OBAGI - Professional-C® Serum 20%

Obagi Professional-C Serum 20%: Maximum-Strength Vitamin C Antioxidant Serum

Obagi Professional-C® Serum 20% is the highest-strength antioxidant serum in the Obagi Professional-C range. It combines 20% pure L-ascorbic acid with sodium hyaluronate to brighten and hydrate the complexion, strengthen antioxidant defences and improve the appearance of dark spots, fine lines and wrinkles.

Developed for normal-to-oily and combination skin, this fast-absorbing serum delivers a concentrated daily vitamin C treatment without leaving a heavy or greasy finish. It is particularly suited to experienced vitamin C users seeking Obagi’s maximum L-ascorbic acid concentration for visible radiance, smoother-looking skin and advanced protection against environmental oxidative stress.

Obagi identifies Professional-C Serum 20% as a bestselling formulation, recognised with the 2025 Allure Best of Beauty Award for Best Antioxidant Facial Serum.

What Does Obagi Professional-C Serum 20% Do?

• Delivers Obagi’s maximum 20% concentration of pure L-ascorbic acid.
• Brightens dull, tired and environmentally stressed skin.
• Helps improve the appearance of dark spots and uneven skin tone.
• Smooths the visible appearance of fine lines and wrinkles.
• Supports a firmer, more youthful-looking complexion.
• Strengthens the skin’s antioxidant defences against free radicals.
• Helps combat oxidative stress associated with blue light and infrared radiation.
• Provides complementary hydration through sodium hyaluronate.
• Absorbs rapidly with a lightweight finish suited to normal, oily and combination skin.

20% Pure L-Ascorbic Acid

L-ascorbic acid is the pure, biologically active form of vitamin C. It is one of the most extensively recognised antioxidant ingredients in advanced skincare and performs several connected functions within the complexion.

Advanced Antioxidant Defence

Ultraviolet exposure, pollution, infrared radiation and other environmental stressors can generate free radicals. These unstable molecules contribute to visible ageing by affecting the proteins, lipids and other structures responsible for healthy-looking skin.

The concentrated L-ascorbic acid in Professional-C Serum 20% helps neutralise free radicals and reinforces the skin’s natural antioxidant defences. Obagi has also evaluated the serum’s antioxidant potential against oxidative stress induced by blue light and infrared radiation.

Visible Brightening and Dark-Spot Support

Professional-C Serum 20% helps reduce the visible appearance of dark spots, discolouration and uneven tone. Consistent daily use promotes a clearer, brighter and more luminous-looking complexion.

The 20% strength makes this formulation particularly relevant for experienced vitamin C users whose priorities include stubborn-looking dullness, visible sun damage and more established uneven pigmentation.

Fine Lines, Wrinkles and Firmness

Vitamin C plays an important role in the biological processes associated with healthy collagen. By supplying a concentrated form of L-ascorbic acid, the serum supports visibly smoother and firmer-looking skin while helping minimise the appearance of fine lines and wrinkles.

Sodium Hyaluronate for a Hydrated Glow

Professional-C Serum 20% combines its maximum-strength vitamin C concentration with sodium hyaluronate, a moisture-binding form of hyaluronic acid.

This hydration support helps the skin appear smoother, plumper and more radiant while complementing the serum’s antioxidant and brightening activity. It gives the 20% formulation a distinctive combination of concentrated correction and lightweight hydration.

Reported Results

In Obagi’s consumer survey analysis:

• 91% of users reported that their skin appeared brighter and more hydrated.

Users commonly select the serum to support improvements in:

• Overall radiance and luminosity.
• The appearance of dark spots.
• Uneven-looking skin tone.
• Fine lines and wrinkles.
• Visible smoothness and firmness.
• Hydration without a heavy finish.

Participant-reported results from Obagi survey analysis. Individual results can vary.

Who Is Professional-C Serum 20% For?

The 20% concentration is particularly suited to:

• Experienced users of pure vitamin C.
• Normal-to-oily and combination skin.
• Dull or environmentally stressed complexions.
• Visible dark spots and uneven-looking pigmentation.
• Fine lines, wrinkles and reduced firmness.
• Skin showing established signs of photo-ageing.
• Anyone seeking the maximum L-ascorbic acid concentration in the Obagi Professional-C range.

Choosing Between Professional-C 10%, 15% and 20%

Obagi offers three Professional-C concentrations, allowing the formula to be selected according to skin type, experience and treatment objectives.

• Professional-C Serum 10% is the introductory concentration, particularly suited to dry, sensitive or vitamin C-naive skin.
• Professional-C Serum 15% provides an intermediate concentration for normal-to-combination skin.
• Professional-C Serum 20% delivers the maximum concentration and is designed primarily for normal-to-oily, combination and experienced skin.

The 20% formulation is the range’s most intensive option, combining concentrated L-ascorbic acid with sodium hyaluronate for brightening, antioxidant defence, visible age support and hydration.

Read our complete Obagi Professional-C Serum 10%, 15% and 20% guide for a detailed explanation of each concentration.

How to Use Obagi Professional-C Serum 20%

1. Cleanse and tone the skin.
2. Allow the face to dry before application.
3. Dispense approximately five to seven drops onto the fingertips.
4. Apply evenly across the face, neck and upper chest.
5. Allow the serum to absorb before applying moisturiser.
6. Complete the morning routine with broad-spectrum sunscreen.

Use once daily, preferably during the morning. Experienced users can apply it consistently each day, while anyone changing from a lower concentration can introduce the 20% formula progressively according to skin tolerance.

Building an Obagi Morning Routine

Professional-C Serum 20% occupies the concentrated antioxidant step immediately after cleansing and toning.

A complete morning order may include:

1. Obagi cleanser.
2. Obagi toner, when used.
3. Professional-C Serum 20%.
4. Additional targeted serum, when required.
5. Obagi Hydrate Facial Moisturiser.
6. Broad-spectrum sunscreen.

For an additional hydration-focused serum step, Obagi Daily Hydro-Drops can be layered after Professional-C Serum has absorbed and before moisturiser.

Vitamin C and Sunscreen

Professional-C Serum and sunscreen perform different but complementary roles. Vitamin C strengthens antioxidant protection against environmental free radicals, while sunscreen helps shield the skin from ultraviolet radiation.

Combining the 20% serum with daily broad-spectrum SPF creates an advanced morning defence strategy while supporting improvements in brightness, tone and visible signs of photo-ageing.

Texture, Colour and Formula Stability

Professional-C Serum 20% has a lightweight texture designed to absorb quickly into normal-to-oily and combination skin. Its dropper format allows the concentrated serum to be distributed precisely across the face, neck and upper chest.

L-ascorbic acid is naturally sensitive to air, heat and prolonged light exposure. Appropriate storage helps preserve the serum after opening.

• Keep the bottle tightly closed between applications.
• Store it in a cool, dark and dry location.
• Keep it away from direct sunlight and excessive heat.
• Do not leave the dropper exposed for extended periods.
• Use within three to six months after opening.

Obagi vitamin C serums can naturally range from clear to amber in colour. This variation can occur because of the nature of the antioxidant formula.

Frequently Asked Questions

Is Obagi Professional-C 20% the strongest serum in the range?

Yes. It contains the maximum L-ascorbic acid concentration available across Obagi Professional-C Serum 10%, 15% and 20%.

What type of vitamin C does it contain?

It contains L-ascorbic acid, the pure and biologically active form of vitamin C used for antioxidant protection, brightening and visible age support.

Does Professional-C Serum 20% contain hyaluronic acid?

Yes. The formulation contains sodium hyaluronate, a moisture-binding form of hyaluronic acid that supports hydration, smoothness and a visibly plumper complexion.

Can it help with dark spots?

Professional-C Serum 20% is formulated to improve the appearance of dark spots, uneven pigmentation and dullness while promoting brighter, more even-looking skin.

Can it improve fine lines and wrinkles?

Yes. Its concentrated L-ascorbic acid supports the biological processes associated with healthy collagen and helps improve the visible appearance of fine lines, wrinkles and reduced firmness.

Is Professional-C 20% suitable for oily skin?

Yes. Obagi positions the 20% strength primarily for normal-to-oily and combination skin. Its lightweight, fast-absorbing texture makes it easy to incorporate without adding a heavy moisturising layer.

Can it be used every day?

Yes. Professional-C Serum 20% is developed as a daily antioxidant treatment. Those progressing from a lower concentration can introduce it gradually before moving to consistent daily application.

Can I use it with retinol?

Vitamin C and retinol can form complementary parts of an advanced skincare programme. Professional-C Serum is commonly used in the morning, with retinol reserved for the evening.

Does vitamin C replace sunscreen?

No. Use Professional-C Serum beneath a separate broad-spectrum sunscreen to combine antioxidant support with ultraviolet protection.

Why might the serum tingle?

A brief tingling sensation can occur with concentrated L-ascorbic acid, particularly when moving from a lower vitamin C strength. Severe or persistent discomfort is a reason to stop application and seek appropriate advice.

Product Details

• Product: Obagi Professional-C® Serum 20%
• Size: 30ml
• Vitamin C: 20% L-ascorbic acid
• Additional key ingredient: Sodium hyaluronate
• Format: Lightweight antioxidant facial serum
• Skin types: Normal-to-oily and combination skin
• Use: Once daily, preferably in the morning
• Primary concerns: Dark spots, dullness, uneven tone, fine lines, wrinkles and environmental ageing

Important Information

For external use only. Avoid direct contact with the eyes, nose, mouth and lips. A temporary mild tingling sensation can occur. Discontinue use and seek appropriate advice if tingling becomes severe or irritation persists.

Product formulations and ingredient declarations can be updated. Always check the ingredient list printed on the product supplied before use, particularly if you have known allergies or sensitivities.

Related vitamin C products and information

• Obagi Professional-C Serum 10%, 15% and 20% guide
• Obagi Professional-C Serum 10%
• Obagi Professional-C Serum 15%
• How to layer serums, moisturiser and sunscreen
• Explore the Obagi Medical skincare range

Sources

• Pinnell et al. 2001, Topical L-ascorbic acid: percutaneous absorption studies, Dermatol Surg (PubMed 11207686)
• Obagi: Professional-C Serum 20% product page

Reviewed October 2026 by Skin by Science.

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