Obagi Professional-C Serum 20% Review
The Verdict
Professional-C Serum 20% is Obagi's highest-strength vitamin C serum and the Best Sellers pick in the Professional-C range, but that popularity reflects an experienced audience rather than a beginner-friendly formula. It's a strong choice if you've already used a vitamin C serum without irritation and want maximum brightening potency from L-ascorbic acid. If you're new to vitamin C or your skin leans sensitive, Professional-C 10% is the safer starting point — you can always step up to 20% later.
Obagi Professional-C Serum 20% | High-Potency Vitamin C Antioxidant Serum | 30ml
£170.00
Obagi Professional-C Serum 20% is a fluid-texture vitamin C serum built on L-Ascorbic Acid plus Sodium Hyaluronate — the most concentrated of the three strengths in Obagi's Professional-C range, and the one carrying a Best Sellers tag on Skintique. It suits skin that's already comfortable with daily vitamin C and wants maximum brightening potency, and isn't the strength to reach for as your first-ever vitamin C serum.
What is Obagi Professional-C Serum 20%?
Obagi Professional-C Serum 20% is a fluid-texture vitamin C serum and the most concentrated of the three strengths in Obagi's Professional-C range, sitting above the 10% and 15% versions. Its headline active is L-Ascorbic Acid — the pure, well-studied form of vitamin C used in skincare — paired with Sodium Hyaluronate, a hydrating ingredient included to help offset some of the dryness or tightness that a higher-strength acid serum can bring for some users. Obagi's own product listing also names Ascorbyl Glucoside, a stabilised vitamin C derivative, as a supporting ingredient alongside the two headline actives. On Skintique's own store, this is the Professional-C strength that carries the Best Sellers tag, which tells you it's popular among shoppers who already know their skin tolerates vitamin C well — not necessarily a sign it's the right first vitamin C serum to try. Obagi positions the wider Professional-C range as part of its professional-grade, dermatology-heritage skincare line, and the 20% strength sits at the top of that range's antioxidant potency.
Key ingredients
| Ingredient | Type | What it's included for |
|---|---|---|
| L-Ascorbic Acid (Vitamin C) | Antioxidant vitamin C | The headline active, helps improve the appearance of uneven tone and dullness |
| Sodium Hyaluronate | Humectant | Helps attract and hold moisture, supporting comfort at this strength |
| Ascorbyl Glucoside | Vitamin C derivative | A stabilised form of vitamin C listed as a supporting antioxidant ingredient |
Who it's suitable for
Obagi's own skin-type listing for this product covers Normal, Oily, Combination and Mature skin — notably, Sensitive is not among the listed skin types for the 20% strength, unlike the 10% version. It's a strength most suited to a fairly specific audience rather than a general-purpose entry point, generally aimed at people who:
- Have already used a vitamin C serum — from Obagi or another brand — without irritation
- Want the most concentrated L-ascorbic acid option in the Professional-C range
- Are dealing with uneven tone, dullness or the visible effects of everyday environmental exposure
- Have normal, oily, combination or mature skin rather than a sensitive or reactive skin type
Who might want to hold off, or check with a professional first
First-time vitamin C users and anyone with sensitive or reactive skin generally aren't the ideal starting point for the 20% strength — Obagi's own Professional-C 10% exists specifically to serve that group instead. A patch test is worth doing before full-face use at any vitamin C strength, and it matters more here given how concentrated this formula is. If you're pregnant or breastfeeding, please contact our team for advice before use.
How Professional-C 20% compares to 10% and 15%
All three Professional-C strengths share the same core active — L-ascorbic acid vitamin C — so the difference between them isn't what they do, it's how much of it your skin gets in one application. Professional-C 10% is the gentlest and the only one of the three that lists sensitive skin among its suitable types. Professional-C 15% sits in the middle, a step up for skin that's already tolerated daily vitamin C. Professional-C 20%, reviewed here, is the strongest of the three and the only one confirmed to carry Sodium Hyaluronate alongside the vitamin C on its current product listing. For the full side-by-side breakdown across all three strengths, see our Professional-C 10% vs 15% vs 20% comparison, or read the individual reviews for Professional-C Serum 10% and Professional-C Serum 15%.
How to use it
Vitamin C serums like this are conventionally used once daily in the morning, applied to cleansed skin before moisturiser and sunscreen, since vitamin C is an antioxidant step that's typically paired with daily SPF rather than used as a standalone sun-protection product. We don't have Obagi's own step-by-step directions confirmed for this specific listing, so for exact frequency and any build-up guidance, follow the instructions on your product packaging or insert rather than relying on general convention alone. If you're introducing vitamin C to your routine for the first time, or stepping up from a lower strength, easing in every other day for the first week or two before moving to daily use is a sensible, low-risk approach — even though it isn't a formal Obagi instruction we can point to.
A patch test on a small area 24–48 hours before full-face use is worth doing, particularly at this concentration or if you have reactive or sensitised skin.
What to expect
Some people notice a brief tingling sensation on application with a high-strength vitamin C serum like this — that's a fairly normal response as skin adjusts to a concentrated acid, and it tends to settle with continued use rather than persist. Vitamin C serums are generally used to help improve the appearance of uneven tone and dullness over time with consistent use, though how quickly any visible change shows up varies from person to person and depends on skin type, starting condition and how consistently the product is used. If you experience ongoing irritation, redness or stinging that doesn't settle, it's worth dropping back to a lower strength — such as Professional-C 15% or 10% — or pausing use and seeking advice.
Professional-C 20% vs Obagi-C Fx Clarifying Serum
It's easy to assume every Obagi vitamin C product works the same way, but Professional-C 20% and Obagi-C Fx Clarifying Serum aren't quite interchangeable. Professional-C 20% is built around a single high-strength headline active — L-ascorbic acid — for maximum antioxidant potency. Obagi-C Fx Clarifying Serum takes a more targeted brightening approach, formulated with arbutin alongside its vitamin C content specifically to help address tone unevenness. If straightforward maximum-strength vitamin C is what you're after, Professional-C 20% is the more direct choice; if tone-evenness is your primary concern and you want an arbutin-containing formula, it's worth reading the Obagi-C Fx review before deciding.
Where it sits in the wider Obagi range
Professional-C 20% is one route into Obagi's vitamin C options, but not the only one. For a wider view of how the brand's brightening and antioxidant serums compare, see our guide to the best Obagi vitamin C serum for brightening and uneven tone, or start from the Obagi brand guide for an overview of how the full range — Professional-C, Obagi-C, Nu-Derm, ELASTIderm and more — fits together.
Storage and layering
Vitamin C serums, including L-ascorbic acid formulas like this one, are generally best kept away from direct sunlight and heat, with the cap replaced fully after each use to help protect the formula. Most people apply this type of serum after cleansing and before moisturiser and sunscreen, rather than layering it under or over other high-strength actives in the same application. If you're combining it with a retinol product elsewhere in your routine, using vitamin C in the morning and retinol in the evening is the more common approach, though how you build your own routine should reflect what your skin tolerates.
Ingredients glossary
Want more detail on the two headline actives in this formula? See our glossary entries on L-ascorbic acid and Sodium Hyaluronate.
Safety and patch testing
If you're pregnant or breastfeeding, please contact our team for advice before use. As with any high-strength active serum, introduce it gradually if you're new to this concentration, patch test first if you have sensitive or reactive skin, and stop use if irritation persists. Daily SPF is recommended alongside any vitamin C serum.