The order to apply things, and what actually clashes.

Almost every question about routine order is answered by a single rule: water before oil, thinnest to thickest. Skincare products are mostly either water-based or oil-based, and an oil layer is a barrier. Put the oil on first and the water-based serum that follows has nowhere to go. Put the water phase on first and the oil seals it in. That is the whole principle, and once you have it you can order any set of products, including ones I have never seen.

In practice, mornings: cleanse, or just water if your skin is dry. Then your water-based serum, which for most women in the transition is the barrier step, niacinamide. Then any oil-based serum, which includes our vitamin C, because it uses an oil-soluble form. Then sunscreen, always last of the actives and never skipped, because it protects more collagen than every serum in the cabinet combined.

Evenings: cleanse properly, since this is the wash that matters. Water-based serum again. Then your evening active, bakuchiol if you are using it. Then, on tight nights, a few drops of face oil as the genuine last step, ideally while skin is still slightly damp.

“Water before oil. Everything else in a routine is a detail arranged around that one sentence.”

Now the clashes, sorted into the real and the imaginary. Genuinely worth separating: a retinoid and a strong exfoliating acid on the same night, which is a reliable way to strip a barrier that is already thinning. Alternate nights rather than stacking. Benzoyl peroxide applied at the same time as a retinoid can degrade it, so if you use both, use them at opposite ends of the day. And more than two actives at once on perimenopausal skin is usually the cause of the reactivity people then blame on one product.

Now the imaginary ones. Niacinamide and vitamin C do not cancel out; that story comes from heating niacinamide in strong acid in a laboratory and has nothing to do with your bathroom. Bakuchiol, which is the one I am asked about most, is not the problem people expect: it does not carry retinol's photosensitivity and it layers happily with niacinamide, vitamin C, peptides and oils. If you are searching for what not to mix with bakuchiol, the honest answer is that the caution list is very short, and the one combination I would actually avoid is bakuchiol stacked with a prescription retinoid and an acid on the same night, which is not a bakuchiol problem but a too-much problem.

Two details that matter more than people expect. Apply water-based serums to slightly damp skin, because humectants pull water from whatever is nearest and you would rather that be the surface film than the deeper layers. And give each layer a moment, thirty seconds or so, rather than pressing the next on top immediately. That is not ceremony, it stops products pilling and rolling off.

The principle underneath all of it, and the one I would want you to leave with: in this decade the answer is fewer actives used consistently, not more used occasionally. A thin barrier cannot absorb a maximalist routine, and every one of the results worth having comes from eight to twelve weeks of the same simple sequence rather than from the sixth product. If you are choosing what to cut, keep sunscreen and the barrier step. Everything else is negotiable.

Davina Hearne, Naturopath (Diploma, NZ) · Founder, Valentia

Educational only. Always speak to your healthcare provider about your symptoms and before starting a new supplement.