How Does Moisturizer Work?

As the famous saying goes, “Keep skin moist, my friends”—actually, no one says that, but we really can’t stress enough how important moisturizing is for skin health. We get it: A super-basic moisturizer just isn’t very sexy. But a solid moisturizing strategy is step one for fortifying your skin barrier so that it can effectively keep the good stuff (water) in and the bad stuff (a whole host of allergens and environmental stressors) out. Without good skin-barrier function, all the fancy anti-aging ingredients you splash on your skin are wasted. Let’s put the humble moisturizer in the spotlight, shall we?

Why Use Moisturizer?

Remember, your skin is like an onion—it’s got many layers. The outermost layer is called the stratum corneum, or just SC. Most skincare products are mainly geared toward treating the topmost layer of the epidermis, the stratum corneum.

Your stratum corneum is the outermost layer of your skin. It’s your first line of defense against water loss and outside aggressors. Your moisturizers, in a nutshell, are there to help support your SC in its barrier role.

The other component to healthy skin-barrier function is natural moisturizing factors (NMFs). NMFs are found in the corneocytes of your stratum corneum and make up about 20–30% of the dry weight of your stratum corneum. These water-based molecules keep the skin elastic and play an integral part in the good-enzyme activity that is key to healthy cell turnover. Common NMFs in your skin are sodium PCA, lactic acid, free amino acids, and urea. Remember: Healthy cell turnover = healthy skin barrier = healthy skin.

Your stratum corneum has it pretty rough: The beatings of external allergens, pollutants, UV rays, weather changes, and just plain aging can really take a toll on the SC and prevent it from doing its barrier job properly. 

When these stressors impact your barrier function, water loss leads to dehydrated, irritated skin—and dry skin has long-term consequences. Neglecting to moisturize leads your poor stratum corneum into a vicious cycle: increasing water loss, letting in outside aggressors, causing inflammation, and leading to more dehydration and less absorption of moisturizers. Uncorrected, this cycle may lead to short-term nuisances like itchy, flaky skin—which turns into fine lines and wrinkles in the long term! This means that a solid moisturizing strategy that evolves with age and the season is one of the most important steps to keep your skin in tip-top shape.

As boring as skin moisturizing may sound, without this basic step, the stratum corneum’s job gets a lot harder: Layers below the SC are left not as hydrated, our bodies end up less protected from outside toxins, and further skin damage inevitably escalates the aging process. If you don’t have time for all the other serums, elixirs, or masques, just grab that jar of lotion and slather away.

How Does Moisturizer Work?

Even though scoping out a good moisturizer may seem confusing, there’s actually some method to the madness. You can divide moisturizers into three categories of ingredients based on their function: humectants, emollients, and occlusives. These three categories work together to fullfill your skin’s moisturizing needs. Understanding how these ingredients work, and finding a balance of the categories, is the key to cracking your skin’s moisturizing code.

The reality is that your skin will constantly change. So, instead of hitting the reset button and tossing out your current moisturizer—the one that took you forever to find—figure out which of these categories you might need just a little more of, and you’ll master your moisturizing needs through the seasons. Hopefully, thinking about it in this manner will help you confidently troubleshoot and adjust your moisturizing routine when your skin decides to be dramatic.

Category 1: Humectants (The Water Stuff)

Humectants are water-grabbing ingredients that help your skin maintain a healthy moisture level, which is key to maintaining that desirable, supple feel. Your skin naturally has its own water-holding system in the form of natural moisturizing factors (NMFs), and the humectants in skincare are there to support them. 

Some gold-star humectants used in moisturizers are glycerin, hyaluronic acid, and glycols. Humectants are so important that many skincare products are humectant-centric, such as essences, ampoules, hydrating serums, and mists. Who needs humectants? From the oiliest to the dryest skin, every type can enjoy the benefits of humectants. They are especially crucial if you want your dry skin to achieve that supple look!

Category 2: Emollients (All Things Oil)

Emollients fill in the rough patches of your skin and instantly give it that soft, smooth feel. These ingredients are usually lighter, oil-based substances such as jojoba oil, caprylic/capric triglyceride, squalane, and coconut alkanes. The most common emollient-centric products are, of course, face oils! 

These products have become very popular in the past decade. As a result, many brands have released their own “miraculous, antioxidant-rich, wrinkle-correcting, time-stopping, sustainably harvested” face oil. These are great little moisturizer boosters, but don’t take the fancy “turn back time” claims too seriously.

Who needs emollients? If you moisturize, there’s a solid chance that you already have some emollients in your life. These can be great for both dry and oily skin types; it’s just about finding the right oil. Just adding a few drops as a last step to your routine can help elevate your go-to moisturizer on days when it’s just not cutting it.

Category 3: Occlusives (Seal That Moisture In!)

Your skin is your barrier against outside aggressors like UV light and pollutants, but sometimes your skin barrier needs a little help. Occlusives are there to help your skin do that job even better. Occlusives are heavy, fatty, waxy substances that form a physical, water-resistant barrier over your skin to seal in moisture. Some common occlusive ingredients are petrolatum, butters, waxes, and heavier silicones. Occlusive-forward products such as balms or salves are great for spot-treating ultradry patches of skin.

Who needs occlusives? You guessed it! As with the other two categories, everyone could benefit from having some occlusives in their lives. But if you’re dry, seriously consider occlusives. Slather on that butter, balm, or petrolatum. Trust us—your skin will thank you.

Ingredients of Moisturizer

If you stalk online skincare-ingredient databases (like we do—we’re so cool), you’ll see that everything claims to be some sort of moisturizing miracle. But which ingredients are the fairest of them all? Here’s a quick introduction to some of our chemists’ favorite moist-making ingredients!

1. Humectants

Nowadays, it seems everything is “hydrating.” The reality is, there’s nothing out there that ranks all humectants. Humecants can vary a lot in terms of molecular weight and secondary benefits. One strategy is to have a blend of these humectants below to make your hydration game more well rounded.

UREA (Molecular weight: 60)

Also part of the NMF category. Unlike other humectants, urea seems to improve barrier function in the long run on top of instant hydration benefits. In fact, as skin ages, urea becomes more helpful in body care. Yes, there are people out there that claim “Urea comes from pee! I will not put pee on my face!” Rest assured that the urea in your cream does not come from urine extract.

LACTIC ACID (Molecular weight: 90)

Also part of the NMF category. Lactic acid is a very versatile ingredient: In addition to being a great hydrator, it can also be used in chemical exfoliation.

GLYCERIN (Molecular weight: 92)

You’ll find this in many, many, many products. The reason is—it works! This small molecule can wedge itself into the fatty stratum corneum’s lipid matrix, giving skin that nice, supple, flexible texture.

PANTHENOL (Molecular weight: 205)

Also known as pro-vitamin B5, panthenol is considered both a humectant and an emollient. It also has great soothing properties.

COLLAGEN (Molecular weight: 300,000)

Many people may associate collagen with anti-aging claims. The reality is, though, that topical collagen can not replace your natural collagen. However, this chubby molecule can be a great hydrator!

HYALURONIC ACID (Molecular weight: anywhere from 20,000 to 2 million+)

Probably one of the most prolific categories of hydrators! You’ll hear claims, from hydration to plumping to even anti-aging. Most HAs on the market are high-molecular-weight polymers—in the 2 million-plus size range. This means molecules sit on the skin’s surface, effectively keeping it hydrated all day.

There are other forms of HA that are much smaller. Some studies suggest that smaller HAs can penetrate the skin to plump, hydrate, and even bring anti-aging benefits. However, some people can be sensitized by these small HAs.

2. Emollients and Face Oils

Over the years, face oils have gained a lot of popularity, and every brand is brewing its own version. You’ll find that they all seem to be 100% pure, 100% organic, 100% potent, and 100% exaggerated. Regardless of the claims, face oils are a great addition to your routine to boost nourishment, add glow to dull skin, smooth skin surface, and improve overall skin pliancy. While oils are lousy stand-alone moisturizers, there are a few key scenarios where a face oil can really elevate your skin routine.


Consider a face oil for the following scenarios:

“I love my moisturizer, but my skin still gets a little dry.” Skin constantly changes. Just from stress, age, lifestyle, and hormones, your moisturizing requirements can really fluctuate. If you’re loyal to your moisturizer and know your skin needs just a little help in the moisturizing department, consider adding a couple of drops of face oil to give it that oomph.

“I’m dry, but not petrolatum/balm (cactus) dry.” We get it—petrolatum and other heavy-duty occlusives feel kind of gross. Not to mention the disco-ball- shiny look is so not in right now. Consider face oils, their lighter (albeit less effective) cousins.

“My skin is a little dull.” A quick way to add back that healthy glow to skin is with a couple of drops of face oil.

“I have acne, but my acne topicals are drying me out, and my current moisturizer isn’t cutting it.” Look for a lightweight emollient such as linoleic, acid–forward plant oils or squalane.

Before you try to figure out if you need rose hip, watermelon seed, argan, or whichever plant oil, consider squalane, which is a purely saturated hydrocarbon. In layperson’s terms, this means that it’s super vanilla and is highly unlikely to irritate you or cause you to break out. It’s a great starting point for beginners of all skin types.

3. Occlusives

Occlusives are your butters, waxes, and petrolatum. As the name suggests, they help shield your skin from the elements. When your skin-barrier function is compromised, occlusives help protect skin and seal in moisture. The catch is that occlusives can feel heavier and greasier than the other categories. People with oily skin need lighter gel creams that contain little to no occlusives, while those with dry skin may want to opt for a heavier cream that has more. We do always recommend having an occlusive balm (think Vaseline, Aquaphor, and the like) to spot-treat those troubled areas!

PETROLATUM (good ol’ Vaseline)

Still the gold-standard occlusive. In recent years, it’s seen some terrible press in chemophobic groups along the lines of “It causes breakouts and also cancer.” The reality is, cosmetic-grade petrolatum is highly refined—which means it’s exceptionally “clean” (free of potentially irritating and harmful residue). It doesn’t clog pores, but it can cause breakouts by sealing in dirt and grime if you are lazy about cleansing.


The lighter version of petrolatum is much less occlusive, but feels better in a cream formula. Fun fact! You’ll be surprised how much these ingredients affect the feel of the final product. Just a 1% difference in mineral oil or petroleum jelly content completely changes the feel of the cream.


Shea in butter form is a great, versatile natural occlusive. With the clean movement, you may stumble upon “raw shea butter.” People think ultranatural means ultrasafe and free from scary chemicals. The reality is that plants are complex. In its raw form, shea butter can be irritating. We recommend sticking to refined shea; you’ll have a range of options for texture.


This is a great occlusive derived from wool. It can be an allergen, though, so look for medical-grade lanolin and definitely make sure you patch-test before using!


More great occlusives that often come from natural sources such as beeswax, candelilla, carnauba, and others. Their main drawback is that they’re, well, waxy. And wax’s high melting point makes it unsuitable for high-level use.


This is a vast category, but regardless of the material type, the general unifying theme of silicones is simply, “These feel awesome!” Silicones can be effective occlusives without much of the heaviness. If you have oily skin, silicone gel creams can be a great way for you to boost your hydration game between seasons—or when your skin goes through changes—without that dreaded greasy feel. How do you spot a silicone gel cream? Look for terms such as dimethicone or “dimethicone crosspolymer” fairly high on the ingredient list.

Staple Products vs. Booster Products

Staples are your more traditional moisturizers, which are a combination of humectants, emollients, and occlusives in one milky, creamy formula. Booster products are usually made up of only one type of moisturizing ingredient. They are great to have in your arsenal so you can adjust to your skin’s needs when you find your staple product is just not quite cutting it.

Moisturizing Routine For Different Types of Skin

Based on the charts of all the crazy product types, moisturizers are a massive category. Not to mention that many of these product types have overlapping functions. So, when you’re developing a good moisturizing routine, try following these simple guidelines according to your skin type.

Oily Skin

For those of you with oily skin, lucky you! That usually means your skin is already better at sealing moisture in. Your moisturizing routine can be a lot simpler than it is for those with dry skin. The key is to focus on a humectant-centric routine with a dash of lightweight, oily-skin-friendly oils. 

Another great one-and-done product choice is silicone creams. Look for products with dimethicone or dimethicone crosspolymer high on the ingredient list for weightless moisture.

Dry Skin

Layering is your friend! We recommend having an arsenal of products to take you through various skin changes.

  1. Humectants: Start with a loaded hydrating serum. Though ingredients such as hyaluronic acid are super popular, we recommend serums that feature a blend of humectants over a serum that only uses one star ingredient.
  2. Moisturizer: Look for lotions or creams that have an occlusive such as mineral oil, petrolatum, or shea butter relatively high up the list (think third to fifth position).
  3. Balm/petroleum jelly: Keep one handy for those pesky little dry spots that may pop up here or there.

Sensitive Skin

Rule 1: Keep it as simple as possible and start with one single moisturizer. More steps = more chances of irritation.

Rule 2: Seek out helpful skin barrier–supporting ingredients. Lipid-mimicking ingredients like ceramides, cholesterol, and fatty acids can really help elevate your moisturizer game and get your skin back on track. Ceramides in particular can help strengthen your skin barrier, help it retain moisture, and even protect from outside environmental aggressors. Studies have even shown that ceramides are helpful to those who struggle with eczema and psoriasis. (Ask your dermatologists how to incorporate this ingredient into your treatment plan.) It’s also a great idea to include soothing ingredients into your moisturizing routine. Check out page 165 for some of our favorite soothers!


Here’s the absolute minimum you need to know:

#1. Pick at most two products in the toner, essence, water, serum, and ampoule category: As you can see from our product diagram, these products are mostly humectant only and have overlapping benefits. It gets confusing fast. The more cumbersome your routine becomes, the less likely you are to be consistent. When it comes to skincare, consistency is key. We suggest picking just one or two products from this category to suit your needs.

#2. Don’t get greedy: We all want that one product that solves all our problems. But sometimes that means you get a Franken-product that doesn’t let you benefit from any of the good ingredients. So, as tempted as you may be to buy a serum that brightens, anti-ages, hydrates, and battles pigmentation changes, find a simple yet effective hydration serum first. Remember: hydrated, healthy skin first, and then move on to the other good stuff.

#3. Remember layer order: If you end up lost and confused in your layers, just remember: humectant, emollient, occlusive.

Seasonal Change To Consider For Your Moisturizer Needs

Environment can be a big factor in your moisturizer needs. You may find that moving, or vacationing to a new, unusual location, suddenly throws your moisturizing needs out of whack. Some things to consider include how hot (or cold) and how moist the air is going to be, both indoors and out. After all, your dry, chapped winter skin isn’t going to get much happier when you head inside to an overheated ski cabin!

Headed to the frigid Arctic? Be sure to have an added oil or balm on hand to help with dry, chapped skin.

Vacationing in the tropics? Consider a more weightless hydrating gel or lighter moisturizer that’s able to keep up with your skin’s moisturizing needs without feeling too heavy in the humid heat.

That meditation retreat in the desert? Either add a hydrating gel underneath your current moisturizer, or bring a lightweight oil to add over, to minimize that tight, dry, parched feel.

FAQs About Moisturizers

Q: I heard using hyaluronic acid in dry climates ends up making your skin drier.

A: If you are solely relying on hyaluronic acid, it can certainly be a problem. Use some occlusives to seal in moisture in a dry climate!

Q: If I use too much chapstick, will my lips forget to hydrate?

A: Sadly, your lips are already a little handicapped when it comes to staying hydrated, since the lips don’t have any sebaceous glands. There’s nothing wrong with using chapstick often, but if you’re experiencing long-term dry lips where you’re having to apply multiple times a day, there may be a bigger issue here. Make sure you’re using proper lip balms that are heavy in petrolatum and butters and have fewer cooling ingredients such as menthols and peppermint oil.

Q: I have oily and/or acne-prone skin—will moisturizers with oils make me break out?

A: This is highly product-dependent! In fact, the “oil-free” claim is probably one of the most pointless claims in skincare. The reality is, finding your pore-clogging triggers could take a bit of detective work. Always patch-test a product to figure out your skin’s quirks!

Q: Does everyone need moisturizers? Even if I’ve never used one my whole life?

A: If your skin has been doing perfectly fine without a moisturizer, then please donate your DNA to science so we can figure the secret genetic code behind perfect skin. In all seriousness, though: No, you don’t need a moisturizer if your skin does fine without one. However, if you’re noticing unwelcome changes and want to start picking up some products, moisturizer is an important foundation of virtually every rounded-out routine.

Leave a Comment