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Serum vs. Moisturizer: Why You Need Both

From oils and moisturizers to serums and masks to cleansers and toners, today’s plethora of skincare options can feel overwhelming. So when skincare experts recommend using both serum and moisturizer, it’s only natural to wonder why.  Should you use serum before or after moisturizer? And what’s the difference between serum vs. moisturizer anyway?

We’re diving deep into this essential skincare knowledge with this complete guide to serums and moisturizers.

What Is A Serum?

Simply put, a serum is a light, easily absorbed skincare product designed to penetrate, improve, and nourish the skin by using smaller molecules and concentrated active ingredients. A key difference between serum and moisturizer is that serums are not necessarily meant to moisturize, but rather to target and treat specific skincare concerns.While all of our serums contain squalane to provide added hydration and help drive active ingredients deeper into the skin, serums are generally too light to provide adequate, all-day moisturization all on their own. Their key benefit is the delivery of an intense dose of active ingredients aimed at achieving your skincare goals.This powerful dose of actives is one of the reasons why we say it’s not necessary to layer Biossance serums. In fact, some ingredients can react with each other or with sunlight to cause sensitivity. Instead, we recommend choosing products based on your skincare concerns. If you’d like to address more than one, you can use one serum during the day, and a different one at night. And don’t worry - we call out nighttime-only ingredients right on the bottle.Squalane + Copper Peptide Rapid Plumping Serum with dropper open

Which Serum Should I Choose?

If you’re looking to plump fine lines and wrinkles….

Choose our Squalane + Copper Peptide Rapid Plumping Serum. Our powerful blend of copper peptides, hyaluronic acid, and sugarcane-based squalane work together to target signs of aging, instantly hydrating and plumping wrinkles with continued improvement over time.

Shop Squalane + Copper Peptide Rapid Plumping SerumIf you’re looking to improve the look of hyperpigmentation….

Choose our Squalane + Vitamin C Dark Spot Serum. If you have sensitive skin and have struggled with Vitamin C products, we recommend trying this one. Our shelf-stable 10% Vitamin C serum is carefully calibrated to minimize irritation while our hero ingredient squalane gently drives this potent antioxidant deep into the skin and prevent over-drying.

Shop Squalane + Vitamin C Dark Spot SerumIf you’re looking to smooth uneven texture…

Choose our Squalane + Lactic Acid Resurfacing Night Serum. Suitable for every skin type, this serum uses 10% lactic acid to powerfully - but gently - dissolve dead surface cells to reveal brighter, more even skin underneath. Clinical trial participants reported increased hydration in just one use, and improvement in the look of enlarged pores after a single use. A quick note: as the title suggests, our lactic acid serum is a nighttime-only product. In addition, sunscreen is imperative when using this powerful exfoliating treatment. Be sure to wear it every day, if you aren’t already.

Squalane + Lactic Acid Resurfacing Night SerumSqualane + Probiotic Gel Moisturizer

What Is A Moisturizer?

Moisturizers have two simple functions: hydrate the uppermost layers of the skin while shielding against environmental stressors. When comparing the texture of  a serum v. moisturizer, the latter is thicker. That richer texture helps to lock in moisture to help prevent skin from drying out. Some, such as our Squalane + Omega Repair Cream, can also strengthen the skin’s moisture barrier, the protective layer of moisture and skin cells that keeps moisture in and bacteria out.

The bottom line: moisturizers hydrate the uppermost levels of the skin while shielding against environmental stressors.

Do I Need Both?

The biggest difference between serum and moisturizer is not what’s included, it’s what serums don’t include. Serums don’t contain occlusive ingredients meant to seal in moisture. They also use fewer lubricating and thickening agents. 

And while some moisturizers may contain active ingredients, these are meant to improve the skin’s surface. If you’re looking to improve the look of your skin at a deeper level (by treating hyperpigmentation, for example) you’ll want to reach for a serum.So when comparing  serum vs. moisturizer, the main thing to remember is that serums treat, and moisturizers hydrates and protects. And that’s why you need both.Squalane + Vitamin C Dark Spot Serum

Serum Vs Moisturizer: A Side-By-Side Comparison


Lightweight, fluid textureHigh concentration of active ingredientsDon’t seal in moistureMeant to treat specific skin concerns


Richer, thicker textureMay not address additional skincare concernsHydrate and protectAimed at locking in moisture

When Should You Use A Serum In Your Skincare Routine?

Serums should be applied after cleansing and before moisturizing. Applying your serum first enables its active ingredients to penetrate deeply in to the skin, while your moisturizer then hydrates and locks in those benefits while shielding the skin against stressors such as dry air and environmental pollutants.Here are a few of our favorite targeted pairings:For hydration:

Combine Squalane + Copper Peptide Rapid Plumping Serum to hydrate and plump with Squalane + Omega Repair Cream to lock in moisture and improve skin barrier function.

To address signs of aging:

Use Squalane + Vitamin C Dark Spot Serum to attack hyperpigmentation and fine lines and Squalane + Omega Repair Cream to improve hydration and elasticity.

For oily skin:

Resurface and reduce the look of pores with Squalane + Lactic AcidResurfacing Night Serum while hydrating and reducing redness with our lightweight Squalane + Probiotic Gel Moisturizer

To soothe sensitivity: 

Get a burst of calming hydration with Squalane + Copper Peptide Rapid Plumping Serum, then seal and soothe with our Squalane + Probiotic Gel Moisturizer

Shop SerumsShop Moisturizers
Christine Tusher
Christine Tusher Writer and expert
As a lifestyle writer and journalist, I love sharing my passion for ocean conservation and obsession with clean beauty. I’ve tried almost every trend and ingredient, and Biossance’s science-backed formulas are the only ones that consistently calm my reactive skin and make it smoother, clearer, and healthier. I’m so excited to be on this journey of skincare innovation with Biossance, and to share it with you!

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