How often do skin cells regenerate?

How does skin renewal work?

Stem cells in the deepest layer of the epidermis produce new cells. Their descendants divide, then mature and move upward toward the surface. Keratinocytes, the main cells involved in this process, eventually become flattened, dead surface cells that shed naturally. The epidermis keeps making replacement cells without requiring a product called "Renewal" to get started.1

Cell renewal does more than replace what sheds. As epidermal cells mature, they help produce substances that hold moisture and lipids that seal the spaces between cells. The resulting barrier helps prevent water loss and protects against environmental damage. Dead surface cells are part of the barrier, not packaging your skin forgot to throw away.12

Is the 28 day number exact?

No. About 28 to 30 days is one estimate for complete epidermal renewal; another estimate is 40 to 56 days. Use these as an approximate timescale, not a personal countdown. Renewal happens continuously, so cells are being produced, maturing and shedding at different stages rather than the whole surface being replaced at once.12

These turnover estimates refer to the epidermis, not every layer of skin. Beneath it, the dermis contains blood vessels, nerves, hair follicles and oil glands, and provides nutrients to the epidermis. The deeper subcutaneous layer contains fat and blood vessels. Collagen and elastin provide support and flexibility, so surface renewal is only one part of skin maintenance.3

Does skin regeneration slow with age?

Aging reduces cells' ability to divide and tissues' capacity to regenerate. Older skin also becomes thinner and more fragile, and repairs itself more slowly than younger skin. Wound healing is a separate process from routine surface turnover: diabetes, changes in blood vessels and reduced immunity also affect healing. A turnover estimate is not a deadline for a cut to close.23

How can you support your skin?

Protect skin from sun exposure, a major contributor to aging changes. Use sunscreen outdoors, including in winter, and protective clothing and a hat when needed. Keep skin moisturized with a lotion or another moisturizer, and avoid strongly drying or heavily perfumed soaps. Moist skin is more comfortable and heals more quickly. Be gentle with older, fragile skin: rubbing or pulling can cause tears.3