The order to apply skincare, and why it matters less than you were told

Thin to thick, water before oil

A water-based serum cannot get through an oil layer, so it goes first. That is the whole of the physics. Within the water-based steps, the order changes results far less than anyone selling a seven-step routine wants you to believe.

The two exceptions worth respecting

Anything acidic wants bare skin to work at the pH it was formulated for, so it goes first among the water steps. And sunscreen always goes last, undiluted, in the quantity on the label — half a teaspoon for a face.

Three steps beats seven steps you skip

The routine you complete every night outperforms the one you abandon in week three. Cleanse, treat, moisturise. Add the fourth thing only once the first three are automatic.