Product

Paula's Choice BOOST C15 Super Booster

15% pure L-ascorbic acid with vitamin E and ferulic acid, in opaque packaging. The closest thing on this list to the classic clinical formula.
At a Glance
Recommended

BOOST C15 follows the three-ingredient system the published photoprotection research is built on: L-ascorbic acid, vitamin E and ferulic acid. Together they protect better than vitamin C alone, and the combination helps stabilize the vitamin C. This serum runs it at 15% L-ascorbic acid.

L-ascorbic acid is the best-studied form of vitamin C, for brightening and collagen. Its weakness is stability — it dies in air and light — so the opaque, air-restricting packaging here is doing real work, and yellowing means it is losing potency.

At 15% and a low pH, it can sting reactive skin. Paula's Choice adds bisabolol, panthenol and licorice to take the edge off, but sensitive skin should still ease in.

Key facts

Key activeL-ascorbic acid 15% + ferulic acid + vitamin E
TextureLightweight liquid
Best forAnyone wanting the evidence-backed vitamin C formula
Approximate price$46–$49
FragranceFragrance free

How it works

This is the textbook formula. 15% L-ascorbic acid, vitamin E, ferulic acid — the same three-ingredient system that the published photoprotection research is built on, and the same one SkinCeuticals uses at three times the price.

Paula's Choice publishes the concentration on the ingredient panel: "Ascorbic Acid 15.0%." Almost nobody else in this category does that, and it deserves credit.

Opaque packaging with an air-restricting dropper. They clearly understand that vitamin C dies in air.

Soothing extras — bisabolol, panthenol, licorice — are there to take the edge off the low pH.

Everyday habits

How to use it
  • When: morning suits an antioxidant serum, under sunscreen.How much: a few drops on clean skin. Steps: apply before moisturizer and let it absorb. Sunscreen: vitamin C is not sun protection — always follow with SPF in the day. Storage: keep it away from light and heat, and replace it if it darkens.
Who should be careful+

15% L-ascorbic acid stings, particularly on reactive skin. This is the trade for using the form that actually has evidence.

20 ml is a small bottle for $49. Cost per ml is high — Timeless gives you more L-ascorbic acid for less.

The new separate-dropper packaging is fiddly and has confused a lot of buyers.

It will oxidize once opened. Store it away from light and heat, and replace it when it darkens.

Questions people ask+
Is this the classic vitamin C formula?Close. It runs the L-ascorbic acid, vitamin E and ferulic acid system at 15%.
Will it sting?It can, at 15% and low pH. Soothing extras help; ease in if sensitive.
Why is the bottle small?It is 20 ml, so cost per ml is high. You are paying for the formula and packaging.
Is it fragrance-free?Yes. The formula is fragrance-free.
Do I still need sunscreen?Yes. Vitamin C does not replace SPF.
Full ingredient list+

Water, Ascorbic Acid, Glycerin, Ethoxydiglycol, PPG-26-Buteth-26, Mannitol, Tridecapeptide-1, Palmitoyl Tripeptide-5, Ergothioneine, Sodium Hyaluronate, Pentylene Glycol, PEG-40 Hydrogenated Castor Oil, Bisabolol, Sodium Gluconate, Decylene Glycol, Ferulic Acid, Oryza Sativa Bran Extract, Tocopherol, Polyacrylate Crosspolymer-6, 1,2-Hexanediol, Panthenol, Sodium Phytate, Sodium Hydroxide, Citric Acid, Phenoxyethanol

References+

1. Ferulic acid stabilizes a solution of vitamins C and E and doubles its photoprotection of skin (https://doi.org/10.1111/j.0022-202X.2005.23768.x) — Establishes the exact three-ingredient system cited on the page — 15% L-ascorbic acid + 1% alpha-tocopherol (vitamin E) + ferulic acid — showing ferulic acid improves vitamin C/E chemical stability and doubles UV photoprotection of skin. 2. A topical antioxidant solution containing vitamins C and E stabilized by ferulic acid provides protection for human skin against damage caused by ultraviolet irradiation (https://doi.org/10.1016/j.jaad.2008.05.004) — In vivo human clinical trial confirming that the 15% L-ascorbic acid, 1% alpha-tocopherol, 0.5% ferulic acid formulation provides significant UV photoprotection — the 'published photoprotection research' the page refers to. 3. Topical L-ascorbic acid: percutaneous absorption studies (https://doi.org/10.1046/j.1524-4725.2001.00264.x) — Shows L-ascorbic acid must be formulated at a low pH (below 3.5) to penetrate skin, supporting the page's statements about the product's inherently low pH and why 15% L-ascorbic acid can sting. 4. The Roles of Vitamin C in Skin Health (https://doi.org/10.3390/nu9080866) — Peer-reviewed review documenting topical vitamin C's antioxidant protection against UV-induced photodamage and its role in collagen synthesis, backing the general scientific rationale for a 15% L-ascorbic acid serum.