UNDERSTANDING THE DIFFERENCE
If you peruse the ingredients list of any personal care product on your bathroom shelf, chances are you’ll come across propylene glycol. Its presence in skincare is ubiquitous, but its functions, safety, and sourcing are often shrouded in ambiguity.
The confusion likely stems from the fact that propylene glycol (sometimes listed as 1,2-propanediol) seemingly does it all, across a variety of product categories – it’s a humectant, emollient, texture enhancer, and preservative. It’s defining feature is that it acts as a formative part of a nourishing base, evenly dispersing ingredients and giving products a luxurious texture. As a result, it’s a go-to raw material for many cosmetic chemists formulating velvety, hydrating products.
Conscious consumers become even more bewildered when they see propylene glycol listed in nearly all their “clean” personal care products and try to reconcile its omnipresence with the EWG’s Skin Deep Cosmetics Database rating of 3 (fair). In the last few years, scientists have discovered how to synthesize a plant-derived propylene glycol, which CORPUS uses. Due to its novelty, bio-based propylene glycol has yet to find its way into many products on the market. As a result, global research and advocacy groups, like the EWG, have yet to address the differences between traditional propylene glycol and the renewable raw material of the same name that are used in CORPUS formulations. While propylene glycol’s safety in personal care has been demonstrated across thousands of products, there exists growing demand from consumers that ingredients should not only be safe and effective, but also eco-conscious. In the coming years, the EWG and others will begin to define their differences – making it clear to consumers that despite sharing a name, these ingredients are worlds apart.
WHAT IS BIO-BASED PROPYLENE GLYCOL?
Historically, propylene glycol was made from petrochemicals, more specifically from propylene oxide. But recent developments in green chemistry have pioneered a plant-based version that is derived from vegetable oils. Via a process called hydrogenolysis, glycerin and hydrogen react at high temperature and pressure to produce an entirely bio-based propylene glycol. While these two versions of propylene glycol serve the same function in a final product and are chemically identical, they are made from very different materials. Perhaps the best analogy is that of hiking up a mountain. It’s possible to take different routes to the same summit, as is the case with creating propylene glycol.
WHAT IS THE SUSTAINABLE CHOICE?
You might ask yourself, well if they are the exact same ingredient, what is the benefit of using bio-based propylene glycol? The answer lies with CORPUS’ commitment to sustainable and transparent sourcing. Each year, it is estimated that more than seven million barrels of oil are used to produce traditional propylene glycol. CORPUS’ bio-based propylene glycol is produced from renewable, low-carbon feedstocks, like corn and sugar cane. It also provides a 61% reduction in greenhouse gas emissions when compared to propylene glycol derived from petrochemical production. Going with bio-based propylene glycol is an easy choice for CORPUS – it decreases our culture’s reliance on oil and has a much lower carbon dioxide impact than its petroleum-based counterpart. Raw material source matters.
IS IT "NATURAL"?
While the raw materials used in the manufacturing of bio-based propylene glycol are naturally sourced, propylene glycol itself is not referred to as “natural” because it undergoes a transformation from one chemical to another. While bio-based propylene glycol may not be naturally occurring, it is composed of one hundred percent bio-based carbon content. If you’re curious about how CORPUS defines “natural,” read more here.
IS IT DANGEROUS?
Propylene glycol is safe when used properly in personal care formulations. Reputable research organizations, like The Cosmetic Ingredient Review Board, assert that propylene glycol as it is commonly used in personal care does not pose consumer health risk. During the product development process, CORPUS performs a clinical primary skin irritation evaluation (PI test), which concludes that there is no potential of dermal irritation from the products.
There are some myths circulating in the clean beauty discourse that propylene glycol is unsafe because it enhances dermal penetration and is a skin sensitizer. Firstly, dermal absorption through the skin should not be a concern as it is negligible and turns into lactic acid or gets flushed out when urinating. Propylene glycol also has the FDA-backing of Generally Recognized As Safe (GRAS) as a food additive. That’s right, you can eat it. Secondly, the risk of propylene glycol causing dermal irritation is extremely low when it is applied in proper concentration on healthy skin.
THE BOTTOM LINE
In assessing all the available data, CORPUS believes that its bio-based propylene glycol is a wholly safe and more sustainable alternative to its petrochemically derived twin.
On an ingredients list, we find what are called INCI names. INCI names are internationally recognized titles used to identify cosmetic ingredients. While there are certainly benefits to having a uniform naming system, consumers are not granted total transparency with an INCI name alone. Currently, an INCI name, like propylene glycol, tells you nothing about the quality, sustainability, or source of an ingredient. As more innovative ways of producing ingredients are elucidated and the resulting novel raw materials find their way into products, it is likely that the International Nomenclature Committee (INC) will evolve their identification standards. It’s possible (and CORPUS remains very hopeful) that “bio-based propylene glycol” might appear on INCI lists in the not-too-distant future.
By Leigh Winters, Neuroscientist & Holistic Wellness Expert