Vitamin C serum for sensitive skin is a concentrated topical treatment formulated with gentler derivatives or lower concentrations (typically 5–10%) of Vitamin C to minimize irritation while delivering antioxidant benefits. While many standard face serums come in 30ml bottles, a 120ml size is a larger, “value-sized” or body-oriented bottle that is less common for high-potency facial actives but available from specific brands for extended use.
Why it’s different for Sensitive Skin
Standard Vitamin C (L-ascorbic acid) can be highly acidic (pH 3–3.5), which often causes stinging or redness in reactive skin. Sensitive-skin formulas focus on: 
Stable Derivatives: Ingredients like Ethyl Ascorbic Acid, Sodium Ascorbyl Phosphate, or Ascorbyl Glucoside are used because they are stable at skin-balanced pH levels (around 4.5–6).
Soothing Additives: Many are paired with Niacinamide (Vitamin B3) to strengthen the skin barrier, Vitamin E for moisturization, or Centella Asiatica to calm inflammation.
Irritant-Free: These formulas are typically fragrance-free and avoid harsh dyes or essential oils. 
Core Benefits
Gentle Brightening: Fades dark spots and hyperpigmentation by gradually slowing excess melanin production.
Antioxidant Shield: Neutralises free radicals from UV exposure and pollution, which is critical for sensitive skin that may have a compromised barrier.
Collagen Support: Stimulates protein synthesis to maintain skin firmness and reduce fine lines over time.
Redness Reduction: Anti-inflammatory properties help soothe the pink or red flush common in reactive skin types.