Vitamin C: A Practical Guide
L-ascorbic acid · SAP · MAP · Ethyl ascorbic acid · Ascorbyl glucoside · THD ascorbate
Vitamin C is an antioxidant; some formulas have evidence for improving the look of sun-aged skin and uneven tone. Evidence varies by formula and concern.
Label names (INCI): Ascorbic Acid, Sodium Ascorbyl Phosphate, Magnesium Ascorbyl Phosphate, 3-O-Ethyl Ascorbic Acid, Ascorbyl Glucoside, Tetrahexyldecyl Ascorbate, Ascorbyl Palmitate
Written by the Oliareen editorial teamDermatologist review: pendingLast updated: 6 November 2026How we write
Myth vs fact
- Myth
- Vitamin C can replace sunscreen.
- Fact
- No. Vitamin C isn't sunscreen and has no SPF. It may add some protection under sunscreen, but it can't take its place.
What it is
Vitamin C comes in many forms. Pure L-ascorbic acid (Ascorbic Acid) is the most studied but unstable and more likely to sting. Derivatives such as Sodium Ascorbyl Phosphate, 3-O-Ethyl Ascorbic Acid and Ascorbyl Glucoside are more stable and gentler, but less studied.
What it does
As an antioxidant it helps limit some damage from sun and pollution, plays a role in collagen, and slows pigment formation a little. Results take weeks to months and differ a lot between formulas.
Vitamin C is not sunscreen
Vitamin C doesn't block UV light and has no SPF or PA rating. Studies suggest it can add some antioxidant protection under sunscreen, nothing more. Out in Dhaka sun, wear a broad-spectrum sunscreen and reapply if you stay outdoors.
Often discussed for
This doesn't mean everyone with these needs it.
Concerns
Skin types
How to approach it
It's usually applied as a serum after cleansing. Keep the bottle closed and away from sun and heat. If the serum turns brown, it has oxidised; throw it out. Formula and stability matter more than the percentage.
Morning or evening
Many people use it in the morning under sunscreen, but evening works too. Avoid layering it with AHA, BHA or benzoyl peroxide in the same session, and keep copper peptides to a different time.
If you're new to it
Start one new active at a time and give it at least two to four weeks before adding another. Patch test first: a little on the side of the jaw or behind the ear for a few days. Keep the rest of the routine simple: a gentle cleanser, a moisturiser and sunscreen by day.
General education, not a diagnosis or treatment plan.
Works well with
Examples of common pairings, not guaranteed combinations.
Use carefully with
Stacking several actives raises the risk of irritation. If you're on any prescribed medicine, ask your doctor before adding an active.
- AHA (in the same session)
- BHA (salicylic acid) (in the same session)
- Benzoyl peroxide
- Copper peptides (in the same session)
- L-AA stings and oxidises (brown = discard)
- Safe in pregnancy
- Not photosensitising
Possible reactions
A few seconds of mild tingling or a little dryness can happen at first. Stop if burning doesn't settle, or if a red rash, itching, swelling or peeling keeps getting worse. Swelling of the face, lips or eyes, or trouble breathing, needs urgent medical care.
When to see a doctorEvidence and timing
- Evidence
- Evidence: strong
- Time to see a change (weeks)
- 2-4 glow; 8-12 pigment/lines
Evidence comes from studies of specific formulas and strengths. Your product may behave differently.
Questions people ask
Why did my vitamin C serum turn orange or brown?
Air, light and heat oxidise vitamin C. Once it's clearly brown, it won't do much; throw it out.
Why does vitamin C sting?
Pure L-ascorbic acid needs an acidic formula to work, which can sting sensitive skin. A gentler derivative or using it every other day may help. Stop if the stinging doesn't settle.
Can vitamin C replace sunscreen?
No. If you're out in daylight you still need sunscreen. See the section below.
Is vitamin C okay in pregnancy?
It's generally considered safe. Still, check with your doctor before changing your routine in pregnancy.