Product

Sunday Riley CEO 15% Vitamin C Brightening Serum

15% THD ascorbate — a stable vitamin C derivative — at $85. Pleasant to use, and priced like a product with far stronger evidence behind it.
At a Glance
Mixed

The active is THD ascorbate, an oil-soluble vitamin C derivative. It works at normal skin pH, so it does not sting like L-ascorbic acid, and it is very stable — it will not turn brown. Of the derivatives, THD is among the better ones, and 15% is a real concentration.

But it is a derivative, not L-ascorbic acid, and the evidence gap between them is wide. The Ordinary sells a 20% THD ascorbate serum for a fraction of the price. You are paying largely for the sensory experience, which is genuinely nice.

The formula also contains low-level glycolic acid and citrus peel oils, which add some irritation potential — worth knowing if you expected a plain, gentle vitamin C.

Key facts

Key activeTHD ascorbate 15%
TextureLightweight, silky serum
Best forAnyone who wants a vitamin C that never stings
Approximate price$80–$85

How it works

The sensory experience is genuinely lovely, and that is not nothing — the serum you enjoy using is the one you keep using.

THD ascorbate is oil-soluble and works at normal skin pH, so it does not sting the way L-ascorbic acid does. It is also very stable — this will not turn brown on you.

15% is a real concentration of a derivative that has some supporting data. Of the derivatives, THD is among the better ones.

If pure vitamin C is off the table for your skin, this is a pleasant way to get something in the family.

Everyday habits

How to use it
  • When: morning or night.How much: a few drops on clean skin. Steps: apply before moisturizer and let the silky serum absorb. Sunscreen: vitamin C works on tone, so daily SPF helps results hold — follow with sunscreen. If it stings: it contains low-level glycolic acid and citrus oils; ease in if reactive.
Who should be careful+

At $85, you are paying flagship prices for a derivative. That is the honest headline. THD ascorbate is not L-ascorbic acid, and the evidence gap between them is wide. The Ordinary sells a 20% THD ascorbate serum for about $20.

The dropper bottle is a poor choice. Air enters every time you open it. THD is more stable than L-AA, so this matters less — but at this price, an airless pump should be standard.

It contains glycolic acid low in the formula. That can surprise people expecting a plain vitamin C, and it adds irritation potential.

Citrus oils are in there — a possible sensitizer.

Questions people ask+
Is this pure vitamin C?No. It is 15% THD ascorbate, a stable derivative.
Will it sting?The vitamin C will not, but the glycolic acid and citrus oils might.
Why does it cost so much?Largely the sensory experience; the active is cheaper elsewhere.
Is it fragrance-free?No. It contains citrus oils and fragrance components.
Does it oxidize?No. THD ascorbate is stable and will not turn brown.
Full ingredient list+

Water, Tetrahexyldecyl Ascorbate, Squalane, Polyglyceryl-6 Distearate, PEG-8 Beeswax, PPG-12/Smdi Copolymer, Glycine Soja Sterols, Sodium Phytate, Tocopherol, Acetamidoethoxyethanol, Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Sodium Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Jojoba Esters, Glycolic Acid, Caprylyl Glycol, Cetyl Alcohol, Polyglyceryl-3 Beeswax, Chlorphenesin, Glycerin, Polysorbate 60, Sorbitan Isostearate, Saccharide Isomerate, Citrus Aurantium Dulcis Peel Oil, Citrus Tangerina Peel Oil, Linalool, Limonene, Phenoxyethanol

References+

1. Topical Vitamin C and Its Derivatives in Cosmetic Science: Stability, Efficacy, and Formulation Strategies (https://brieflands.com/journals/jssc/articles/163798) — Peer-reviewed review confirming L-ascorbic acid requires a low acidic pH (2.0-3.5) and can irritate sensitive skin, while tetrahexyldecyl ascorbate is a lipophilic derivative that is stable at higher pH and penetrates skin more effectively, supporting the page's claims that THD is oil-soluble, works at normal skin pH, is stable, and does not sting like L-ascorbic acid. 2. Antioxidant Skincare Treatment for Hyperpigmented and Photodamaged Skin: Multi-Center, Open-Label, Cross-Seasonal Case Study (https://jcadonline.com/antioxidant-skincare-treatment-hyperpigmented-photodamaged-skin/) — Clinical study evaluating a 30% tetrahexyldecyl (THD) ascorbate serum that showed significant improvements in melanin, collagen, and hyperpigmentation, providing the supporting efficacy data referenced for THD ascorbate as a vitamin C derivative. 3. SUNDAY RILEY C.E.O. 15% Vitamin C Brightening Serum | Ulta Beauty (https://www.ulta.com/p/ceo-15-vitamin-c-brightening-serum-pimprod2007847) — Major retailer listing confirming the product's $85 price, 15% concentration, and THD ascorbate as an extremely stable, oil-soluble form of vitamin C. 4. What is Tetrahexyldecyl Ascorbate in Skincare? – Medik8 (https://www.medik8.com/pages/what-is-tetrahexyldecyl-ascorbate-in-skincare) — Clinical/educational source confirming THD ascorbate is a lipid-soluble, esterified vitamin C that is more stable than L-ascorbic acid, remains stable at skin-friendly pH (3-6.5), and is a gentler alternative without the stinging of L-ascorbic acid.