Why does the complexion become duller with age?

Both governed by intrinsic and extrinsic factors, skin ageing is a natural process that no one can escape. Skin sagging, loss of flexibility and firmness, decrease in hydration, appearance of wrinkles... It manifests in various ways. The complexion also tends to become more dull with age. This is primarily due to the slowdown of cellular renewal that accompanies skin ageing. As a reminder, cellular renewal is a biological process by which the cells of the epidermis constantly renew themselves. Keratinocytes, representing about 80% of the cells of the epidermis, form in the basal layer and gradually migrate to the horny layer, where they die and form a protective barrier. This cycle takes about 28 days in young adults.

Between the ages of 30 and 70, cellular renewal decreases by approximately 50%.

A study has particularly focused on the transit time of cells in the epidermis, that is, the time required for cells to move to an adjacent layer, either from the basal layer to the Malpighian layer, from the Malpighian layer to the granular layer, or from the granular layer to the horny layer. Several volunteers aged between 18 and 80 were involved in the study and the dansyl chloride fluorescence method was used. First described in 1974, this method allows for the tracking of in vivo skin cell renewal and desquamation by fluorescence. The scientists observed an extended epidermal cell transit time of about ten days in older subjects compared to younger volunteers. The results according to age groups are compiled in the table below. The stars next to the numbers indicate that the increase in transit time is significant.