When you’re sleeping, your skin is decidedly *not* at rest. Instead, it’s hard at work repairing and recovering from the damage incurred throughout the day, be it from sun exposure, pollution, or plain old stress. It’s your circadian rhythm at work.

But that eight or so hours of sleep is also a good opportunity to put your skincare products to work, allowing them to fully sink in and do their thing without any interruption. Plus, ingredients that cause sun-sensitivity or are prone to breaking down are similarly better applied at night, since there’s no risk of sun exposure interfering with their benefits. Here’s a rundown of the skincare products you should be wearing overnight — and why that timing is so important.

Sleep mask

Think of your overnight mask as a night cream, but with extra perks. For one, they tend to be more targeted. ”Sleep masks often have efficacious levels of ingredients to target specific skin concerns,” explains NakedPoppy research scientist Marisa Plescia. “Night creams are generally more designed for hydration and moisturization.”

Not only that, but they’re also created a little differently. “Sleep masks are formulated to not absorb as quickly into the upper layers of the skin and work over a longer period of time, a.k.a. overnight,” Plescia says. “They more or less ‘seal’ in the ingredients to work.” Try applying the KYPRIS Cerulean Mask before bed; it offsets the effects of stress on skin with soothing marine botanicals.

Retinol

Retinol, a form of vitamin A, is one of those ingredients that most can and should use — mostly because it’s jam-packed with benefits for a wide range of skin concerns, be it acne or fine lines. Plus, says Plescia, there’s ample research to back that up. “Retinol increases skin cellular turnover. Not only does this minimize the appearance of wrinkles by providing a fresher, healthier, and smoother layer of skin, but it also allows for the skin to be able to better respond to the damage caused by UV radiation,” she explains. “Expedited cell turnover can also help with hyperpigmentation and also prevent dead skin cells from clogging pores, thus reducing acne outbreaks.”

It’s best used at night for a few reasons. First, sunlight can break down retinol, reducing its efficacy. Overnight use “provides the retinol the opportunity to effectively work and be active without the potential of UV light breaking them down,” says Plescia. Then, there’s the issue of side effects, as retinol can cause redness and irritation in newbies. That’s where nighttime use can be strategic. “Using retinol at night will allow for your skin to calm down by morning,” she says. Try Maya Chia The Straight A Serum – Advanced Gentle Retinol Treatment.

Alpha hydroxy acids

For the uninitiated, alpha hydroxy acids, or AHAs, are a type of chemical exfoliant that count glycolic and lactic acids among them. “As opposed to physical exfoliation, which uses the mechanical action from rubbing with small particles, AHAs help dissolve the bonds between the skin cells, allowing for shedding of the dead skin cells,” says Plescia. “AHAs are powerful ingredients to add into your routine, and have been shown to help diminish the appearance of fine lines and wrinkles and improve skin’s firmness.”

AHAs are ideal at night for two reasons. “They can be irritating and can cause redness, tingling, and sensitivity — but if used at night, this potential inflammation should subside by morning and you will wake up with glowing skin,” says Plescia.

Secondly, if you do experience any redness or tingling, sun exposure will only make it worse — which is why AHAs aren’t advisable before you head outdoors. Your snooze time offers the perfect buffer between them. You can find lactic acid in. Skin a little sensitive? Try fruit enzymes instead, as they only target the superficial dead skin cells and are thus even more gentle than AHAs. KYPRIS Moonlight Catalyst Face Serum pairs them with nourishing botanicals.

Face oil

A good face oil can basically max out your skin’s natural nighttime repair. “Face oils can deliver a variety of skin nutrients to the skin, such as vitamins, minerals, and essential fatty acids to help moisturize the skin,” says Plescia. “They also have strong antioxidants working to help protect your skin from oxidative stress and damage caused by environmental factors, such as UV radiation and pollution.” That’s the case with NakedPoppy Revitalize Organic Facial Oil, which nurtures skin with a blend of rosehip seed, jojoba, and argan oils.

Another reason oils are ideal at night? That’s when your skin barrier is at its most permeable — meaning water in your skin can evaporate at a higher rate during the day. (It’s, again, just circadian rhythm doing its thing.) “Skin’s lipid matrix works to prevent excessive skin water loss and helps protect the body from environmental compounds,” says Plescia. “Since face oils are classified as lipids, they have the ability to improve the lipid barrier function.” Ultimately, they help keep water trapped in skin overnight.

While oils can certainly be used morning and night, some can feel a little heavy for daytime, depending on your skin type. “It may not be ideal and it may be difficult to apply makeup after,” says Plescia. “Using a face oil at night also really allows for it to remain on the skin, absorb into the upper layers of the skin, and lock in that moisturization.”

Consider it proof that getting the most out of your overnight hours is, like most things in life, all about good timing.

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