Circadian rhythm
The importance of the circadian rhythm for the skin
It is scientifically well established that our bodies follow a circadian rhythm. The cycle follows the alternation of light and darkness in a 24-hour cycle and controls the body’s physiology. The central control center for the day/night cycle is located in the suprachiasmatic nucleus (SCN). This core area responds to light received via the retina and regulates sleep patterns, body temperature, heart activity, hormone release, blood pressure, and other bodily functions. The peripheral clocks of mammals, also known as clock genes (including period [per], clock [clk], cycle [cyc], timeless [tim]), were only recently discovered. They are present in all nucleated cells of the body. It is believed that 10-20% of our genes are under the direct circadian control of the central control center in the suprachiasmatic nucleus. These peripheral clocks synchronize important bodily functions with the day/night cycles to achieve well-regulated metabolic performance. They play an essential role in maintaining genome stability. Simply put:
The clock genes controlled by the SCN ensure that all cell functions take place at the right time and repeat themselves daily.
The well-coordinated symphony of tasks forms the basis for the functional integrity of living organisms by synchronizing them with natural rhythms at the cellular, organ, and tissue levels.
However, the synchronization of these body clocks with the natural circadian rhythm can be disrupted. This has dramatic consequences. Shift workers are more prone to obesity and other metabolic diseases. In young adults, elevated cortisol levels, a higher BMI (body mass index), and an increase in inflammatory mediators such as IL-6 and TNF-a have been detected.
The increased tendency to inflammation can increase the risk of cardiovascular disease. An increased incidence of breast cancer and prostate cancer has been observed in people who have worked shifts for a long time; the disruption of the circadian rhythm is an obvious risk factor here. Scientific research is increasingly confirming the link between circadian body rhythms and health.
The importance of this topic is also underlined by the 2017 Nobel Prize in Physiology or Medicine, which recognized work on elucidating the molecular mechanisms that control circadian rhythms. Precision medicine, which is based on the body clock, is still in its infancy, but is receiving increasing attention in the specialist literature with studies that tailor treatments, whether for allergies or cancer, to the time of day, thereby minimizing side effects.
Cosmetic ingredients for the circadian rhythm of the skin
As our largest organ, the skin occupies a special position between the environment and the inside of the body and forms the first protective barrier against harmful environmental influences.
Skin activities during the day
The diverse functions of the skin have been proven to follow a strict circadian rhythm. During the day, they are ramped up to provide greater protection, while at night they are geared towards repair and the breakdown of harmful residues.
The skin is a network of many millions of cells. Imagine the chaos if every single cell simply did what it wanted, when it wanted. Chaos would be inevitable!
Nature regulates with precise timing which function is to be performed at what time and ensures coordination between the cells in order to achieve the best possible performance in terms of protection, maintenance, repair, and regeneration of the skin. It is important to understand and protect these mechanisms, as they are fundamental to optimal skin condition.
When healthy and undamaged, the skin provides maximum protection during the day, while its repair functions run at full speed at night. Reports show that the skin is thicker and has a higher pH value during the day than at night. The production of sebum, which is necessary to keep the skin moist, is also most intense during the day.
Skin activity at night
Due to increased blood circulation, skin temperature is higher at night and the skin barrier is more permeable. This is accompanied by increased moisture loss, which is approximately 25% higher at night than in the morning.
At the cellular level, cell regeneration is lower during the day than at night. This means that the cells and their DNA are protected as well as possible from environmental damage, especially UV radiation. Measurements show that the rate of cell regeneration is about 30 times higher at night than at midday.
Autophagy and DNA repair are also more active at night. These close relationships between circadian rhythm, cell division, damage repair, and DNA repair protect the integrity of the genome and tissue homeostasis.
How can the rhythm get out of sync?
This precise clockwork can lose synchronization with the circadian rhythm for various reasons. Environmental influences such as UV radiation or air pollutants, travel to other time zones (jet lag), lack of sleep, stress, light pollution, and aging disrupt the synchronization of skin cells.
The consequences are reduced performance in terms of both protection during the day and repair at night.
It has been proven that these influences affect the clock genes, which in turn affects cell functions. Autophagy, energy, and collagen formation decrease, while ROS and inflammatory mediators increase. The latest scientific findings point to another harmful environmental influence: light pollution at night. It severely disrupts the circadian rhythm and must now be considered a skin aggressor. Since industrialization, we have increasingly used artificial light sources (light pollution) to extend working days and develop our modern lifestyle. Living in a 24/7 society has led to the elimination of evening/nighttime light reduction, thereby removing the signals that tell the body it is time to sleep.
The increase in light exposure at night is mainly due to the widespread use of LED light sources, TV screens, the explosive growth of electronic devices for private use, and smartphones, which emit intense blue light. The blue light of the sun is the strongest signal for our bodies to synchronize with the daily rhythm; it makes us alert and attentive, boosts memory and cognitive functions, and lifts our mood. However, when these artificial light sources are used at night, their high blue light content prevents the natural reduction in light that tells our bodies to switch to nighttime mode. The blue light “tricks” the body into behaving as if it were daytime. This disrupts the body’s natural rhythm, reduces melatonin secretion, causes poor sleep, and impairs memory and attention.
HEV (blue) light disrupts the circadian rhythm
Skin researchers have been conducting research in the field of circadian skin rhythms for over a decade. An important question was whether blue light at night also negatively affects circadian skin rhythms. Researchers developed a blue light chamber, exposed skin cells directly to an LED source, and recorded the damage to per-1 clock genes and skin cells. The results showed that skin cells are extremely sensitive to blue light exposure at night. This led to a reduction in the activity of per-1 clock genes, an increase in ROS and the formation of inflammatory cytokines, as well as increased DNA damage. The consequences are the desynchronization of skin functions and an increase in damage, which accelerate the visible aging process.
Numerous studies in our and other laboratories show how important it is to maintain the synchronization of skin cell functions with the circadian rhythm, as this keeps the skin healthy and looking younger. Just as precision medicine is paying greater attention to the timing of treatments and medication administration in relation to the body clock, skin care must also focus more on ensuring that skin protection or repair is specifically optimized with morning or evening application. Finally, it is important to identify the factors that disrupt and interfere with the perfect clockwork in order to prevent skin damage and premature aging. The better and faster we understand the finely tuned relationships of the circadian skin rhythm, the more effective and perfectly personalized skin care we can develop.
The following properties and functions of the skin change in sync with day and night:
DAY
Highest skin protection
Greatest skin thickness
Most intense sebum production
Highest pH value
Least cell regeneration
NIGHT
Strongest autophagy
Highest DNA repair rate
Most intensive cell regeneration
Highest skin temperature
Greatest barrier permeability
Strongest itching
Greatest moisture loss
Strongest skin blood circulation
Lowest barrier formation rate
We enjoy working with these active ingredients, which have a positive effect on the skin’s circadian rhythm:
| Trade name | NCI | Manufacturer | Comment |
|---|---|---|---|
| Chrono Chardy | Aqua (and) Butylene Glycol (and) Vitis Vinifera (Grape) Fruit Extract | Ichimaru Pharcos Co./Safic Alcan | |
| Chronogen YST biofunctional | Aqua (and) Glycerin (and) Hydrolyzed Yeast Protein | Ashland | |
| Varrier | Butylene Glycol (and) Water (and) Morus Nigra Fruit Extract (and) Lycium Chinense Fruit Extract (and) Fragaria Chiloensis (Strawberry) Fruit Extract (and) Berberis Vulgaris Root Extract | Clariant | |
| Sun Chronize | Glycerin, Aqua, Crocus Sativus Flower Extract | Berkem |
Cosmetics based on the concept of the skin’s circadian rhythm
Cosmacon is happy to develop premium products for you based on the concept of the skin’s circadian rhythm. The use of active ingredients with proven positive effects on the skin’s day and night rhythm makes your brand even more attractive to your customers. Please contact us if you are interested in such cosmetic products.
When products are needed quickly:
✨ Our partner Tojo Cosmetics offers innovative, active ingredient-rich private label products – quickly available, high quality and perfect for brands that want to impress with passion and quality.
Sources:
Tuft C, Matar E, Menczel Schrire Z, Grunstein RR, Yee BJ, Hoyos CM.Clin Interv Aging. 2023 Jan 12;18:49-59
Population-level rhythms in human skin with implications for circadian medicine.
Wu G, Ruben MD, Schmidt RE, Francey LJ, Smith DF, Anafi RC, Hughey JJ, Tasseff R, Sherrill JD, Oblong JE, Mills KJ, Hogenesch JB. Proc Natl Acad Sci U S A. 2018 Nov 27;115(48):12313-12318