The question we get most often isn't 'what should I use?' — it's 'in what order?' Once you understand the underlying logic, product sequencing becomes intuitive rather than prescriptive.
The Core Rule: Thinnest to Thickest
Apply products from thinnest consistency to thickest — water-based toners and essences first, then serums, then moisturisers, then oils, then SPF (in the morning). Lighter, active-packed formulas need to reach the skin before denser, occlusive layers seal them out.
pH-Sensitive Actives
Some actives require a specific pH window to work. L-ascorbic acid and AHAs/BHAs work best at low pH (below 3.5). If you apply niacinamide directly after a low-pH acid, the acidic environment can temporarily affect niacinamide's efficacy. A 10–20 minute wait between actives resolves this, though the concern is often overstated in practice.
“Actives that conflict in theory often coexist perfectly well in practice — but when in doubt, separate them into morning and evening routines.”