You don't need us to tell you how important sleep is for your mental and physical health—just one restless night will make that glaringly obvious. But adequate rest is also vital for your skin's well-being. In addition to emphasizing dark circles and puffy-looking eyes, sleep deprivation can make your skin appear duller and less youthful. Of course, getting a solid eight hours every night isn't always possible. Investing in a nighttime skincare routine—and in particular, an effective night serum—can help keep your skin looking its consistent best regardless of how many hours of shut-eye you get.

Ahead, we'll delve into the basics of night serums and what they can do for your skin. Like daytime formulas, a night face serum can help address skin concerns and promote a more radiant appearance, but it's important to choose a formula that suits your individual needs. For this reason, we'll also provide recommendations on the best Kiehl's serums to add to your nighttime skincare routine. Keep reading to learn how to use a night serum for hydrated, healthy-looking skin.

Why You Need a Nighttime Skincare Routine

Before we dive into the benefits of night serums, we thought it'd be helpful to review what happens to your skin when you sleep. Sleep is essentially your body's built-in maintenance system. While you snooze, your brain releases several essential hormones that help regulate cell growth and renewal. It also works to find and eliminate toxins that accumulate throughout the day, often in response to external stressors like pollution and sun exposure. Not getting enough sleep interrupts these essential processes, making your entire body (skin included) vulnerable to damage. Studies show that insufficient sleep is associated with a loss of skin elasticity, inflammation, and impaired skin barrier function.I Ultimately, this can result in dehydrated skin, uneven skin texture, and the early development of age-related skin concerns, like fine lines and wrinkles.

Of course, the only way to prevent the effects of sleep deprivation is to, well, sleep. But, a proper nighttime skincare routine can help supplement your sleep and hydrate and nourish your skin so you wake up looking your best. The right products can also help reduce visible signs of poor sleep, like fine lines, and promote a more lively, healthier-looking appearance. Though your specific skincare routine should be tailored to your unique skin type and needs, every nighttime routine should include at least four key products: a cleanser, a moisturizer, an eye cream, and perhaps most importantly, an effective night serum.

What Is a Night Serum?

In order to explain the benefits of a night serum, you need to first understand the value of using any face serum at all. Serums are a liquid skincare treatment that you apply to your face after cleansing and before moisturizing. They're primarily designed to help address visible skin concerns and typically contain high concentrations of active ingredients to help improve your skin's overall appearance. Because these formulas help directly address skin concerns, they're a key part of any effective skincare routine. And they're especially beneficial for nighttime use because that's when your skin repairs itself, as we described above. This is the reason for the popularity of night serums.

Nighttime serums can refer to formulas suited for day and night application as well as those intended solely for overnight use. They're often made to work in harmony with your body's natural overnight repair processes and may contain hydrating ingredients, antioxidants, oils, or mild acids to help refine your skin for a refreshed, healthy-looking appearance come daybreak.

Our Best Night Serums To Add To Your Routine

Now that you're caught up on what a night serum is—and why it's a vital part of an effective nighttime skincare routine—you can go ahead and start looking for a formula that suits your needs. Keep reading to discover the best Kiehl's night serums for your skin type and concerns.

The Formula: Clearly Corrective Dark Spot Solution

What It Does: If dark spots and discolorations are your primary skin concern, we recommend reaching for Clearly Corrective Dark Spot Solution, which is formulated with stabilized vitamin C, salicylic acid, and peony extract. This brightening face serum is clinically-demonstrated to help diminish both the number and intensity of dark spots, such as those caused by age or post-inflammatory hyperpigmentation (also known as post-acne marks).* It's suitable for all skin types and has been tested on a wide range of skin tones. Use it as a spot treatment for individual dark spots, or apply several drops to clean skin before your nighttime moisturizer for visibly more even, radiant-looking skin.

*This product was tested on a multi-ethnic panel equally distributed: 25% African-American, 25% Asian, 25% Hispanic, 25% Caucasian. Results based upon a clinical study of the upper layers of the skin.

The Formula: Clearly Corrective Accelerated Clarity Renewing Ampoules

What It Does: For a more targeted dark spot treatment, try Clearly Corrective Accelerated Clarity Renewing Ampoules. This two-week intensive program contains 28 single-use ampoules formulated with activated C (a form of stabilized vitamin C) and a blend of chemical exfoliants, including lactic, phytic, and glycolic acids. When used morning and night for 14 consecutive days, the effective treatment is clinically-demonstrated to improve skin's radiance.* It also promotes accelerated cell renewal for smoother, more even-looking skin.

In the morning, apply one ampoule to clean, dry skin and top with moisturizer and sunscreen. You can also layer the ampoule with Clearly Corrective Dark Spot Solution for an added boost in the a.m. and p.m. The treatment is suitable for all skin types and can be used as needed for visibly brighter skin.

*In a clinical test.

The Formula: Hydro-Plumping Re-Texturizing Serum Concentrate

What It Does: Everyone's skin needs adequate hydration in order to look and feel its best. In addition to drinking plenty of water, try incorporating a hydrating serum into your nighttime skincare routine to help keep your skin visibly plump and well-moisturized. We recommend Hydro-Plumping Re-Texturizing Serum Concentrate, which contains glycerin and our unique epidermal hydration filler. The lightweight formula for all skin types helps encourage skin's natural production of hyaluronic acid, an essential molecule involved with maintaining skin hydration. It also helps diminish the appearance of dullness and boosts skin's elasticity for visibly smoother, more hydrated-looking skin around your eyes and on your entire face. To really pamper your skin, store it in the fridge for a cooling effect.

Kiehl's Expert Tip: Pair your nighttime serum with an overnight face mask for added hydration. Learn more in our article Why You Need An Overnight Face Mask.

The Formula: Vital Skin-Strengthening Hyaluronic Acid Super Serum

What It Does: As your first line of defense between yourself and the rest of the world, your skin's natural moisture barrier is constantly exposed to environmental aggressors that can damage your skin's appearance. Keeping your skin barrier strong is therefore crucial for balanced, healthy-looking skin. To help strengthen this natural barrier, add Vital Skin-Strengthening Hyaluronic Acid Super Serum to your nightly skincare routine.

This potent serum for daytime and nighttime use is formulated with 11kDa hyaluronic acid, an engineered form of hyaluronic acid capable of penetrating skin's deeper layers (8 layers deep, to be exact). It also contains a blend of adaptogenic herbs, including red ginseng. The formula is clinically-demonstrated to double skin's strength while helping improve the appearance of uneven skin tone and texture.* With continued use, it helps minimize the look of fine lines and wrinkles and boosts skin's resiliency for a more radiant appearance. Apply the fast-absorbing formula to clean, dry skin every night, then top with moisturizer for glowing, youthful-looking skin.

*Based on a four-week clinical study of 58 subjects tested in urban and polluted environments. Based on skin strength index = A composite average score of skin plumpness, suppleness, and resiliency.

The Formula: Midnight Recovery Concentrate Face Oil

What it Does: Midnight Recovery Concentrate Face Oil may not be a serum, but we'd be remiss not to mention it in a conversation about the best nighttime products. It's a night oil that boosts essential moisture to help restore the appearance of tired-looking skin. The formula with evening primrose oil, lavender essential oil, and squalane replenishes skin at night for radiant, younger-looking skin by morning. After applying any of the above night face serums, top it with our oil to elevate your routine.

Next: How To Help Dry Skin Overnight