Vitamin C is one of the most popular actives, and with good reason: it is an antioxidant that also evens out the tone. But it has its quirks — forms, stability and combinations — and without understanding them it is easy to end up with "it does not work".
Vitamin C neutralises free radicals (protection against photoageing), boosts the action of sunscreen, supports collagen synthesis and evens the tone by slowing melanin production. L-ascorbic acid is the most active but least stable form; derivatives are more stable and gentler. It is best used in the morning under sunscreen.
01What vitamin C does
It is a powerful antioxidant: it neutralises the free radicals formed under UV and so helps protect against photoageing — especially paired with sunscreen. In addition it supports collagen synthesis and evens the tone by slowing the formation of melanin. So it is useful both against pigmentation and for radiance.
02Forms and stability
The main difficulty with vitamin C is stability: it oxidises in light and air. Hence the choice of form:
L-ascorbic acid or derivatives
L-ascorbic acid (LAA)
- Strength
- The most studied and most active form
- Drawback
- Unstable, low pH, can irritate
- For whom
- Normal/resilient skin, not reactive
Derivatives
- Examples
- 3-O-ethyl ascorbic acid, ascorbyl glucoside, MAP
- Advantage
- More stable, gentler, higher pH
- For whom
- Sensitive and reactive skin
A stability tipLook for L-ascorbic acid in a dark/opaque bottle, often with vitamin E and ferulic acid — they stabilise the formula. If a serum has darkened (turned yellow-brown), the vitamin C has oxidised and lost its strength.
03How to use
- It is more often applied in the morning — under sunscreen, to strengthen photoprotection.
- With sensitive skin, start at a low concentration (5–10%) or with a derivative.
- Store it protected from light and air; watch the colour.
- Combine it with strong acids (AHA/BHA) with care — it can irritate.
04Common questions
Does vitamin C replace sunscreen?
No. It strengthens photoprotection by neutralising free radicals, but it does not filter UV. Vitamin C and sunscreen are a team, not a substitute for each other.
Can I use vitamin C with niacinamide?
Yes. The myth of their incompatibility is out of date; in modern formulas they combine happily and complement each other.
05What to try
L-ascorbic acid 10–15% (+ E and ferulic)
Maximum activity for resilient skin.
Смотреть на YesStyle SerumA derivative (3-O-ethyl ascorbic acid)
More stable and gentler for sensitive skin.
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The article's key points draw on peer-reviewed publications:
This material is educational and does not replace a consultation with a dermatologist.