Vitamin C is one of the few skincare ingredients with broad scientific agreement behind it, which is why it has become a fixture of the morning routine for anyone who takes facial care seriously. The market, however, is full of serums that lead with dramatic promises and big numbers on the label (10%, 15%, 20%), numbers that say little about quality on their own.
This guide explains what a vitamin C serum for the face does for skin, how the forms of vitamin C differ, why concentration is not the only criterion, and how to choose by skin type. There is no universal "best" vitamin C serum. There is the best serum for your skin, your goal and your routine. Once you understand forms, concentration and stability, label claims lose their pull. C E Ferulic is a good example of a formula built around those points, and we come back to it below.
Short answer
Among SkinCeuticals vitamin C serums: C E Ferulic is the choice if you want to reduce the look of fine lines and wrinkles and improve the look of skin firmness, for dry, normal, combination and sensitive skin. Phloretin CF is the choice if you want a more even-looking tone and less visible discolouration, for normal, oily and combination skin. Silymarin CF is the choice for oily and blemish-prone skin, when shine and visible pores bother you. According to the manufacturer's directions, all three serums are applied in the morning after cleansing, on dry skin, before the rest of your care; to choose one, compare your skin's needs in the table below.
Comparison: C E Ferulic, Phloretin CF and Silymarin CF
| Property | C E Ferulic | Phloretin CF | Silymarin CF |
|---|---|---|---|
| Main goal | fine lines, wrinkles, loss of firmness, radiance | uneven tone, discolouration, fine lines | shine, visible pores, texture, fine lines |
| Skin type and condition (per the manufacturer) | dry, normal, combination, sensitive | normal, oily, combination | normal, oily, combination, blemish-prone |
| Vitamin C (L-ascorbic acid) | 15% | 10% | 15% |
| Other highlighted actives | 1% vitamin E, 0.5% ferulic acid | 2% phloretin, 0.5% ferulic acid | 0.5% silymarin (milk thistle extract), 0.5% ferulic acid, 0.5% salicylic acid |
| How to apply | In the morning after cleansing, apply 4 to 5 drops to dry skin on the face, neck and décolleté, before the rest of your care. | In the morning after cleansing, apply 4 to 5 drops to dry skin on the face, neck and décolleté, before the rest of your care. | In the morning after cleansing, apply 4 to 5 drops to dry skin on the face, neck and décolleté, before the rest of your care. |
| Then | The rest of your care, then sunscreen. | The rest of your care, then sunscreen. | The rest of your care, then sunscreen. |
| Size | 30 ml | 30 ml | 30 ml |
Sources: C E Ferulic, Phloretin CF, Silymarin CF on skinceuticals.de (Germany), reviewed 11 October 2026.
C E Ferulic or Phloretin CF?
Both formulas contain pure vitamin C and ferulic acid. C E Ferulic has 15% vitamin C and vitamin E, while Phloretin CF has 10% vitamin C and phloretin instead of vitamin E. According to SkinCeuticals, C E Ferulic is recommended for reducing the look of fine lines and wrinkles, and Phloretin CF primarily for a more even-looking tone.
What vitamin C does for skin
Antioxidant protection
Skin meets UV radiation and environmental pollution every day, and both produce free radicals, unstable molecules that can damage skin cells. Vitamin C is an antioxidant that neutralises free radicals, which helps defend skin against extra oxidative stress during the day.
Support for collagen and firmness
Vitamin C is a necessary cofactor in collagen synthesis. Collagen is the structural protein that gives skin firmness and elasticity. Regular use of vitamin C on the skin supports its natural renewal processes and helps skin look firmer and healthier over time.
A more even-looking complexion
Vitamin C also acts on pigmentation by slowing excess melanin production, which over time helps the complexion look brighter and more even. Expect a gradual effect, not an overnight one.
Forms of vitamin C: pure L-ascorbic acid and derivatives
Pure L-ascorbic acid: the best studied, but sensitive to light and air
L-ascorbic acid is the original, biologically active form of vitamin C and the best studied in dermatological literature. Its weakness is chemical instability. Air, light and heat break it down and it loses potency, which is why many cheaper serums quietly stop doing what they were bought for, even when this is not obvious to the eye.
Derivatives such as sodium ascorbyl phosphate are more stable, but they generally penetrate skin more slowly and less effectively than pure L-ascorbic acid. Serious formulas are therefore usually built around pure L-ascorbic acid, paired with a solution for its main weakness: stability.
Why packaging and formulation protect stability
This is why the formulation matters more than the number on the label. Opaque, airtight bottles, partner antioxidants such as ferulic acid and vitamin E, and a carefully controlled pH are not marketing details. They decide whether a serum stays effective to the last drop or oxidises within a month of opening. A change of colour alone is not a reliable sign that C E Ferulic has lost its effectiveness; SkinCeuticals states that the formula can darken and remain effective.
How much does concentration really matter?
A higher percentage on the label does not automatically mean a better or more effective product. Beyond a certain point skin cannot take up more of the active ingredient, while very high concentrations can raise the risk of irritation, especially on sensitive skin.
The interplay of ingredients makes the real difference. Combining vitamin C with ferulic acid and vitamin E, known as a "CF" or "C E" formulation, is a way to improve the stability of vitamin C and to add layered antioxidant protection that a lone concentration cannot offer. In other words, a serum with 15% vitamin C in a well-built CF or C E combination can outperform a 20% serum without that synergy.
How to choose a vitamin C serum for the face by skin type
Dry, normal or sensitive skin
For dry, normal and sensitive skin, where antioxidant protection, firmness and fine lines are the priority, C E Ferulic is the choice. It combines 15% pure vitamin C (L-ascorbic acid) with vitamin E and ferulic acid. It visibly firms, brightens and reduces the appearance of fine lines.
Oily, combination and blemish-prone skin
For oily and blemish-prone skin a light texture is essential, so the serum does not weigh skin down or add shine. Silymarin CF is a vitamin C antioxidant serum for oily and blemish-prone skin. It helps reduce excess shine and the appearance of pores and refines skin texture. If blemishes and first signs of ageing are both on your list, Blemish + Age Defense works on blemishes, excess oil and the look of fine lines in one step.
Discolouration and uneven tone
For more pronounced dark spots and uneven tone, Phloretin CF is the targeted option. It is a daytime serum that combines 2% phloretin, 10% pure vitamin C and 0.5% ferulic acid. It helps even the look of skin tone and reduce the appearance of discolouration and fine lines, and suits normal, oily and combination skin.
How to use vitamin C serum
Apply vitamin C serum in the morning to cleansed, dry skin, before moisturiser and sunscreen. A few drops (usually 4 to 5), pressed gently into face and neck, are enough. If your skin is new to vitamin C, start with every second day and build up slowly to lower the risk of irritation, especially on sensitive skin.
Vitamin C and SPF: an inseparable pair
Vitamin C supports daily sun protection and never replaces it. Without daily SPF the antioxidant benefit of vitamin C is weakened, because skin keeps taking the same UV exposure the serum is meant to counter. After vitamin C, follow with a sunscreen such as Ultra Facial UV Defense SPF 50+, a lightweight daily SPF that layers comfortably under makeup. If discolouration is a concern, Advanced Brightening UV Defense SPF 50 adds brightening care: it helps prevent sun-induced discolouration and improves the look of existing dark spots.
Common mistakes
The most common mistake is skipping SPF. Vitamin C without sun protection loses much of its point. The second is stacking too many actives at once (for example vitamin C, strong acids and retinol in the same routine), which raises the risk of irritation instead of speeding up results. The third is expecting speed. Vitamin C works cumulatively over weeks of consistent use, not overnight.
A fourth, often overlooked mistake is storage. A bottle left in the light, kept in a bathroom with swings in temperature and humidity, or left open for too long oxidises faster. Follow the storage and use-by directions on the pack; with C E Ferulic, a change of colour alone is no reason to conclude that the serum has lost its effectiveness.
Frequently asked questions
Can vitamin C be combined with hyaluronic acid?
Yes, the two are commonly used together in one routine. After a vitamin C serum you can add Hydrating B5 Gel, a lightweight, oil-free gel for all skin types, or, for more intensive hydration, H.A. Intensifier Multi-Glycan, which boosts the skin's own hyaluronic acid levels for visibly plumper skin.
Vitamin C in the morning or in the evening?
Morning use is recommended because of the antioxidant protection through the day and the pairing with sunscreen. In the evening skin runs its own renewal processes, so other targeted actives are usually used then. Anyone who clearly prefers evening use is not making a mistake, but loses part of the daytime synergy with SPF.
How long until results show?
Depending on goal and skin type, first signs of a more even, fresher-looking complexion can appear after a few weeks of consistent use, while effects on firmness build up gradually over a longer period. The key word is consistency. Skipping several days a week slows results down.
Explore authorized SkinCeuticals vitamin C serums
Skin2Glow is an authorized SkinCeuticals retailer based in Vienna, delivering original products to Austria, Germany, Croatia and Slovenia. Browse the full range of vitamin C serums and choose the formula that fits your skin type.
- Free shipping on orders over €95
- Free tester on orders over €100
- Free gift of your choice on orders over €200
