You’ve probably heard of circadian rhythm before, but chances are you associate it more with sleep patterns than with your skin. Circadian rhythms are physical, mental, and behavioral changes that follow a 24-hour cycle. Your body is constantly making adjustments based on the time of day. These adjustments are triggered by both your biological or “internal” clock and by external environmental signals.
The main environmental signal that dictates our circadian rhythms is light. This signal is picked up through the eyes and transferred to different organs. Other signals include things like temperature, exercise, and food (this is why you might’ve heard that it’s best to avoid eating late at night).
Many organs are thought to have their own circadian rhythm, and skin is no exception.
Why Does Understanding the Skin’s Circadian Rhythm Matter?
I’ve always told my clients and customers that when it comes to treating skin, you have to work with Mother Nature and not against her. For example, the fastest way to get rid of a blemish is by working in sync with its natural life cycle. Using the right type of spot treatment with the right ingredients at the right time makes all the difference in the world and is key to getting rid of a blemish quickly.
Circadian rhythm is a similar concept. By using the right skincare ingredients at the right time of day, you can optimize your skincare routine and give your skin exactly the type of support it needs for better results.
What Your Skin is Doing During the Day
During daylight hours, your skin is constantly exposed to aggressors like UV radiation, pollution, and free radicals, all of which can cause DNA damage. This means that during the day, your skin is protecting itself. You want to do everything you can to support its natural defenses.
These are a few of the physiological changes that take place in your skin during the day:
- Lower Temperature: The surface temperature of your skin is lowest early in the day. Your skin gets a lot of heat exposure from the sun, though, which can increase inflammation, redness, and pigmentation.
- Increased Sebum Production: Your skin’s production of sebum (oil) peaks in the early afternoon. This is basically your skin creating a natural film to protect itself from the environment (and the reason you may sometimes feel your skin is an oil slick by the end of the day).
- Better Moisture Barrier Function: Studies suggest your skin is better at holding on to moisture during the day thanks to improved barrier function. This results in better moisture retention but also means your skin is less receptive to skincare products.
- Increased Antioxidant Production: Your skin’s natural antioxidant production is increased during the day as it tries to protect itself from DNA damage caused by free radical molecules.
Best Skincare Ingredients for Daytime
With this in mind, here are the best skincare products to use in the morning. All of these boost your skin’s natural defense mechanisms.
No surprise here! A sunscreen with SPF 30 or higher is the most important step in your morning routine. It’s also the number one way to protect your skin against DNA damage from harmful UV rays. We already know sunscreen is important for preventing premature skin aging and skin cancer, but it seems there’s another reason to use it faithfully. Some studies have shown that UV radiation can disrupt your skin’s circadian rhythm for up to 24 hours. This means too much sun exposure could interfere with your skin’s nighttime repair processes. It illustrates the importance of protecting your skin with both SPF and sun-protective clothing.
This is a great example of supplementing your skin’s natural defenses. Your skin is already working hard to produce antioxidants during the day, but adding more topically is a great way to give it a boost. Antioxidants help prevent skin damage on a cellular level by running interference against unstable free radical molecules.
Yes, you read that right! I believe wearing some form of foundation makeup every day is a great way to give your skin extra protection. Here’s how it works.
For more detail, learn how to put together the perfect morning skincare routine.
What Your Skin is Doing at Night
If daytime is all about defense, nighttime is all about offense. This is when your skin gets to work repairing any damage that has been incurred throughout the day. Even though your skin is constantly working to repair itself, these processes definitely peak in the evening (they don’t call it “beauty sleep” for nothing!). These are a few of the physiological changes taking place in your skin at night:
- More Permeable Barrier: Now that your skin is not facing an onslaught of environmental aggressors, your skin’s protective barrier function is reduced. This means two things: 1) Your skin is more receptive to products, so you want to take advantage by adding a serum to your nighttime routine. 2) It’s super important to use a well-formulated moisturizer for your skin type to prevent water loss and support your skin’s moisture barrier.
- Higher Cell Proliferation: At night, your cells are growing and dividing at a higher rate so they can regenerate.
- DNA Repair & Renewal: Your skin gets to work repairing DNA damage from the day. This also helps bolster and strengthen your skin’s immune system.
Best Skincare Ingredients for Nighttime
With this in mind, here are the best skincare products to use at night. All of these boost your skin’s natural reparative processes.
During the day, your skin uses up its antioxidant supply to defend against free radicals. Applying antioxidants topically at night means your skin can use them for repair instead. Here are five of my favorite antioxidant ingredients to look for.
Retinol, or vitamin A, is technically also an antioxidant. It boosts skin cell turnover, which helps the skin to regenerate itself from within.
3. Exfoliating Acids
Exfoliating acids like AHAs and BHAs dissolve dead cells on the surface of your skin. These dead cells can make your skin look dull and may make it difficult for other active ingredients to penetrate effectively. Acids also help reduce unwanted pigment and encourage more even-toned complexion.
Peptides help build and repair collagen that’s been damaged by environmental aggressors. Collagen loss is a key component of skin aging, so peptides are a great (and generally well-tolerated) ingredient to look into.
Read more about how to build the perfect nighttime skincare routine.
What’s the Best Time to Do Your Nighttime Skincare Routine?
We used to think that repair processes only occurred at night during sleep. We now know that these processes actually kick in as soon as the sun starts to go down. Because your skin has its own circadian rhythm, the loss of daylight signals that it’s time to start moving into repair mode, even if you haven’t gone to bed yet. This may mean that it’s beneficial to do your nighttime skincare routine earlier in the evening rather than waiting until right before your head hits the pillow. Another reason I encourage this is that there’s less of a chance you’ll get too tired to do your nighttime routine and end up skipping it altogether.
Can Blue Light Affect Your Skin’s Circadian Rhythm?
Since the main signal governing our skin’s circadian rhythm is light, it stands to reason that blue light could have an effect. As I mentioned, it’s already been pretty well established that UV light has a big effect on these natural rhythms. Blue light is part of the visible light spectrum, which is emitted by the sun but also by our electronic screens.
While blue light given off by screens hasn’t really been implicated in skin aging, circadian rhythm may be another story. Truthfully, there’s a lot more research that needs to be done in this area before we can say for sure, but I don’t believe there’s a strong possibility of late-night screen time can interfere with the skin’s natural cycles. And since a disrupted circadian rhythm can interfere with everything from the skin’s immune system to DNA repair, it’s definitely worth considering. We already know it’s better for your sleep habits overall to avoid screens right before bed, so if it can improve your skin as well, even better!
What did you think of this topic? I think circadian rhythms are fascinating and that there’s still a lot of potential yet to be harnessed in this field. I’m excited to see more research in this area and hope it will help provide even more insight into how we can optimize and personalize our skincare routines!
Up next, read 10 nighttime skincare tips that can make a big difference.
Celebrity Aesthetic & Skincare Expert
As an aesthetic trained in cosmetic chemistry, Renée Rouleau has spent 30 years researching skin, educating her audience, and building an award-winning line of products. Trusted by celebrities, editors, bloggers, and skincare obsessives around the globe, her vast real-world knowledge and constant research are why Marie Claire calls her “the most passionate skin practitioner we know.”