One of the best things about skincare is that there are products to please practically everyone, no matter your age, gender, or skin issues. But, all those choices can sometimes lead to confusion. On that list of sometimes confounding products is the face serum.

Many people still mistakenly believe that a serum and a moisturizer are interchangeable, or even that they don’t need one at all. We’re here to tell you that if you’re skimping on the serum, you aren’t doing your skin any favors. A face serum is an essential part of every skincare routine, one that can be used to supplement your regimen or boost the efficacy of your existing products.

In order to understand what a serum can do for your skin, you must first know why you need one and how serums work. Our Kiehl’s Customer Representatives are happy to share their extensive knowledge on all things face serums with you. Keep reading to learn everything you need to know about using a serum.


Essentially, a serum is a product that is applied after cleansing and toning, but before your moisturizer. They come in an array of textures that range from fluid to gel and are traditionally water-based, which makes them more lightweight and able to penetrate the skin’s surface — unlike oil-based creams and lotions, which are meant to stay on the surface of the skin and lock in moisture and reinforce the skin barrier. They usually have concentrated doses of active ingredients and are meant to address specific skin needs that can range from brightening to soothing to oil control.

While you may see some oil-based products that call themselves a serum, these are usually more like facial oils infused with active ingredients. At Kiehl’s, we refer to some of our serums as “solutions” or “concentrates” to indicate they are a concentrated treatment product.


Because they are in more lightweight formulas that use smaller molecules (rather than the emollient ingredients in many moisturizers), serums can penetrate the surface of the skin to deliver those high concentrations of active ingredients. They can also include ingredients that might not be able to be formulated as effectively into a moisturizer. For instance, the active form of Vitamin C, L-Ascorbic Acid, is highly unstable and a high percentage doesn’t do well in creams because the formulas may not support that stability. When used in a serum, like our Powerful-Strength Vitamin C Serum it allows us to add an impressive 12.5 percent L-Ascorbic Acid to the formula for maximum benefits.


Thanks to their lightweight texture and high concentration of active ingredients, there are multiple ways you can use a serum. The three most beneficial are as a treatment, a booster, and a pre-serum.

As a treatment serum

If you are dealing with multiple issues, a serum is a smart option to add a treatment component to your routine that can be used daily. For instance, if your skin is oily and you are also dealing with fine lines, apply an anti-aging serum like our Age Defender Power Serum before our Ultra Facial Oil-Free Gel Cream. This will give you the anti-aging benefits you want without the added weight that can come with the more heavy-duty anti-aging creams.

As a booster serum

If there is one specific issue you want to tackle, like dry skin, a serum can be used to “boost” the power by providing the same benefits at a different concentration. Pairing a hydrating serum like the Hydro-Plumping Re-Texturizing Serum Concentrate with a moisturizer like the Ultra Facial Cream gives you two different types of moisturizing ingredients (Glycerin and Squalane) that will add instant hydration and help lock it into the skin. If brightening or hyperpigmentation is your goal, layering the Clearly Corrective Dark Spot Solution underneath the Clearly Corrective Brightening & Smoothing Moisture Treatment helps correct the appearance of skin discoloration and rough texture for improved skin clarity and infuses skin with intense hydration.

As a pre-serum

A pre-serum is the first serum used in a skincare routine to help prep the skin to receive the benefits of any additional serums. Serums can be applied one after the other, layering in terms of texture — starting with the thinnest or most lightweight serum and working up to the thickest or heaviest serum. Our Vital Skin-Strengthening Hyaluronic Acid Super Serum can be used as a pre-serum in your routine to prep the skin to combat skin-aging stressors through delivering protective antioxidants and strengthening hydration. Our formula with 11kDa Hyaluronic Acid and an Herbal Adaptogenic Complex not only preps the skin to better receive the benefits of other serums in your routine, but it also penetrates deeply to help strengthen skin against internal and external stressors for more resilient skin and a healthy-looking complexion.

If you want to get the most optimal results for your skin issues, a serum is an integral addition to your existing routine.

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