Skin’s internal clock could open opportunities for time-targeted cosmetics

Research has found that the skin operates on an internal 24-hour clock that controls its functions, from DNA repair to permeability and collagen production. The research opens opportunities for cosmetics formulators to develop more targeted morning and evening products that work with the skin’s natural rhythms. 

Dr. Diala Haykal, a specialist in aesthetic and anti-aging morphology medicine in France, led the research.

She found that every major skin cell type (keratinocytes, melanocytes, and fibroblasts) contains an autonomous molecular clock, referred to as the circadian clock. These clocks drive the skin’s natural rhythms in epidermal renewal, UV damage responses, and immune activity.

Due to this local clock, the skin knows when to carry out what functions. For example, according to Haykal, the skin’s barrier is most permeable in the evening, and its repair mechanisms peak at night.

She says the personal care industry can draw on these findings to move beyond static routines and develop “chrono-synchronized” products. Chrono-synchronized products cater to the skin according to the time of day. For example, they can draw on richer actives for nighttime repair and ingredients that strengthen the skin’s barrier for daytime use. 

“The peak time of epidermal cell division, the nadir of transepidermal water loss, the diurnal rhythm of UV-induced DNA damage response, and the nocturnal surge of skin repair enzymes — all of these represent windows of biological opportunity or vulnerability that modern therapeutics have failed to exploit systematically,” she says.

Working with skin time

Almost every living organism, from plants to insects to humans, runs on a roughly 24-hour internal clock that tells the body when to sleep, eat, wake up, and carry out survival tasks.

The scientific review found that the skin, as an organ, has its own internal clock run by specific genes that turn on and off in a daily rhythm. These genes control over 2,000 other skin genes, which all rise and fall in activity in a 24-hour cycle. 

The review notes that skin cells do not need signals from the brain to keep time, but rather run on their own. Skin cells like melanocytes and keratinocytes have built-in light sensors, which allow them to respond directly to sunlight exposure without any input from the eyes or brain.

Skin permeability and repair activity change throughout the day.Notably, the research underscores that there is wide variation in a consumer’s clock gene expression, and it can be influenced by age, sex, anatomical site, and a person’s chronotype. According to the review, a person’s chronotype is partly a biological trait — evening chronotypes have their internal clocks running later. 

Time-targeted innovation

The study findings open up formulation opportunities for the personal care industry. In the early evening, the skin’s junction proteins loosen, and moisture loss naturally increases, making the skin barrier more permeable at this time.

The author notes that formulators can draw on this process to create night creams with higher concentrations of retinoids, peptides, or DNA repair enzymes to maximize their penetration and effectiveness.

The research also found that, during daylight hours, the skin’s ability to repair UV damage and trigger protective cell death is at its lowest, making it more vulnerable to sun-induced harm. Formulators could prioritize antioxidants and stronger UV filters for morning formulations.

Confusing the clock

The research found that disrupting the skin’s natural rhythm according to its circadian clock can contribute to several skin conditions and disease progression, such as melanoma, eczema, and psoriasis.

Job shifts and jet lag, for example, can reduce the skin’s expression of protective clock genes, potentially increasing melanoma risk.

In atopic dermatitis, the review confirmed that itching worsens at night when the skin exhibits lower barrier function, and there is a coordinated pro-inflammatory shift. Psoriasis symptoms also showed clear daily and seasonal patterns.