What is Active ingredient concentration?
The percentage of the ingredient that does the work.
Short answer
'With retinol' on the front but no percentage on the box.
Active ingredient concentration when buying a skin care
The percentage of the ingredient that does the work.
Why it matters: Niacinamide works at 2–5%; vitamin C at 10–20%; salicylic acid at 0.5–2%. Below that, you're buying marketing.
Look for: 'With retinol' on the front but no percentage on the box.
Full Skin Care buying guide