Glycerin. The humectant that you’ve probably seen in most of your skincare products but never really stopped to think about. If hyaluronic acid is the show horse of the skincare world, glycerin is the quiet workhorse behind the scenes. Find out why this underrated skincare ingredient has been in cosmetics since the mid-1800s - and how glycerin is finally earning some long awaited recognition.

A walk through the aisles of your local beauty retailer will show you that skincare marketing is dominated by what’s trending. Hyaluronic acid is in every other product name or advertised somewhere on the packaging. If it’s not hyaluronic acid, it’s niacinamide.

But if you take the time to read the ingredients list on the back, you’ll notice that one ingredient appears again and again… glycerin. This humectant is the backbone of countless hydrating formulas - and for you science nerds, also the literal backbone of fats called triglycerides.

Glycerin is often referred to as glycerol in chemistry. The “-ol” ending lets us know it’s an alcohol, an organic compound that has a hydroxyl (OH) functional group in its chemical structure. These OH groups are also why this sugar alcohol is able to function as a humectant as they allow it to interact with water molecules via hydrogen bonding.

Humectants are ingredients that are able to attract and hold onto water, something we refer to as hygroscopicity. Used in skincare, they keep water in the skin that would be lost through evaporation - increasing skin hydration as a result. In order for an ingredient to function as a humectant though, it needs to meet certain criteria.

1. Cosmetic humectants need hydroxyl or amino groups in their structure in order for hydrogen bonding to occur with water.
2. They also need to have enough of these groups within their structure so that the molecule is polar3
3. Effective humectants also need to be substantive, meaning they remain on the skin surface and do their job unlike volatile ingredients that evaporate 4

Glycerin has three OH groups that allow it to attract water. Being a polar molecule, it’s also hydrophilic - it can interact with water, including dissolving in it. Water-soluble ingredients usually have a tough time getting into the hydrophobic skin barrier as it’s designed to repel water. Because it’s so small though, weighing in at about 92 daltons, glycerin is able to penetrate. 

Glycerin is also considered a skin identical ingredient, meaning it’s naturally found within our skin. Not only are skin reactions to glycerin rare but our skin is more likely to react positively to ingredients it knows what to do with. Our skin has its own natural humectants within the skin cells of the skin barrier, referred to as the Natural Moisturizing Factor (NMF). These humectants are composed of hyaluronic acid, urea, amino acids, sodium PCA, lactic acid, and glycerin.

Within our skin, we also have proteins called aquaporins that help transport water and solutes like glycerin. Aquaporins are important for moving water into the skin and alongside glycerin, maintain skin hydration5. It’s believed that topical glycerin in skincare may be transported by these aquaporins too and that the application of glycerin can be helpless for dry skin resulting from aging or skin disorders where we see lower levels of aquaporins.

Why Use Glycerin?

We’ve already discussed how glycerin is a fantastic hydrator. It’s better researched than hyaluronic acid and has a longer history of use, even performing better in some comparison studies. 

From a brand formulation standpoint, glycerin is attractive for two main reasons: it’s highly reliable and doesn’t break the bank. It doesn’t change the odor or color of the formula, it’s well tolerated, and it’s versatile and able to be used in a wide variety of formulations. It also delivers in terms of customer experience as products with glycerin provide an immediate hydrating and skin softening effect.

Glycerin has a number of applications, including:

• Can be used as an OTC skin protectant at concentrations 20-45%
• As a humectant in serums and moisturizers
• Added to offset irritancy and dryness during cleansing 
• Smoothing and softening in haircare 

While glycerin can be used in high concentrations without causing irritation or a high cost, it does have one downside: stickiness.  For this reason, you’ll often see it limited to 5% in leave-on products unless it’s been carefully formulated to reduce the sticky feel.

What to Look for in Skincare

Chances are, it’s already in your routine. In fact, it’s in every Stratia Skin product that contains water from the Rewind serum, to the moisturizer, to the Velvet Milk Cleanser - it’s that great. But in a blog dedicated to giving glycerin the credit it deserves, let’s talk about where it can really shine and how to maximize its results.

There’s 2 approaches I love to see with glycerin.

1. high concentration glycerin formulas that take advantage of its skin protecting and barrier supporting benefits while formulating around the stickiness 
2. well rounded glycerin products that surround it with ingredients that complement its effects.

High Content Glycerin Products  

There’s a few different ways to tackle the issue of stickiness but we’re seeing some newer formulas that utilize a glycerin based gel using polymers with emollients like squalane or silicones for smoother application. Another option is to use high concentrations of glycerin in a wash-off product like a cleanser. The end product features the higher concentrations of glycerin known to have skin protectant* and barrier boosting abilities while still applying nicely

*as this is a drug claim, a brand would need to meet all requirements for OTC skin protectants including labeling in order to say their product is a skin protectant

Well-Rounded Glycerin Products

The Stratia Skin line includes a number of examples of how glycerin can work even better within the right formula.

• Velvet Cleaning Milk. Glycerin is with skin soothers to further reduce irritancy during cleansing alongside a low pH and mild cleansing agents.
• Lipid Gold. Glycerin offers immediate hydration alongside other humectants while ceramides and other barrier replenishing lipids decrease water loss from the skin over time. 
• Rewind Serum.  High molecular weight hyaluronic acid is film forming and traps water in the upper skin layers while glycerin goes deeper. Niacinamide acts as a ceramide promoter to boost barrier function while N-acetyl glucosamine is a precursor for hyaluronic acid. Panthenol, allantoin, and other humectants further hydrate the skin, smooth roughness, and sooth the skin.

References 

Mira is a skincare educator, blogger, and the content creator behind Skin Science by Mira and The Skincare Forum on Facebook. While skincare keeps her busy, she’s also pursuing her degree in Nursing and loves to spend her free time hiking.  As a content writer for Stratia Skin, Mira shares her evidence-based approach to skincare topics and a passion for making science accessible.