As skincare experts, we’re constantly fielding questions from customers about skincare products and ingredients. People often want to know which ingredients or formulas are best for their skin type or what to use to help correct skin concerns like premature aging. One question we’ve heard time and time again is: “What is serum, and how does it differ from face oil?” It’s a great question and one a lot of people have. Admittedly, face serums and oils are similar in many ways. For instance, they’re both liquid skincare products designed to help improve skin texture and appearance. But they’re also different in many ways—and understanding how they both work is vital to using them properly.

To help, we’ve put together a guide to the differences between serum and oil. Ahead, you’ll learn about the benefits and uses of both, and how to use facial oil and serum in your routine, separately and together. We’ll also provide recommendations on our best facial serums and oils to use for your skin type and concerns. Read on for everything you need to know about how face serums and oils differ.

What Is Serum?

When people ask us “what is serum,” what they usually mean is “what does serum do?” The answer to this question varies depending on the formula. However, serums can broadly be defined as light, concentrated liquids designed to help address visible skin concerns, such as uneven skin tone or texture. They’re typically water-based and often contain lightweight moisturizing ingredients, like hyaluronic acid. Their thinner texture and fluid consistency allow serums to penetrate the skin quickly and easily, making them suitable for use morning and night.

How Should You Use Face Serums?

Since serums have a lighter texture, they’re usually applied fairly early in your routine—typically after cleansing and toning, but before moisturizer or sunscreen. You’ll want to apply enough to cover your face in a thin layer (a pea-sized amount usually suffices).

At Kiehl’s, we have a range of different serums to choose from, such as our customer-favorite Powerful-Strength Vitamin C Serum. Made with 12.5% vitamin C and hyaluronic acid, this concentrated facial serum boosts radiance and helps firm the skin. With consistent use, it helps visibly diminish fine lines and wrinkles and minimizes the appearance of large pores, leaving the skin smoother-looking. The gentle formula is suitable for all skin types and can be used morning and night as part of your regular skincare routine.

Another great option for all skin types is our Vital Skin-Strengthening Hyaluronic Acid Super Serum. This fast-absorbing serum is made with 11kDa hyaluronic acid, an engineered form of hyaluronic acid capable of penetrating skin’s deeper layers. The powerful yet gentle formula is clinically-demonstrated to double skin’s strength and helps it resist the effects of damaging external stressors, like air pollution.* It also helps visibly improve skin’s texture and boosts radiance for a more glowing, youthful appearance over time.

*Based on a 4-week clinical study on 58 subjects tested in urban and polluted environments. Strength Index = Composite, average score of clinically graded parameters after using the product for 4 weeks vs one week of use.

What Is Face Oil?

As you can probably guess, facial oils are oil-based liquid skincare products designed to be used on the face. They’re typically formulated with non-comedogenic botanical oils and essential oils (non-comedogenic means they don’t clog pores). Facial oils often also include plant extracts and antioxidants. These rich, emollient formulas can help moisturize and soften the skin, nourish the skin’s natural moisture barrier, and help address some skin concerns, like dryness or dullness.

How Should You Use Facial Oils?

Generally speaking, we recommend using facial oils at the end of your skincare routine because they can act as an occlusive, trapping in moisture and helping to prevent water loss. You don’t need to use much—two to three drops are usually sufficient—and you can pat it over your entire face or apply it only to dry areas to give your skin a natural-looking, dewy glow.

If you’re new to oils, we recommend starting with a lightweight facial oil serum, like Daily Reviving Concentrate. The antioxidant-rich formula with sunflower oil and tamanu oil revitalizes the skin and helps correct the visible signs of fatigue. It’s also non-comedogenic and non-acnegenic, suitable for all skin types, and can be used daily. Pat a few drops onto your face at the end of your morning skincare routine for fresh, healthy-looking skin.

Should You Apply Serum or Oil First?

First things first: You can use face oil and serum together—it’s not an either/or type of situation. As a rule of thumb, we typically recommend applying products in order from lightest to heaviest. For oils and serums, that usually means applying serums (which are often water-based) first. After the serum absorbs, you can apply your moisturizer, then top it off by patting a few drops of facial oil onto your skin.

If you want to use both a serum and facial oil, but not simultaneously, try breaking it up. Designate one formula for your morning routine and the other for your nighttime routine. If you’re doing this, we’d recommend reaching for the serum for daytime since it’s typically lighter in texture and won’t weigh down your skin. Then, apply a richer oil at night to nourish your skin.

Face Oil vs. Serum: Which Is Right For You?

While you can layer oil and serum, it’s not a necessity. Ultimately, which formulas you use—and when—depends largely on your personal preferences, skin type, and goals. That said, there are some skin concerns for which oils may be more beneficial and vice versa. Read on to discover which formulas we recommend for your skin type and how to use them for healthier-looking skin.

Visible Aging:

Micro-Dose Anti-Aging Retinol Serum with Ceramides and Peptide

Address the visible signs of aging with Micro-Dose Anti-Aging Retinol Serum with Ceramides and Peptide. The potent serum, which contains a micro-dose of pure retinol, helps encourage gentle skin surface turnover to reveal more youthful-looking skin. It’s clinically-demonstrated to help reduce wrinkles and firm the skin and delivers visible anti-aging results with minimal dryness, redness, or peeling.* Over time, it also helps refine skin texture, even the skin tone, and visibly reduces the appearance of enlarged pores. The efficacious formula is suitable for all skin types (retinol newbies included) and can be used daily as part of your anti-aging skincare routine.

*Results based on expert grading in a clinical test for subjects showing improvement after 12 weeks of use.

Uneven Skin Tone:

Clearly Corrective Dark Spot Corrector

Environmental aggressors, age, and even breakouts can all contribute to dark spots and discolorations, which can give the skin an uneven appearance. To help even out your skin tone and improve the appearance of skin discolorations, incorporate Clearly Corrective Dark Spot Corrector into your daily skincare routine. The potent serum with activated vitamin C and buffered salicylic acid helps improve the appearance of a wide array of dark spots, including those caused by age and ultraviolet radiation. It also helps boost radiance and visibly brightens the skin over time. The dermatologist-tested formula is suitable for all skin types, and it can be used daily on your face as well as on your neck, hands, and decolletage.

Problem Skin:

Cannabis Sativa Seed Oil Herbal Concentrate Face Oil

It may, at first consideration, seem counterintuitive to use a facial oil to help manage problem skin since blemishes are often linked to overly oily skin. But drying out your skin isn’t the answer to your skin struggles. In fact, using non-comedogenic face oils, such as Cannabis Sativa Seed Oil Herbal Concentrate Face Oil, can be hugely beneficial when it comes to managing problem skin. This effective facial oil is formulated with 100% naturally-derived ingredients, including Cannabis sativa seed oil and green oregano oil.* The unique formula helps balance hydration and strengthens the skin’s natural moisture barrier to help the skin protect itself from stressors. It also visibly reduces redness and provides relief from discomfort. Pat a few drops of the non-acnegenic oil onto your face morning and night to help reveal calmer-looking skin over time.

*We consider ingredients to be naturally derived if they retain more than 50% of their molecular structure after being processed from a natural source.

What Is a Facial Oil Serum?

Oil serums are hybrid products that boast some of the benefits of both traditional serums and face oils. Typically, these serums contain lightweight plant oils and help moisturize the skin without weighing it down.

Next: 3 Reasons To Add Eye Serum To Your Routine