No.5 Vitamin Concentrated Serum — Reddit Reviews

Name: No.5 Vitamin Concentrated Serum
Brand: numbuzin

by numbuzin

38mentionsacross 9 Reddit threads

Updated July 21, 2026

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What the community says

A K-beauty vitamin C and niacinamide serum favored for fading hyperpigmentation and brightening dull, combination skin but with a tendency to cause irritation and breakouts on sensitive types.

From Reddit

Backed by 9 threads from r/koreanskincare, r/tretinoin and 1 more.

Read the threads ↓

What people love

Contains melanin inhibitors effective for fading dark spots and acne scars
Combines niacinamide and vitamin C for brightening with a slightly moisturizing texture
Works well under makeup and delivers a dewy finish that many users enjoy

Watch out for

Causes redness and irritation, especially around sensitive areas like under the eyes
Can trigger breakouts and cystic acne for acne-prone or sensitive skin
Has a heavier texture that some find too rich or greasy, particularly in warmer weather