Blog / Ingredients

Vitamin C in skincare: L-ascorbic acid vs derivatives

By The regimen team · June 24, 2026 · 1 min read

Vitamin C is a morning antioxidant that brightens skin, fades dark spots, and adds a layer of protection against daily free-radical damage. The catch is that not all "vitamin C" is the same.

L-ascorbic acid vs derivatives

  • L-ascorbic acid is the most studied and potent form — but it's acidic, can sting, and oxidises (goes orange) over time.
  • Derivatives (sodium ascorbyl phosphate, ethyl ascorbic acid, THD ascorbate) are more stable and gentler, at the cost of some potency. Better for sensitive or reactive skin.

How to use it

  • Apply in the morning, before moisturiser and sunscreen.
  • Pair it with SPF — vitamin C and sunscreen are a classic protective duo.
  • Don't layer it with exfoliating acids in the same routine (two low-pH actives can destabilise and irritate) — keep acids for the evening. The conflict checker will flag this for you.

Vitamin C is a cornerstone for hyperpigmentation and aging concerns.

FAQ

When should I apply vitamin C?

In the morning, under sunscreen — its antioxidant protection complements SPF.

My vitamin C turned orange — is it still good?

Orange/brown means it has oxidised and lost potency. Store it cool and dark, and replace it.

Put this into practice

Build a routine and we’ll catch ingredient conflicts as you go — free.

Build your routine →

Related reading

regimen provides general educational information about skincare, not medical advice. Ingredient-conflict warnings and routine suggestions are informational and may be incomplete or wrong for your skin. Always patch-test, read product labels, and consult a dermatologist or physician for medical concerns.