Skin renews continuously. New cells are produced in the basal layer; as they move upward they mature, lose their nuclei and become flattened, keratin-filled corneocytes at the surface, eventually shedding imperceptibly.
In healthy adult skin this cycle typically takes about 28 days, lengthening with age. A regular cycle contributes to smooth, vibrant-looking skin; accumulated dead cells can make skin look dull.
This has two practical implications: first, allow at least one cycle (4 weeks) before judging a new product. Second, exfoliation can support natural shedding, but overdoing it strains the barrier. A measured approach is always more sustainable.