A moisturizer is a tool, not a treatment

Moisturizers sit at the bottom of the skincare status hierarchy, below every acid and every serum, and they have a better evidence base than almost anything above them. Emollients and moisturizers for eczema have been through Cochrane review. That is a higher bar than most of the actives people agonize over.

What they do is narrow and real: they reduce water loss through the stratum corneum and give the barrier the conditions to repair itself. Barrier recovery is signalled by transepidermal water loss, and the repair runs on roughly a two-week cycle. A moisturizer does not speed that up. It stops you interrupting it.

It will not remodel collagen. It will not clear acne. It will not fade pigment. When a moisturizer appears to do those things, the usual explanation is that the skin was inflamed and irritated, the barrier settled, and the improvement was subtraction rather than addition.

That is worth knowing because it changes what you should spend on. The moisturizer is the cheap, boring, load-bearing part of the routine.