Cell Turnover

Cell turnover is the ongoing cycle in which new skin cells are produced in the lower epidermis, travel to the surface, and are eventually shed. It is the engine that keeps the skin surface fresh and continuously renewed.

The process begins at the base of the epidermis, where keratinocytes divide. As new cells push older ones upward, the older cells flatten, lose their nuclei and fill with keratin, ultimately becoming the protective dead layer of the stratum corneum before shedding through desquamation. In younger skin the full journey is relatively quick, but the cycle gradually lengthens with age, which is one reason mature skin can look duller and take longer to recover a smooth texture.

A slower cycle allows dead cells to linger, contributing to dullness, uneven tone, rough patches and congestion. Ingredients that support turnover work by encouraging renewal or by loosening the bonds between surface cells. Retinoids influence how keratinocytes mature and shed, while chemical exfoliants such as alpha and beta hydroxy acids help dissolve the connections holding dead cells in place.

• Retinoids act on the renewal process itself over weeks of consistent use.
• Hydroxy acids act more directly on the surface to smooth and brighten.

Because pushing turnover too hard can outpace the barrier's ability to recover, gradual introduction and adequate moisturising are generally recommended alongside these actives.