As I was researching current literature and sourcing scientific papers on the link between our gut and skin microbiomes, their influence on our brain and subsequently our mood for The Lab article “Could your skincare be affecting your mood?” One of the research papers I referenced was; The impact of skin care products on skin chemistry and microbiome dynamics. In this paper the authors demonstrated that molecules in commercial skincare persisted on the skin for weeks after application despite showering, swimming or spending time in the ocean. Their conclusion “Thus, a single application of some of these products has the potential to alter the microbiome and skin chemistry for extensive periods of time.” In this study they calculated that Polyethylene glycol (PEG) had a half-life of 0.5 weeks. This means that 1/2 the concentration of polyethylene glycol applied was still present 0.5 weeks after application and persisted for up to 2 weeks. Propylene glycol lasted on the skin for up to 3 weeks and had a 1/2 life of 1.9 weeks.

How long a compound persists on the skin is consistent with its hydrophilic or hydrophobic properties, meaning that water soluble compounds wash out more quickly but still remained. Until this study was completed in 2019 “no study has yet tested how susceptible the skin chemistry and microbiome are to alterations in the subjects’ personal care product routine.”

The key findings from this study are;

• Personal care product ingredients can remain on the skin for weeks after use, despite daily showering, swimming or spending time in the ocean and influence the skin chemistry and the skin microbiota* composition.
• Personal care products alter the molecular chemistry and bacterial diversity of the skin.
• Skin chemistry and bacterial diversity changes are product, skin site and person. specific and observed from the first week of use.
• Applying a personal care product to one region of the skin will likely affect other skin regions.
• Despite the widespread of personal care products their impact on the molecular chemistry and microbiological composition of the skin is very poorly studied and understood.

What exactly is PEG (polyethylene glycol)? Where does it come from? Why is it used in commercial skincare?

Polyethylene glycol is a synthetic polymer derived from petroleum, natural gas or coal in a process call ethoxylation from highly toxic ethylene oxide and ethylene glycol (antifreeze) or water. A by-product of ethoxylation is 1,4 dioxane a likely human carcinogen and traces can remain in the final product. I searched *INCIdecoder website for PEG https://incidecoder.com/search?query=PEG&activetab=ingredients it resulted in 10 pages of PEG based cosmetic ingredients. Because of the chemical properties of PEG, it is easily reacted with other chemicals to form additional synthetic chemicals. Cosmebio https://www.cosmebio.org/en/reports/PEG-ingredient-cosmetics-you-should-avoid/ estimates that there are more than 600 different chemicals in this family of ingredients used in cosmetics.

"PEGs are used in cosmetics “as is” or in combination with their derivatives in which their 2 terminal primary hydroxyl groups can create mono-, di- and poly-esters, amines, ethers and acetals. Furthermore, PEGs can create additional compounds and complexes through a reaction in their ether bridges. Overall, PEG derivatives may include PEG ethers (e.g. laureths, ceteths, ceteareths, oleths, and PEG ethers of glyceryl cocoates), PEG fatty acids (e.g. PEG laurates, dilaurates, stearates, and distearates), PEG castor oils, PEG amine ethers (PEG cocamines), PEG propylene glycols, and other derivates (e.g., PEG soy sterols and PEG beeswax).” Safety Evaluation of Polyethylene Glycol (PEG) Compounds for Cosmetic Use.

The authors of this study, published in Toxicological Research June 2015 noted “all PEG compounds were not covered in the previous studies due to their wide variety, and the introduction of new entities currently used in cosmetics suggests supplementary evaluation. Thus, it is essential to continuously monitor the safety and risks of PEG-derived products being exposed to consumers using cosmetic products to ensure that no potential health threats will arise, especially when used extensively and chronically.”

Gert -Jan M Gruter in the review, Using carbon above the ground as feedstock to produce our future polymers, “5–6% of all oil is used as feedstock to produce plastics” this includes ethylene and propylene.

Because PEG can range from liquid to solid dependent on the repeating ethylene glycol units and molecular weight, PEG is used in a diverse range of industries including textiles, pharmaceutical, medical equipment, automotive, paint, plastics, food & beverage as an additive (E1521) and in food packaging, chemical manufacturing as a solvent, dispersant and lubricant and many more industries and applications. It is estimated that the polyethylene glycol market size was valued at USD 3279.9 million in 2023 https://www.marketgrowthreports.com/global-polyethylene-glycol-market-27905366 with an estimated market size of 2750 thousand tonnes in 2022 Chemanalyst

PEGs are used in skincare as a surfactant, emulsifier, thickener or gelling agent for viscosity adjustment, solvent, penetration enhancer, dispersing agent and filler. Properties all related to product attributes rather than skin functional needs. They are used because of their effectiveness in the chemical formulation and low cost rather than for skin benefits. Versatility of PEG chemical properties means that they are found in a exhaustive range of personal care products; shampoo & conditioner, hairspray, toothpaste, mouthwash, skincare, make-up, shaving cream, deodorant, soap. It is estimated that 8% of the global production of polyethylene glycol is used in personal care category in 2022 https://www.chemanalyst.com/industry-report/polyethylene-glycol-market-2877

PEGs are huge family of synthetic chemicals using the petroleum-based polymer of polyethylene glycol that are used in skincare for product attributes with the possibility of contamination with highly toxic ethylene oxide and by-product 1,4 dioxane, a likely human carcinogen. Google the ingredients of skincare moisturisers and creams, cheap and very expensive and you will find PEG- or several in the ingredients list. PEG is used in machinery as a lubricant, reducing friction and has moisture binding affinity effectively removing water from the environment, meaning it feels nice on application but removes water from your skin and can remain on the skin for up to 2 weeks post use altering the skins chemistry and microbiome.

Your skin is a nature designed system it needs nature designed skincare. Skincare that is grown, not chemically engineered in an oil refinery from non-renewable petroleum. Pegs are for the clothes line NOT skincare, even then they should be stainless steel or wooden not plastic. By the way check your laundry powder or liquid, PEGs are probably there as well.

Note, check all personal care products for PEGs, infuriatingly skincare brands using PEG ingredients claim natural. Remember crude oil is natural and there is no legislation governing the use of the word natural whereas naturally occurring has a legal definition. Vitis V Face TonIQ is naturally occurring. Its not ethical but its not illegal even though PEGs are a fully synthetic chemical compound. PEGs are prohibited in organic cosmetics.

https://cen.acs.org/business/consumer-products/companies-getting-14-dioxane-home/98/i11

Using carbon above the ground as feedstock to produce our future polymers

https://efsa.onlinelibrary.wiley.com/doi/full/10.2903/j.efsa.2018.5293

*Microbiota describes the living microorganisms found in a defined environment. Microbiome refers to the microorganisms in the environment and their metabolites.

**INCI International Nomenclature Cosmetic Ingredient. Personal care products are to list ingredients in descending order to 1% using INCI naming convention. After 1% the ingredients can be in any order excluding colour which must appear last and 82 fragrance allergens must be declared on the label if concentration in the product exceeds 0.001% in leave on products i.e. moisturiser and 0.01% in rinse off products