Compare Products: The Niacinamide 15 Serum vs C.E.O. 15% Vitamin C Brightening Serum

Who It's Designed For

COSRX
  • Oily and acne-prone skin seeking serious oil control
  • Post-acne marks and hyperpigmentation
  • Enlarged pores and textured skin
  • Users ready to step up from 10% to higher-strength niacinamide
  • Those who prefer minimal-ingredient formulas
Sunday Riley
  • Those who want a stable vitamin C that will not oxidize or change color
  • Users who find L-ascorbic acid serums too irritating or acidic
  • People who enjoy a citrus-scented skincare experience
  • Those seeking a vitamin C serum that does not require refrigeration
  • Users looking for a luxurious texture that layers well under makeup

Key Ingredients

COSRX

Niacinamide (15%), Acetyl Glucosamine (2%), Zinc PCA (1%), Allantoin (0.1%)

Sunday Riley

15% Tetrahexyldecyl Ascorbate (THD Ascorbate), Squalane, Glycolic Acid, Tocopherol (Vitamin E), Saccharide Isomerate

Product Composition

14% similarity (5 ingredients in common)

Shared Ingredients
water1ethylhexylglycerinsodium phytatetocopherol
Only in COSRX (11)
pentylene glycolniacinamidebutylene glycolacetyl glucosamine2-hexanediolzinc pcatrehalosexanthan gumpullulanallantoincitric acid
Only in Sunday Riley (20)
tetrahexyldecyl ascorbatesqualanepolyglyceryl-6 distearatepeg-8 beeswaxlimonenecitrus sinensis (sweet orange) oilcitrus tangerina peel oilglycine soja sterolshydrogenated polydecenephenoxyethanolacetamidoethoxyethanoljojoba estersglycolic acidcaprylyl glycolcitrus aurantium dulcis (sweet orange) oilchlorphenesincera albaisosqualanec30 hydrocarbonssaccharide isomerate

User Feedback Patterns

COSRX
Oil control standout

Users consistently report significant reduction in daytime oil and shine. Many describe it as the best niacinamide serum they have tried for sebum control.

Lightweight texture praised

Unlike some high-concentration serums, this absorbs quickly without tackiness or residue. Layers well under other products.

Small bottle concern

The 20ml size (vs. 30ml standard) is a common gripe, especially given the price point.

Pore improvement takes time

Users report visible pore improvement around the 3-4 week mark with consistent twice-daily use.

Sunday Riley
Luxurious texture

Users consistently praise the lightweight oily texture that absorbs well and sits beautifully under makeup. The application experience is rated higher than most L-ascorbic acid serums.

Pleasant citrus scent

The orange scent is frequently mentioned as a positive. Users who enjoy scented skincare rate this highly. However, fragrance-sensitive users avoid it.

No oxidation concerns

Users appreciate that the golden color remains consistent throughout the product's life. No anxiety about darkening or wasting product due to oxidation.

Gradual brightening results

Brightening results are described as gradual but visible over 4-8 weeks. Some users expecting the immediate 'glow' of L-ascorbic acid find the results slower.

Which Should You Buy?

COSRX The Niacinamide 15 Serum offers great value at a lower price point. Sunday Riley C.E.O. 15% Vitamin C Brightening Serum may be worth the premium if you want 15% Tetrahexyldecyl Ascorbate (THD Ascorbate).

Budget Pick
Buy COSRX

View Full Product Details

Related Comparisons