The Anatomy of a Moisturizer

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This article first appeared in the Winter 2022 issue of New Beauty. Click here to subscribe

In a well-balanced skin-care regimen—cleanse, treat, moisturize, protect—moisturizer is essential for a healthy complexion. But, do you really know what’s in the cream that’s responsible for all that youthful quenching and plumping, and which formulation is best for your skin type? We investigate.

Formula Facts

There are three main categories of ingredients that make up a moisturizer: humectant, emollient and occlusive. “Some of these ingredients actually overlap and work in more than one way to keep skin hydrated,” says San Francisco dermatologist Amelia Hausauer, MD. A good rule of thumb to remember: After cleansing, always apply skincare products thinnest to thickest, with the exception of SPF, which should be last. Here’s the breakdown.

01 / Humectants

According to cosmetic chemist Krupa Koestline, humectants are hydrophilic (water-loving) ingredients that work by attracting moisture to the stratum corneum, or the outermost layer of the epidermis. Think of them like a magnet: they draw water into the skin and hold it there for temporary hydrating and plumping that may make lines and wrinkles look smoother. “They’re known for their ability to retain moisture, but not all humectants work via the same mechanism,” says Dr. Hausauer. “Some supply moisture, like glycerin, sorbitol, aloe vera, honey, and hyaluronic acid, which holds 1,000 times its weight in water and is partially responsible for hydrating the deeper part of the skin called the dermis. It’s also why hyaluronic acid fillers can swell in the face after injections.” Others, such as lactic acid and urea, help shed dead skin cells first, then even out moisture levels.

Many skin-care pros agree that a good moisturizer should contain all three of these ingredient types to deliver optimal results.

It’s important to note that humectants can also work against you in the wrong environment. “When the air is drier and less humid, like in desert climates, humectants can pull too much water from the lower layers in the skin,” says celebrity aesthetician Nerida Joy. “This can actually age the skin faster. In these climates, I recommend using more occlusive products, especially for those with combination/dry skin.” (More on occlusives later.)

02 / Emollients

“Emollients can function as humectants or occlusives—they are not an exclusive category,” explains Koestline, noting that their main function is to improve skin’s smoothness and appearance. “They are generally grouped by how they spread on the skin and can be combined with different humectants and occlusives to produce a certain feel on the skin.” Omaha, NE dermatologist Joel Schlessinger, MD describes them as moisturizing agents that soften and smooth by filling in the cracks between dead skin cells (signs of a damaged skin barrier). For this reason, they’re particularly good for irritated, sensitive, inflamed, or reactive skin, though all skin types can use them.

“Some popular emollients are squalane, dimethicone, ceramides, lipids, fatty acids, butters, and colloidal oatmeal,” Dr. Schlessinger says. Oils are also emollients, and Joy says some are comedogenic and may clog pores, like coconut oil— be aware if you’re breakout-prone— whereas others are noncomedogenic, like squalane. Another ingredient commonly used in moisturizers is panthenol (or provitamin B5), which Dr. Hausauer notes is unique because it functions as both a humectant and emollient in one.

03 / Occlusives

The opposite of humectants, occlusives are hydrophobic (oil-loving) and don’t hydrate on their own, but rather create a physical barrier on the surface of the skin to help reduce water loss (think balms and ointments). “These are the heaviest and stickiest end of the spectrum,” Dr. Hausauer says. “Because they form a seal, these should always be the last step in a skin-care regimen.” The K-beauty “slugging” trend brought this category into the limelight and is based on the idea of coating your face with a thin layer of an occlusive moisturizer like petrolatum (Vaseline)— hence skin looks like a slimy slug—to lock in moisture when skin is very dry. “In general, occlusives are best for severely dry or eczema-prone skin, or those healing from ablative procedures like a laser or chemical peel,” adds Dr. Schlessinger.

Other examples of the ingredient include, lanolin, beeswax, olive oil, mineral oil, and dimethicone and other silicones. “Although silicones can be considered occlusive, they evaporate quickly without penetrating the lining of a pore,” Joy explains. “Their molecular fiber structure is loose, which enables skin to still ‘breathe’ without clogged pores, and therefore they can be used in formulas for combination and oily skin types.”

Last year, “ultra” moisturizers were trending big, like Olay’s Ultra-Rich Regenerist and Farmacy’s Honey Halo that have a super thick consistency almost like butter and melt into dry skin. “These get their texture from the high concentration of occlusives like vegetable oil, shea butter and paraffin, which allow them to glide onto skin, feel richer and provide long-term moisturization,” says Koestline.

What about moisturizers with SPF?

“I don’t mind them, but I always recommend applying a separate sunscreen on top because we rarely use enough moisturizer to provide adequate protection—two finger lengths or a nickel-size for the face,” says Dr. Hausauer. “And oftentimes, the SPF in combination products is lower than 30.”

Ideal Combination

Many skin-care professionals agree that a good moisturizer should contain all three of these ingredient types in balanced amounts to create a synergistic effect and deliver optimal results. “Though there are exceptions to the rule, as some gel or oil-free moisturizers might do without an occlusive agent in order to create a more appealing texture for an oily or acne-prone skin type,” Koestline explains. “It’s important to remember that our skin’s outer layer is made up of a phospholipid bilayer, so just using occlusives or humectants will not cut it. It’s best to use a balanced approach to moisturize skin effectively.”

As Dr. Hausauer notes, it usually comes down to skin type. “Those with dry and sensitive skin want something that will soften the outer layer and restore its structure—an emollient—while also having something that will lock in that moisture, like an occlusive. In contrast, oily or acne-prone skin may prefer lessocclusive ingredients, not because they inherently cause breakouts—petrolatum is actually noncomedogenic—but because they do not let the skin breathe and trap natural oils underneath, making skin more likely to breakout.”

Where you live plays a role as well, says Joy. “Someone in a humid environment like Florida may find a humectant-only product to be perfect, whereas someone with drier, more mature skin living in the desert would typically benefit from both an occlusive moisturizer and an emollient product to keep their skin youthful and healthy.”

Hydration Station

1 / 6

For Sensitive Skin

Oil-free La Roche-Posay Toleriane Double Repair Face Moisturizer ($20) tops many derm’s lists because it uses ceramides to prevent moisture loss and glycerin to attract water to the skin’s surface.

2 / 6

For Post-Procedure Skin

Made for compromised skin, such as after an in-office treatment like microneedling, Alastin Ultra Light Moisturizer ($72) includes ceramides, panthenol and anti-inflammatories, and feels richly hydrating without a heavy texture.

3 / 6

For Acne-Prone Skin

We love the light, refreshing feeling of DERMALA OAT So Sweet Daily Moisturizer ($40), which instantly calms stressed skin while banishing acne-causing bacteria.

4 / 6

For Dry Skin

The mix of four types of hyaluronic acid, glycerin, squalane, oils, and shea butter make HydroPeptide Power Luxe Hydra-Rich Infusion Cream ($148) a luxurious nighttime treat for parched skin.

5 / 6

For Oily/Combo Skin

Powered by 16 vitamin-rich greens and superfoods, including hyaluronic acid and oil-busting tulsi extract, Odacite Green Smoothie Quenching Crème ($68) locks in weightless moisture with zero greasiness.

6 / 6

For Aging Skin

Founder Hillary Peterson calls her new True Botanicals Chebula Extreme Cream ($110) “an anti-aging triple threat,” as it delivers extreme moisture and skin barrier optimization with humectants, emollients and occlusives.

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