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What Is Moisturizer? How It Hydrates Your Skin and How to Choose the Best Formula (If You Need One)

Find out if your face cream measures up.
What is moisturizer

You probably apply it every day, twice a day. It keeps your skin from feeling dry, and it instantly gives you a smoother and healthier-looking complexion.

I'm talking about moisturizer, of course, and if you're like most people, it's an essential part of your skincare routine. But have you ever wondered how it actually works—and what it's really doing to your skin?

In this tutorial, you will learn how moisturizer affects your skin, who needs it (and who doesn't!), which ingredients to look for, and which products I recommend most.

What Is Moisturizer?

Believe it or not, the term "moisturizer" was originally a marketing invention. It was based on the idea that moisturizer works by simply moistening the skin, when in fact, it does so much more.

At its most basic, moisturizer is a topical treatment that reduces the symptoms of dry skin and makes rough skin feel smoother. 

Rather than just wetting your skin—which can weaken its natural protective layer—an important role of moisturizer is to trap water and prevent it from escaping.

Depending on what else is in the formula, moisturizer also repairs the skin barrier, delivers anti-aging and/or anti-inflammatory ingredients, and alleviates discomfort from certain skin conditions such as dermatitis and eczema.

In terms of texture, most moisturizers are emulsions of oil and water, giving them the consistency of a cream or lotion. However, formulas with a higher concentration of water will feel more like gels (and are often oil-free), while formulas with lots of oil will tend tend to be thicker, richer balms. 

What Does Moisturizer Do to Your Skin?

A well-formulated moisturizer performs three main functions for your skin:

1. Replenishes Water Content

When moisture is lacking, the outermost layer of your skin becomes dry, inflexible and prone to cracking. Certain ingredients called humectants can address this by pulling in and holding onto water. "Humectants are mostly low molecular weight substances that bind water into the stratum corneum," says Dr. Hadley King. "They need to be used along with the other components in order to retain the water content."

2. Prevents Water Loss

To prevent the evaporation of water from your skin into the atmosphere, moisturizers combine humectants with occlusives. These are ingredients that form a protective barrier on your skin to stop moisture loss. Just be aware that occlusives don't deliver any hydration themselves. "They put a sealant on your skin by coating the top layer," says Dr. Elizabeth Tanzi. "This is different from pulling in water and hydrating skin."

3. Repairs the Skin Barrier

Barrier-repairing ingredients treat the underlying cause of dryness—a damaged skin barrier—by replicating the natural balance of lipids found in healthy skin. "The healthiest skin is made up of the correct balance of three key lipids: cholesterol, ceramides and free fatty acids," explains Dr. Mervyn Patterson. "They are skin's natural protection and ideally, they exist in a ratio of 1:1:1." These substances repair the skin barrier by sealing up the cracks between skin cells. "If ceramides are applied with other lipids such as cholesterol in a combination similar to that found in the skin barrier, this further enhances barrier repair," adds Dr. Justine Hextall.

Does Everyone Need Moisturizer?

Contrary to popular belief, not all skin requires moisturizer. According to Dr. Rachael Eckel, moisturizer is only needed by the 15% of the population with genetically dry skin that doesn't function properly. "They tend not to have visible pores and have dry body skin, with conditions like eczema."

For the rest of us with "normal" skin, a daily moisturizer may do more harm than good.

"When a moisturizer is applied to the skin surface, cells on the surface detect a large amount of moisture and send a message to the body to stop delivering water to the skin," says Dr. Zein Obagi in his book, The Art of Skin Health Restoration and Rejuvenation. "Moisturizers are also detrimental in that they interfere with the natural exfoliation and desquamation of corneocytes [dead cells]... [which] accumulate on the surface instead."

In other words, moisturizer can make normal skin "lazy," so it's less able to hydrate and renew itself—which could lead to increased dryness, dullness, clogged pores and signs of aging over time.

Even more worrisome is the possibility that moisturizer might harm rather than heal the skin barrier. "Moisturizers alter the balance of water, lipids and proteins in the skin, which leads to a compromised barrier function and to an acquired skin sensitivity," says Dr. Obagi. His thoughts are backed up by studies like this one, which found that "long-term treatment with moisturizers on normal skin may increase skin susceptibility to irritants."

My suggestion? If you're not sure if your skin needs moisturizer, try going without it for about a month. "Scientifically, the very top layer of your skin turns over every two weeks, so I'd say it would take about two to four weeks for you to have new skin that won't require moisturizing," says Dr. Sandy Skotnicki. During this time, you can use a hydrating serum instead, along with sunscreen.

Otherwise, if you do feel you need moisturizer, make sure you're using one with the right combination of ingredients to keep your skin barrier intact and healthy. Here's what to look for....

What to Look for in a Moisturizer

For best results, scan labels for the following ingredients:

✓ Humectants

These lightweight hydrators attract water from both the air and the deeper layers of your skin. Examples of humectants are glycerin, hyaluronic acid, sodium hyaluronate, aloe, panthenol, honey, gluconolactone, propylene glycol, urea and alpha-hydroxy acids.

✓ Occlusives

To lock in the water from your humectants, occlusives form a protective barrier that prevents moisture loss. Examples of occlusives include jojoba oil, coconut oil, shea butter, fatty alcohols, lanolin, beeswax and lethicin.

✓ Barrier-Repairing Ingredients

Ceramides, cholesterol and fatty acids are the three key lipids that repair your skin barrier. (Look for fatty acids listed individually—especially stearic acid and palmitic acid—or oils that contain them, like shea butter and coconut oil.) Most moisturizers contain fatty acids, but if you have particularly dry or sensitive skin, you'll get the best results from products with all three barrier-repairing ingredients.

✓ A Preservative System

Without preservatives, moisturizers become a breeding ground for bacteria and mold. If you're looking to avoid parabens, your choices include food-grade preservatives (such as sodium benzoate and potassium sorbate); alcohols (such as ethanol, benzyl alcohol and witch hazel); essential oils (such as rosemary, neem and tea tree oil); plant-based preservatives (such as gluconolactone); and synthetics (such as dehydroacetic acid and phenoxyethanol).

✓ Insoluble Sunscreen Filters (Optional)

Daily sunscreen is essential, but if you'd rather not apply two different products, a hydrating SPF can double as a daytime moisturizer. For the safest and most effective protection, look for products with zinc oxide, Tinosorb M (bemotrizinol), Tinosorb S (bisoctrizole) or Tinosorb A2B (tris-biphenyl triazine). These insoluble filters not only offer superior UVA and UVB protection, but also have large particle sizes that don't get absorbed into the body or disrupt your hormones.

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From The Skincare Edit Archives

What to Avoid in a Moisturizer

Here are the moisturizer ingredients that I suggest limiting or avoiding:

✗ Fragrance

Although it is the number one cause of skin irritations and allergic reactions to personal care products, fragrance is present in most moisturizers. (This study found it in 83% of drugstore creams!) It's not just synthetic fragrance that is a problem; so are essential oils and their components (like geraniol, linalool and limonene). If you can't avoid them altogether, at least make sure they're near the end of an ingredients list, in a low concentration. Also be aware that "fragrance-free" doesn't guarantee there's no fragrance—it just means the product doesn't have a noticeable odour. Masking agents may be present, and they can be just as problematic as fragrance chemicals.

✗ Silicones

Companies love to use silicones because they're cheap, they make moisturizers feel velvety, and they instantly smooth out the skin's surface. But they don't actually hydrate—their only function is to form a film on top of your skin. The problem is, this film has a tendency to trap acne-causing debris. "A lot of moisturizers contain silicone to fill in flaws and create a smooth finish, but they also fill in pores," says facialist Kate Kerr. Furthermore, silicones can slow down your skin's natural exfoliation process, leading to dull, dry skin with continued use. I suggest looking for moisturizers that are either silicone-free, or that don't contain silicones in the first five ingredients (which usually represent about 80% of the product).

✗ Mineral Oil

Just like silicones, mineral oil creates a smooth texture and works by forming a seal on top of the skin—but it can also be too occlusive. "Mineral oils can retain moisture so effectively that the skin will become too moist," says Dr. Jetske Ultee. "Your skin will look good at first (because the lines are stretched out), but in the long run various cellular processes will work somewhat less efficiently. Eventually this will lead to your skin not being able to protect itself and you find yourself in a vicious circle; your skin quickly dries out if you don't put any cream on and so you keep applying it." Dr. Ava Shamban agrees: "Creams that combine mineral oil and paraffin can actually damage the skin barrier and increase water loss."

✗ Polyunsaturated Fatty Acids

Moisturizers with a high concentration of polyunsaturated fatty acids (PUFAs) can cause oxidative damage that will age your skin. PUFAs "have limited stability," explains Dr. Sharyn Laughlin. "This can affect the shelf life of skincare products containing them." Once a PUFA-laden moisturizer oxidizes (goes rancid), it releases free radicals, which are dangerous molecules that attack cell DNA. "A rancid oil on the skin, no matter how anti-aging it was when stable, will have the opposite effect on your skin," says facialist Abigail James. That's why I recommend avoiding any moisturizer with PUFA oils in the first five ingredients. (If you don't know whether an oil is polyunsaturated, Google "[oil name] fatty acid profile" and you should be able to find out.)

✗ Oleic Acid

Another fatty acid to consider limiting is oleic acid, but not because of oxidation. (As a type of monounsaturated fatty acid, it is actually quite stable.) The problem is that oleic acid "can create tiny holes in your skin and therefore damage your skin's natural barrier," says Dr. Leslie Baumann. Olive oil is high in oleic acid and therefore one of the worst offenders. This study found that it significantly weakened the skin barrier and induced redness even in people with no history of dermatitis. Other high-oleic oils include camellia and almond oils.

✗ Soluble Sunscreen Filters

If your moisturizer has sunscreen, make sure it doesn't contain any soluble filters. These include avobenzone, oxybenzone, homosalate, octisalate, octocrylene, octinoxate, meradimate, cinoxate, padimate O, ensulizole, dioxybenzone and sulisobenzone. "I believe that every human should absolutely avoid these petrochemical UV filters," says Dr. Denis Dudley, endocrinologist and co-founder of The Sunscreen Company. "Soluble filters are all absorbed through human skin... causing hormone disruption, DNA mutations and epigenetic changes. There is [also] little evidence that sunscreens using soluble petrochemical UV filters can prevent skin cancer."

✗ Emulsifiers

When you think of detergents in skincare, you probably think of cleansers, and specifically, sulfates—which strip away the skin's protective oils and cause dryness and irritation. But guess what? Emulsifiers, a common ingredient in moisturizers, belong to the same ingredient family, and can have a similar effect on your skin. "Emulsifiers are used in skincare to bind oil and water together to form an emulsion," explains facialist Andy Millward. "When water is then applied to the skin, as in the case of the next time you wash your face... the lipids from your skin barrier, along with the emulsifiers can be washed away." There are so many different emulsifiers (such as glyceryl stearate, cetearyl olivate and polysorbate-80) that it can be a real challenge to avoid them entirely, but you may find they're okay in lower quantities.

The Best Moisturizers for Your Skin

As you can imagine, the "perfect" moisturizer probably doesn't exist, based on the challenges of formulating this type of product. But here are some of the best creams I've found to date, which tick off as many of the boxes as possible:

Best Splurge: Augustinus Bader The Cream

Augustinus Bader The Cream

Augustinus Bader The Cream

Augustinus Bader The Cream is packed with fatty acids, ceramides and the brand's anti-aging complex of vitamins, amino acids and antioxidants. Even still, it has an ultra-light texture (which is why so many celebs swear by it!).

Best Budget: The Ordinary Natural Moisturizing Factors + HA

The Ordinary Natural Moisturizing Factors HA

The Ordinary Natural Moisturizing Factors + HA

The Ordinary Natural Moisturizing Factors + HA (reviewed here) gives you fatty acids, ceramide precursors, hyaluronic acid and amino acids—all in a super affordable, lightweight cream.

Best for Sensitive Skin: EltaMD Barrier Renewal Complex

EltaMD Barrier Renewal Complex

EltaMD Barrier Renewal Complex

EltaMD Barrier Renewal Complex is a derm favourite for dry, sensitive and compromised skin. It boasts all three types of barrier-repairing ingredients (ceramides, cholesterol and fatty acids) plus niacinamide and hyaluronic acid.

Best for Dry Skin: Drunk Elephant Lala Retro Whipped Cream

Drunk Elephant Lala Retro Whipped Cream

Drunk Elephant Lala Retro Whipped Cream

Drunk Elephant Lala Retro Whipped Cream (reviewed here) nourishes skin with ceramides, cholesterol, fatty acids and humectants, and then seals them all in with six different tropical oils. A little goes a long way!

Best Lightweight: First Aid Beauty Ultra Repair BarriAIR Cream

First Aid Beauty Ultra Repair BarriAIR Cream

First Aid Beauty Ultra Repair BarriAIR Cream

First Aid Beauty Ultra Repair BarriAIR Cream has a unique "light as air," cream-to-foam texture. But it still works hard at repairing skin with ceramides, cholesterol and fatty acids (and no fragrance, allergens or irritants).

Best Oil-Free: Summer Fridays Cloud Dew Oil-Free Gel Cream

Summer Fridays Cloud Dew Oil-Free Gel Cream

Summer Fridays Cloud Dew Oil-Free Gel Cream

Summer Fridays Cloud Dew Oil-Free Gel Cream is one of the better options for acne-prone skin. Both oil-free and silicone-free, it combines hyaluronic acid, amino acids and ceramides in a non-greasy gel-cream.

Best Clean Beauty: The Nue Co. Barrier Culture Moisturizer

The Nue Co. Barrier Culture Moisturizer

The Nue Co. Barrier Culture Moisturizer

The Nue Co. Barrier Culture Moisturizer rebuilds your barrier with pre-, pro- and post-biotics, ceramides, nicinamide, squalane and Centella Asiatica extract. It's also free of fragrance and silicones.

Best K-Beauty: Pyunkang Yul Intensive Repair Cream

Pyunkang Yul Intensive Repair Cream

Pyunkang Yul Intensive Repair Cream

Pyunkang Yul Intensive Repair Cream combines an array of the best fatty acids with ceramides, amino acids, peptides and Korean botanicals. Although it's aimed at dry skin, it's not heavy, sticky or greasy.


Now you know what moisturizer really does to your skin—and what to look for, if you actually need one. 

As Dr. Peter Elias points out, "moisturizers can absolutely make skin worse. Some products can be incorrectly formulated, not only allowing moisture to escape but literally sucking it out of your skin."

With these guidelines, you'll be better equipped to select the right product, and avoid the wrong ones. 

And if you're still struggling with dryness, check out my tutorial on how to get rid of dry skin. Something else in your skincare routine could very well be the culprit!

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