Your skin is affected by your circadian rhythm, or ‘body clock’, and goes through various changes over a 24-hour period that allow it to repair and protect itself.

These changes include variations in:

Water loss
Skin cell turnover and renewal
Blood flow
Skin temperature

Using the right skincare ingredients at the right time of day can help your skin through these natural variations.

Here’s how your skin changes over 24 hours, PLUS, 7 ways to use these changes to your advantage…

Table of Contents

How Your Skin Changes Over 24 hours

DNA Damage

During the day, your skin is exposed to UV radiation and environmental pollutants that can lead to premature aging, skin cancer, and inflammatory skin conditions.

Sun exposure, alone, continues to damage the DNA in your skin cells for up to 3 hours after exposure.

DNA Repair

Most DNA repair happens at night when your body naturally produces more human growth hormone (HGH). HGH helps your skin to repair itself as well as increasing the production of new skin cells.

Skin Cell Renewal

The rate at which your skin cells renew themselves is higher at night with the highest rate of renewal at midnight.

Oil Production

Your oil glands are a lot more active during the day, with activity peaking around midday and then declining until 4am when oil production is at its lowest.

If you have oily skin, you may find that your skin is particularly greasy in the middle of the day.

Skin pH

Your skin pH is at its most alkaline at 8am and its most acidic at 4pm.

As your skin’s natural pH is slightly acidic and a more alkaline skin is associated with irritation and inflammatory skin conditions, you may find that your skin is more sensitive in the morning.

Skin Temperature

Your skin temperature hits its peak in the afternoon and then dips at night.

Some skin conditions, like psoriasis, have been associated with thermoregulation (temperature control) problems which may also lead to difficulty fallings asleep at night and disruptions to your circadian rhythm.

Skincare Ingredient Penetration

Both water-loving and oil-loving skincare ingredients are able to penetrate your skin more easily in the evening than during the day, peaking at 4am then reducing through daylight hours.

This means that your skincare products will be more effective but, in the case of ingredients like chemical exfoliants, may cause more irritation.

Skin Permeability

Your skin’s permeability (how easily things can pass in and out) is higher in the evening than it is in the morning. While this means that your skincare products will be more effective, it also means that your skin will lose more water and is more likely to be inflamed overnight.

It’s one of the main reasons that eczema is usually itchier at night.

Blood Flow

The blood flow to your skin increases in the late afternoon and at night which brings more oxygen to your skin cells and increases clearance of substances like free radicals that have built up during the day.

This increased blood flow has been shown to help topical medications pass through your skin and diffuse into your blood stream.

Another reason why skincare products are more effective at night.

Is Beauty Sleep A Real Thing?

Beauty sleep (meaning an improvement in appearance resulting from sleep) sounds like an old maids tale but it’s actually a real thing!

Melatonin, the sleep hormone, increases in the evening which leads to a whole host of benefits for your skin:

It acts as an antioxidant
It reduces inflammation
It’s anti-aging
It improves wound healing
It helps skin conditions like eczema

Overview:

AM:

Your skin experiences the most damage during the day thanks to UV radiation from the sun and other pollutants from your environment.
Your oil glands are more active
Your skin temperature is higher
Your skin pH is at its most alkaline at 8am and its most acidic at 4pm

PM:

Your skin is more permeable
Your skin loses more water
You experience increased inflammation
Blood flow to your skin increases
Water-loving and oil-loving skincare ingredients are able to penetrate your skin more easily
The rate at which your skin cells renew themselves increases
Your oil glands are less active
Your skin temperature is lower
Your skin cells repair any DNA damage from the sun.
Melatonin (acts as an antioxidant) is higher at night

7 Ways To Use These Changes To Your Advantage:

Wear sunscreen! It protects your skin from UV radiation which is responsible for up to 90% of skin aging.
Use antioxidants alongside sunscreen as they work synergistically with sunscreen to protect your skin against UV radiation. They also protect your skin from the effects of pollution.
Use acidic products (e.g. salicylic acid cleanser, ascorbic acid, etc.) in the morning to keep your skin pH at its acidic ideal. Ascorbic acid (vitamin C) is also an excellent antioxidant. Note: salicylic acid has been shown to protect skin from UV radiation (unlike glycolic acid/AHAs) but it is not a replacement for sunscreen).
Use oil-controlling products in the AM – ingredients like salicylic acid, niacinamide, and green tea can help reduce oil production and help control midday oiliness. The latter two are also antioxidants which means they help with #2 as well!
Use DNA-repairing enzymes (e.g. photolyase found in bacteria and plants) to help your skin undo the damage done during the day.
Enhance your elevated rate of skin cell renewal by using retinoids (e.g. retinol) at night.
Use heavier moisturizers at night to reduce the amount of water lost from your skin overnight. Dry skin may benefit from an occlusive moisturizer to really lock in moisture.

Products That Contain DNA Repair Enzymes:

Priori DNA Intense Recovery Cream

Neova Total Repair Serum (affiliate link)

Elizabeth Arden RX Triple Protection Factor Broad Spectrum SPF 50+

You can also look for products that contain ‘plankton extract’ as this is a good source of photolyases.

Summary

Your skin has its own circadian rhythm and goes through a variety of changes in a 24 hour period.

Tweaking your skincare routine to enhance your skin’s natural biological processes can help to keep your skin healthy and nourished.

In the AM, your focus should be on protecting your skin with sunscreen and antioxidants. You can use antioxidants at night too but they’re better at preventing damage than at repairing it.

You don’t have to stick to one antioxidant either because they all complement each other’s effects (the best example being vitamin C, E, and ferulic acid).

In the PM, you should stick with products that enhance your skin’s natural repair process (e.g. retinol and DNA repairing enzymes) and products that lock moisture into your skin (e.g. heavier moisturizers, occlusives).

7 Ways To Enhance Your Skin’s Natural AM vs PM Processes (Skin Circadian Rhythm)