Paula’s Choice C15 Vitamin C Booster Review

The current Australian C15 formula combines 15% L-ascorbic acid with ferulic acid and tocopherol. Glycerin and glycols support hydration, while bisabolol adds a skin-conditioning, soothing role. This review concerns the current listed formula, not an older C15 ingredient list.

November 1, 2026

FORMULA NOTES / VITAMIN C

Paula’s Choice C15 Brightening Super Booster

A closer look at 15% ascorbic acid, its supporting ingredients and who the formula might suit.

A formulation-based review

Full ingredient list (INCI)

water/aqua/eau, ascorbic acid, dipropylene glycol, propanediol, glycerin, ethoxydiglycol, sodium hydroxide, ppg-26-buteth-26, peg-40 hydrogenated castor oil, bisabolol, ferulic acid, sodium phytate, decylene glycol, tocopherol, 1,2-hexanediol, sphingomonas ferment extract, phenoxyethanol

Source: Official product information, checked 1 November 2026. Check your packaging for formula changes.

Packaging image · Paula’s Choice

The focus

Dullness & uneven-looking tone

The format

20 mL lightweight serum

Price snapshot

A$84Australian official store · checked 1 Nov 2026

Worth knowing

15% ascorbic acid; pH 3.10–3.50

Product	Formulation Rating	Value Rating	Overall Rating
Paula’s ChoiceC15 Brightening Super Booster15% L-ascorbic acidA$84.00 · 20 mL	3.83★★★★★ ★★★★☆Antioxidant ★★★★☆Pigment Signalling ★★★★★Hydration	3★★★★★ A$42.00 per 10 mL; concentration-adjusted component uses 15% L-ascorbic acid.	3.42★★★★★

View the full comparison of 15 vitamin C serums

A lightweight antioxidant and hydration system

Who might it suit?

Dullness and uneven-looking tone: for someone seeking a disclosed ascorbic acid treatment.
A lightweight routine: suitable for people who prefer a thin serum under moisturiser.
Antioxidant-focused care: a supporting step alongside daily sunscreen, not a substitute for it.

Acidic vitamin C can still sting or irritate, even when a formula is marketed as gentle. Introduce gradually and stop if persistent irritation develops. Official product information.

What does the 15% refer to?

The disclosed 15% refers to L-ascorbic acid, the unmodified form of vitamin C. It is not a combined vitamin C complex or a derivative percentage. Supporting ingredient levels are not all disclosed, so their concentrations cannot be calculated from INCI order. Official product information.

Listed pH: 3.10–3.50.

Ingredients grouped by function

Ingredients are grouped by their estimated primary role in this formula; some ingredients have more than one function.

Function	Ingredients	Role in formula
Function: Primary Actives	Ingredients: ascorbic acid, bisabolol	Role in formula: Ascorbic acid anchors the treatment; bisabolol provides supporting skin-conditioning and soothing activity.
Function: Antioxidants	Ingredients: ferulic acid, tocopherol	Role in formula: Ferulic acid and tocopherol complement ascorbic acid.
Function: Humectants & Hydration Actives	Ingredients: propanediol, glycerin, decylene glycol	Role in formula: Propanediol, glycerin and decylene glycol support water binding and feel.
Function: Solvents	Ingredients: water/aqua/eau, dipropylene glycol, ethoxydiglycol	Role in formula: The aqueous glycol system dissolves and distributes the formula.
Function: Solubilizers	Ingredients: ppg-26-buteth-26, peg-40 hydrogenated castor oil	Role in formula: Support incorporation of ingredients with differing solubility.
Function: Preservatives & Antimicrobial Agents	Ingredients: 1,2-hexanediol, phenoxyethanol	Role in formula: Preservation and supporting antimicrobial function.
Function: Chelating Agents	Ingredients: sodium phytate	Role in formula: Binds metal ions to support formulation stability.
Function: pH Adjusters / Buffers	Ingredients: sodium hydroxide	Role in formula: Adjusts the finished product’s acidity.
Function: Texturisers & Rheology Agents	Ingredients: sphingomonas ferment extract	Role in formula: Film-forming and skin-conditioning support.

The key ingredients, explained

Ingredient	What it contributes
Ingredient: L-ascorbic acid · 15%	What it contributes: The central antioxidant ingredient and a cofactor in collagen-related biology. Topical performance still depends on the vehicle and stability.
Ingredient: Ferulic acid	What it contributes: A complementary phenolic antioxidant. Inclusion supports the design rationale without proving the exact synergy of a different tested formula.
Ingredient: Vitamin E	What it contributes: Lipid-phase antioxidant support. The label lists tocopherol without establishing the precise isoform composition.
Ingredient: Glycerin and glycols	What it contributes: Support water binding and a light feel.
Ingredient: Bisabolol and Sphingomonas ferment extract	What it contributes: Soothing/conditioning and film-forming support respectively; neither guarantees tolerance or a microbiome benefit.

An acidic antioxidant serum with supporting humectants

The aqueous solvent system keeps the texture light, while glycerin and glycols contribute water binding. Bisabolol is a useful supporting choice for comfort, but does not guarantee that a 15% acidic serum will suit reactive skin. Sphingomonas ferment extract is a film-forming and conditioning component; its presence is not evidence of a clinically demonstrated microbiome effect.

Reading the claims carefully

The brand reports expert-graded testing in 30 participants after four weeks and instrumental hydration testing in 31 participants after one week. The public summary does not provide full controlled results. Its suitability and non-irritation claims describe the tested conditions, rather than guaranteeing tolerance in every user. Vitamin E and ferulic acid percentages are not disclosed. Official product information.

What published vitamin C research tells us

These studies examined other formulations; they support ingredient rationale, not a claim that this serum has the same measured results.

Topical vitamin C and photoaged skin

A six-month placebo-controlled study of 5% vitamin C cream reported improvements in skin-surface and clinical measures. It used a different vehicle and concentration. Humbert et al., 2003.

Ascorbic acid and facial skin texture

A three-month split-face trial in 19 evaluable participants found improvements with another commercial serum versus vehicle. Its small sample and limited skin-type range constrain generalisation. Traikovich, 1999.

Our assessment

C15 offers a clearly disclosed ascorbic acid concentration and pH with a purposeful light hydration system. At the comparison snapshot price of A$84 for 20 mL, it costs A$42.00 per 10 mL. Its 3-star Value Rating places it in the middle of this comparison’s price-and-concentration value range. The smaller bottle should be considered alongside the headline price; texture, tolerance and moisture support matter more than assuming a premium price produces stronger results.

This serum earns an Overall Rating of 3.42 stars in our comparison of 15 ascorbic acid vitamin C serums.

Prices use the comparison snapshot of 1 November 2026; temporary promotions are excluded. Ratings are editorial assessments of formulation potential and value, not measured clinical outcomes.