
Sounds amazing, right? But here’s the catch: While early studies show that Tetrahexyldecyl Ascorbate can convert to active Vitamin C within the skin and help with hyperpigmentation and signs of aging, the available data is limited. The sample sizes are small, and most studies have some limitations.
In contrast, L-Ascorbic Acid has decades of solid research proving its effectiveness for brightening, collagen production, and antioxidant protection.
My take? I personally prefer L-Ascorbic Acid because I tolerate it well and appreciate the stronger evidence. But if you struggle with irritation or dislike the idea of using low pH products, Tetrahexyldecyl Ascorbate is absolutely worth trying. It’s a great way to get some of the benefits of Vitamin C without the downside of sensitivity.
Ingredients of the Sunday Riley CEO 15% Vitamin C Brightening Serum
aox|sb, Squalane sii|emo 0 1, Polyglyceryl-6 Distearate emu, PEG-8 Beeswax emu, Limonene 
perf|solv, Citrus Sinensis (Sweet Orange) Oil perf, Citrus Tangerina Peel Oil, Glycine Soja Sterols emo, PPG-12/Smdi Copolymer, Sodium Phytate chel, Tocopherol aox 0–3 0–3, Phenoxyethanol pres, Acetamidoethoxyethanol h, Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer vc, Sodium Acrylate/Sodium Acryloyldimethyl Taurate Copolymer vc, Jojoba Esters so|emo|h, Glycolic Acid 
exf|buff, Caprylyl Glycol h|emo, Cetyl Alcohol emo|vc 2 2, Polyglyceryl-3 Beeswax emu, Chlorphenesin pres|amic, Glycerin sii|h 0 0, Polysorbate 60 emu|surf, Sorbitan Isostearate emu 0 1–2, Saccharide Isomerate h, Linalool perfHover the mouse over an ingredient for short explanation. Read more on INCIDecoder.
Now what else is there in the formula? The first thing you I noticed is that Squalane is quite high up on the ingredient list, which explains the lotion like texture. There are also other moisturizing and hydrating components like Glycerin, Acetamidoethoxyethanol and sugars, and in fact I feel like if your skin is oily, this might well work as last step in your routine in summer without the need for an additional moisturizer.
Then you have Vitamin E as additional antioxidant and then, kind of counteracting the benefits of their Vitamin C choice for sensitive skin, a whole lot of fragrant essential oils from the citrus family alongside Limonene and Linalool. Now obviously what your skin reacts to will depend on your sensitivities, but fragrant essential oils are common culprits in those that react, which is why I wouldn’t wholeheartedly support the recommendation of this product “for sensitive skin”. (More info: Is fragrance in your skincare products dangerous?)
More info: How to read the skincare ingredient list
Does it live up to its claims?
Yes.
It at least has the means to do everything it claims, which is what Vitamin C serums in general claim: to brighten, to firm and to protect from further damage.
How does it compare to…
Geek and Gorgeous C-Glow Serum
This is my favorite Vitamin C Serum and the one I compare all the others I test against. The main difference here is that Geek and Gorgeous uses L-Ascorbic Acid and subsequently has a low pH. I tolerate it well and would encourage everyone to see if they can use it as I have heard about many that struggled with other Vitamin C serums, but got along well with this one.
You can read my full review of the Geek and Gorgeous C-Glow Serum here.
Medik8 C-Tetra Luxe Vitamin C Serum
The version from Medik8 uses Tetrahexyldecyl Ascorbate as well, at a concentration of 14%. It is pretty similar in price and shares the addition of fragrant essential oils, which could make it troublesome for those with sensitivities. It is quite different in texture though, leaning more on the oily side rather than feeling like a lotion, so depending on yout personal preference, one or the other might suit you better.
You can read my full review of the Medik8 C-Tetra Luxe Vitamin C Serum here.
Biossance Squalane + Vitamin C Rose Oil
The last option I want to share isn’t a serum, but a facial oil, meant to be used as last step in your routine. It is part of the Biossance Squalane + series and contains Tetrahexyldecly Ascorbate alongside Rose Oil and Squalane. Similar to the version from Medik8 it is an oil rather than a lotion, but a lightweight one that didn’t feel oily or suffocating on my skin. I have no information about the concentration of Tetrahexyldecyl Ascorbate used.
You can read my full review of the Biossance Squalane + Vitamin C Rose Oil here.
Would I repurchase and which skin types do I recommend it to?
The Sunday Riley C.E.O. Serum has a beautiful texture and a lovely scent—it’s one of those products that makes your skincare routine feel a little more luxurious. I can absolutely see it being a great fit for those with maturing skin looking for a gentler Vitamin C option or for anyone who struggles with irritation from L-Ascorbic Acid but still wants to enjoy antioxidant benefits – if the price point is within your range, that is. However, I do recommend patch testing first, especially if you’re prone to reactions from fragrant essential oils. Due to the Squalane and other hydrating ingredients was able to use it as last step in my routine without feeling the need to use a separate moisturizer on top.
Shop Sunday Riley here
Don’t forget to check out the Discount Code Page on top if you want to save some money on your next skincare purchase, or click here to let me build a personalized skincare routine for you.
If you want to get more involved and pick my next topics or see exclusive behind the scenes content, don’t forget you can head over here and become a YouTube Channel Member!
