Browse our clinical A-to-Z of skincare ingredients — each profile breaks down the science, the strength of evidence, what it pairs with, what it clashes with, and which product type it actually belongs in.
Each ingredient is reviewed by our dermatology panel against published clinical literature. The evidence dots show how robust the data is — not how loud the brand is.
Vitamin A · All-trans retinol
The gold-standard anti-aging active. Speeds cell turnover, stimulates collagen, and softens fine lines — but only if you can tolerate the purge.
L-Ascorbic Acid · 10–20%
Brightens, fades pigment, and boosts SPF performance. Stability is the real issue — look for opaque, airtight packaging and a pH below 3.5.
Vitamin B3 · 2–10%
Calms redness, regulates sebum, and supports the skin barrier. Exceptionally well-tolerated and one of the few actives that plays nicely with almost everything.
Sodium Hyaluronate · Multi-weight
Holds up to 1,000× its weight in water. Multi-weight formulas hydrate at multiple depths — seal with an occlusive or it pulls moisture the wrong way in dry climates.
C9-dicarboxylic acid · 10–20%
The quiet workhorse. Treats rosacea, post-inflammatory hyperpigmentation, and mild acne with a far lower irritation profile than most acids.
Zinc Oxide · Titanium Dioxide · Tinosorb S
The single most evidence-backed anti-aging step. Mineral filters suit sensitive skin; modern hybrids (Tinosorb, Mexoryl) offer elegant, weightless UV coverage.
Most irritation comes from stacking the wrong actives. These are the layering rules our dermatologists actually follow at home.
Strips less from the barrier. Skip if you cleansed at night and your skin is balanced.
Best on freshly cleansed skin. Wait 60 seconds before the next step.
Hyaluronic acid or a peptide serum — anything that replenishes water content.
Two fingers of product. Reapply every 2 hours of direct sun exposure.
Stacking the wrong actives is the #1 cause of redness, peeling, and a compromised barrier. Memorize the pairs below.
Same routine, same night
Both accelerate turnover aggressively. Used together they wreck the barrier. Alternate nights or split AM/PM.
In the same formula
Older rumors of flushing are overstated, but high-strength L-ascorbic acid can lower niacinamide's efficacy. Apply at different times if you see sensitivity.
Layered together
Benzoyl peroxide oxidizes retinol on contact, neutralizing both. Use benzoyl in the morning, retinol at night.
Different formulations
Complementary, not conflicting. Retinol resurfaces; peptides signal repair. Use peptides in the morning if retinol dominates your night routine.
Universal layer
Truly inert. Sits between any active and your moisturizer to boost penetration without irritation.
Recovery stack
Counter-intuitively powerful. Ceramides replenish lipids lost during retinization, cutting purge time significantly.
Every ingredient profile is built on a literature review of peer-reviewed dermatology journals, weighted by study size, replication, and recency.
Take our 90-second skin profile and get a dermatologist-reviewed routine built from ingredients that actually have the data behind them.