Ingredient evidence
What published studies do and do not show for skincare ingredients, graded A, B or C by the strength of the evidence.
AdenosineC
Adenosine: one placebo-controlled trial found smoother eye-area lines; evidence for acne scars, sensitive skin and pores is limited.
Azelaic acidB
Azelaic acid: some good trials for acne, melasma and acne marks, mostly at 15–20% (medicine strength in Korea); limited evidence for redness.
Centella asiaticaC
Centella asiatica (cica): a small trial found better skin hydration, and animal tests suggest low allergy risk. Acne and redness evidence is indirect.
Ceramide NPC
Ceramide NP is a skin-barrier lipid. Evidence is limited: one small uncontrolled study and a meta-analysis with no clear water-loss benefit.
Hyaluronic acid (sodium hyaluronate)B
Hyaluronic acid draws water into the skin's surface. One 4-week trial in dry elderly skin found more hydration but no change in water loss.
NiacinamideA
Niacinamide (vitamin B3): good trial evidence for visible dark spots; limited evidence for breakouts, skin barrier, oil and pores.
PanthenolC
Panthenol (provitamin B5): small studies in healthy skin found some hydration benefit and faster recovery from irritation caused in a test.
RetinolC
Retinol (vitamin A): limited evidence; the cited reviews are about prescription retinoids, and trials of retinol on its own are scarce.
Salicylic acidB
Salicylic acid (BHA): conditionally recommended for acne in the AAD 2024 guideline; oil and pore evidence is limited (no placebo-controlled trial).
Tranexamic acidB
Tranexamic acid: a 2026 global consensus lists topical use for acne marks and melasma; the two small 5% trials had no placebo group.