What is glycerin?
Glycerin is "a thick, sweet, clear liquid used in making medicines, food, soap, etc."1 When an alkali – typically sodium hydroxide or potassium hydroxide – is added to a fatty ester or triglyceride, a chemical reaction called saponification occurs, which creates the byproducts of soap and glycerin.

Glycerin is used as a solvent in traditional herbal remedies (botanical extracts called glycerites) and as a strong humectant and emollient in skin care, hair care, and personal care products. In addition to its humectant properties, glycerin gently conditions the skin and leaves a silky-smooth finish, as long as it is used at less than 25 percent concentration. While higher concentrations are attractive in theory (50 percent or higher actually inhibits microbial growth), it results in a sticky, syrupy feel on the skin rather than a soft, smooth, and silky feel.

Skin benefits of glycerin
Glycerin comes with many skin benefits and has been studied for easing symptoms of eczema, dry skin, and even psoriasis.2,3,4 Most inflammatory or irritant skin conditions benefit from high quality vegetable glycerin due to its known wound-healing properties and important role in skin cell maturation.5
Its gentle cleansing action is great for drier, more sensitive skin types because it does not strip the skin's natural lipids the way soaps – even natural castile or black soaps – and foaming agents – even gentle amphoteric or non-ionic surfactants – can. It is also desirable because it has a fairly neutral pH, typically 6 or 7, that is much closer to the skin's naturally acidic pH than alkaline soaps and surfactants.

Because it has the unique benefit of having both humectant and emollient properties, glycerin is also excellent for not only bringing more moisture into the skin, but also helping it stay there, maintaining appropriate skin hydration levels, and helping to prevent transepidermal water loss.

Various sources of glycerin
As with many skin care ingredients, there are multiple sources of glycerin. Not all glycerin is created equal or offers the same skin benefits. Glycerin that has been derived naturally from the saponification of organically sourced plant or animal fat is a healthy and beneficial ingredient for the skin. However, much of the glycerin on the market comes from the process of distilling petroleum, therefore creating propylene glycol, which poses environmental risks, as well as potential skin irritation with frequent exposure.6

Even "natural" glycerin can be heavily refined and contaminated with diethylene glycol, ethylene glycol, or other undesirable compounds that may contribute to skin irritation and toxic chemical body burden.

Glycerin can also be derived from the process of creating biodiesel fuel by adding methanol to a lipid. Furthermore, much of the "vegetable glycerin" on the market is derived from GMO soy, which most people seek to avoid. Unless people know where and how their product manufacturer sources their glycerin, they will not know the type of the fat or oil used (whether natural, organic, GMO, or synthetic), the alkali, what the process was to obtain the glycerin, or what else is processed at the same facility that might pose risk of contamination.

Glycerin-labeling considerations
First of all, look for product labels that state that the products contain non-GMO vegetable glycerin. It is not enough to just look for the words "natural," organic," or "non-GMO" on the front of the packaging, in the marketing materials, or on the company's website. Clients need to check the full ingredient deck on the back of the label. Though the FDA and FTC have recently begun to pay more attention to words used on skin care labels and what claims are made, oversight has only just begun to take place. Many companies still use misleading or non-transparent wording and placement of the words, as well as confusing practices, such as angel dusting and greenwashing.

If a product is labeled with "glycerin" or "vegetable glycerine," visit the company website to determine the ingredient's source. It may be necessary to contact the company or place a call directly to obtain this information.

Professionals may also see products that contain glycerin that do not actually use the words "glycerin," "glycerol," or "vegetable glycerine" on the label. Instead, the glycerin is indicated on the label similar to how castile soap is labeled: with the fats and alkali listed out separately. Example: Organic coconut oil, potassium (or sodium) hydroxide, organic jojoba oil, organic olive oil. This labeling practice is allowed and truthful, though it might be confusing to even label-savvy professionals and consumers.

DIY caution
Today, more than ever, aestheticians are creating their own signature products and services to offer their clients a truly personalized experience. Glycerin is a popular DIY skin care ingredient, both for the purpose of making gentle herbal extracts and also in making custom back bar treatments and retail products. While glycerin is shelf stable and does not require preservation or refrigeration in concentrations above 50 percent, it is important to know that using any concentration less than 50 percent poses several challenges.

Because of its strong humectant properties, lower concentrations of glycerin – in conjunction with other possible ingredients in the formulation – raise the product's water activity and promote microbial growth in the product. This action makes these products unstable and at risk for growth of gram-positive and gram-negative bacteria, mold, and yeast, and, therefore, require the addition of a strong broad-spectrum preservative. Most professionals who make their own products and treatments do so with the intention of offering a more natural experience to their clients. While there are natural preservation systems on the market, they require specialized training and testing for proper use. Even so, many humectant-containing natural products are very hard to properly preserve. It is not impossible, but it should not be attempted without first obtaining continuing education in natural product formulation and preservation.

Glycerin is a versatile ingredient with a multitude of skin benefits and very little risk of irritation or allergy – when sourced ethically. It is an excellent ingredient to look for in products the spa carries; it is also a great idea to keep some on hand in the spa to use in customized products or treatments. It is fairly inexpensive to purchase in bulk and remains shelf stable on its own for an extended period of time, without need for refrigeration. Just know the source of any glycerin the spa buys or sells and its clients' skin will rejoice!

• Bon Vital Bon Vital
• Circadia by Dr. Pugliese Circadia by Dr. Pugliese
• DMK-Danne Montague-King DMK-Danne Montague-King
• Dermatude Dermatude
• ECHO2Plus ECHO2Plus
• Eve Taylor North America Eve Taylor North America
• ExPürtise ExPürtise
• GR8/SKN GR8/SKN
• Glo Skin Beauty Glo Skin Beauty
• Janssen Cosmetics Janssen Cosmetics
• Le Mieux Le Mieux
• LE’VEA LE’VEA
• Meg21 with Supplamine® Meg21 with Supplamine®
• Nature Pure Labs Nature Pure Labs
• Rhonda Allison Cosmeceuticals Rhonda Allison Cosmeceuticals
• Shunly Skin Care LLC Shunly Skin Care LLC
• Skin Blends LLC Skin Blends LLC
• Skin Script Skin Care Skin Script Skin Care
• Skinprint Skinprint
•  

References
1. Webster, M. (2016, August 2). Simple Definition of Glycerin. Merriam-Webster Learner's Dictionary.
2. (2008, January 21) Skin Pharmacol Physiol.
3. Short, R. W., Chan, J. L., Choi, J. M., Egbert, B. M., Rehmus, W. E. and Kimball, A. B. (2007), Effects of moisturization on epidermal homeostasis and differentiation. Clinical and Experimental Dermatology, 32: 88–90.
4. Tremblay, MSc Sylvie. (2015, October 8) Sources of Glycerine. Livestrong. Leaf Group.
5. (2003, December 3) Medical College Of Georgia. Glycerin May Help Skin Disease, Study Finds. ScienceDaily.
6. (2015, January 21). Toxic Substances Portal - Propylene Glycol. Centers for Disease Control and Prevention.

Rachael Pontillo is the bestselling author of Love Your Skin, Love Yourself, and co-author of the cookbook, The Sauce Code. She is an award winning AADP board certified holistic health and image coach, certified metaphysical practitioner, licensed aesthetician, natural skin care formulator and educator. She is the creator of the popular blog and lifestyle site, www.holisticallyhaute.com, and the six-week online course, Create Your Skincare™. Pontillo is a recipient of the Institute for Integration®'s esteemed Health Leadership Award and is also a brand ambassador and spokesperson for NeoCell™. Pontillo is currently working towards a Ph.D. in Holistic Life Counseling.