Vitamin C: Types, Stability & Best Formulas

Vitamin C remains a cornerstone of effective skincare, renowned for its antioxidant properties, collagen stimulation, and brightening effects.

This guide breaks down its various types, addresses stability challenges, and highlights optimal formulations for maximum efficacy.

Types of Vitamin C

L-Ascorbic Acid (LAA) is the purest, most potent form, requiring low pH (below 3.5) for absorption but prone to rapid degradation. Derivatives like Sodium Ascorbyl Phosphate (SAP), Magnesium Ascorbyl Phosphate (MAP), Ascorbyl Glucoside, 3-O-Ethyl Ascorbic Acid (EAA), and Tetrahexyldecyl Ascorbate (THDA) offer improved stability; SAP and MAP suit sensitive skin with neutral pH compatibility, while oil-soluble THDA penetrates deeper. Each converts to active vitamin C in the skin, balancing potency with gentleness.

Stability Challenges

Vitamin C oxidizes easily when exposed to air, light, or water, especially LAA, which browns and loses efficacy without stabilizers like ferulic acid or vitamin E. Derivatives excel here—EAA remains 50 times more stable than LAA, and THDA maintains potency for over 24 months in airtight, opaque packaging. Optimal formulations control pH at 5-6.5 for derivatives, using encapsulation to shield against environmental stressors.

Best Formulations

For beginners or sensitive skin, opt for 10-20% EAA or Ascorbyl Glucoside serums, stable and non-irritating with hyaluronic acid for hydration. Anti-aging benefits shine in THDA or MAP at higher concentrations, paired with niacinamide for barrier support. Acne-prone skin benefits from SAP’s antimicrobial action; always combine with sunscreen and store cool/dark.

K-Beauty and C-Beauty Vitamin C Trends

K-beauty favors EAA and Ascorbyl Glucoside in ampoules with fermented extracts or centella for barrier repair and glow. C-beauty emphasizes 10-20% vitamin C serums with TCM herbs and liposomal delivery for whitening and pollution defense, growing at 22.7% CAGR. Both prioritize encapsulation for stability, delivering irritation-free luminosity.