Every organ in the human body operates on a natural 24-hour rhythm, and the skin is no exception. This natural internal timing system, known as the circadian rhythm, governs the way the skin reacts and regenerates throughout the day.
At Circadia, this natural rhythm is more than an inspiration for our products. Chronobiology is the scientific foundation on which our entire brand was built.
For over two decades, we have dedicated our resources to advancing circadian-rhythm based skincare science: the understanding that the skin’s needs shift in predictable cycles, requiring protective support during the day and reparative nourishment at night. This philosophy shapes every formula, every protocol, and every educational program we offer.
Understanding the Skin’s Circadian Rhythm
The word “circadian” comes from the Latin circa diem, meaning “around the day.” It describes the biological cycles that repeat approximately every 24 hours and are regulated by internal clocks located throughout the body.
The skin contains its own collection of these clocks, embedded in cells such as keratinocytes, fibroblasts, melanocytes, and immune cells. These cellular clocks coordinate essential processes including DNA repair, cell division, barrier recovery, and immune defense.
Circadia: The Pioneer of Circadian Skincare Science
Circadia is widely recognized as the pioneer of circadian rhythm–based skincare science, with chronobiology serving as the foundational framework for the original research and formulation strategy from the outset.
The science that explores these rhythms, also known as chronobiology, is the heart of the Circadia brand. Our founder, Dr. Peter T. Pugliese was considered an early leader in this approach. He was among the first researchers to examine the role of circadian rhythms in skin physiology and how working with the natural timing of the skin accelerates positive treatment results.
Today, under the leadership of Michael Q. Pugliese, this research continues to evolve so that we can continue to advance both professional education and product innovation across the industry.
Daytime: The Skin Needs Defense
As the largest organ in the human body, the skin serves as the first line of defense from harmful bacteria, toxins, and injury. Nurturing and nourishing the skin is essential to the body’s ability to fight disease, reinforcing its role as both a physical shield from harm, but also as a complex micro-ecosystem that requires a deep understanding.
During the day, the skin’s cells have the primary responsibility of protection. The skin is constantly exposed to the sun (ultraviolet radiation), blue light, environmental stressors, and temperature fluctuations. All of these things can contribute to premature aging, inflammation, disease, and in extreme cases–death.
In order to maintain a healthy microbiome and homeostasis, the skin needs to be able to withstand those stressors, or at the very least be supported in combating their effects.
During the day, the skin naturally increases antioxidant activity, strengthens the barrier, regulates sebum production (how much oil the skin generates), and heightens immune vigilance.
Due to modern day environment stressors, the oxidative load often exceeds the skin’s natural antioxidant capacity, which is why topical antioxidants are so beneficial.
Since the skin is focused solely on defense during daylight hours, it benefits most from ingredients designed to support these natural protective mechanisms. Daytime skincare should aid in protection, shield the skin from free-radical damage, reinforce the healthy barrier, and prevent moisture loss.
Circadia’s formulation philosophy for daytime products aligns with this biological reality by strategically incorporating antioxidants, pollution protectors, and barrier-supportive ingredients that help the skin remain resilient under stress.
Nighttime: The Skin Shifts Into Repair Mode
As the day winds down, the skin follows the same circadian signaling patterns as the brain, muscles and other tissues, transitioning from a defensive state into a regenerative phase. While the skin may appear quiet at the surface, cellular activity increases significantly once sleep begins and cells transition into regenerative phases.
During nighttime hours, keratinocyte proliferation accelerates, cellular turnover increases, and DNA damage from the day upregulates. This is the time when the body can focus on repairing and renewing. As microcirculation improves, allowing ingredients to penetrate more effectively, what you put on your skin before bed is critical in aiding recovery.
Cortisol levels also lower during sleep, causing transepidermal water loss (TEWL) to naturally increase. Without adequate hydration, TEWL can result in overnight moisture loss, impaired barrier recovery, and heightened daytime sensitivity. This circadian-driven rise in permeability also supports cellular repair, lipid synthesis, and enhanced ingredient absorption.
Nighttime skincare formulation should focus on three core functions. Replenishing hydration, reinforcing barrier lipids and supporting barrier repair.
Humectants such as glycerin, hyaluronic acid, sodium PCA and beta-glucan can attract and bind water within the epidermis, counteracting TEWL. Chronobiology-aligned actives like Vitamin A, niacinamide, peptides, antioxidants, and stem cells work synergistically with nighttime repair pathways to promote healthier skin.
Circadia’s evening formulations focus on peptides, stem cell technologies, and nutrient-rich moisturizers that enhance renewal, encourage accelerated natural repair, and optimize hydration while the body sleeps. In essence, nighttime is the ideal window to address aging, texture, dullness, and other concerns that benefit from intensive correction.
The Impact of Circadian Disruption on Skin Health
Modern lifestyles often disrupt the body’s natural rhythms. Irregular sleep patterns, blue-light and screen exposure late into the evening, daily stress, and travel can all interfere with normal circadian function. When these rhythms fall out of sync, the skin’s ability to protect and repair itself becomes compromised.
Visible consequences of circadian disruption may include heightened skin sensitivity, increased inflammation, greater transepidermal water loss, delayed healing, and premature signs of aging such as wrinkles and uneven skin tone. Circadian rhythm based skincare helps restore balance, resilience, and optimal function by working with the skin’s natural timing rather than against it.
Formulating in Harmony With the Skin’s Natural Timing
Circadia’s formulations reflect a deep respect for the skin’s dynamic needs. During the day, our products focus on protecting the skin from oxidative damage, environmental stress, and dehydration. At night, our formulas support regeneration with peptides, advanced stem cell technologies, and restorative moisturizers that complement the skin’s increased repair activity and increase cell turnover.
This rhythmic approach ensures that the skin receives the right ingredients at the right time, maximizing effectiveness and enhancing both immediate and long-term results.
Why Circadian Rhythm Based Skincare Matters
Circadian rhythm based skincare matters because timing is one of the most powerful variables in skin health. When products and treatments are aligned with the skin’s natural biological cycles, the skin performs at its highest potential. Ingredients absorb more effectively, cellular processes operate more efficiently, and the visible results become more profound.
Circadia believes that skincare should honor the body’s innate wisdom and natural functions. Our mission is to improve and inform both professional practice and everyday routines through science-based solutions that support the natural circadian rhythms of the skin.
This is the rhythm of true skin health, the science that has guided our brand since day one, and the promise we continue to deliver to professionals and consumers worldwide. This is the essence of circadian rhythm based skincare, and it is the guiding principle for everything we do at Circadia.