70 SKIN MICROBIOME
Ethylhexylglycerin respects the microbiome
Matthias Hentz – Ashland Specialties, Germany
“Increased stress due to COVID-19 will draw more consumers to sensitive skin care products, which they believe are safer for skin”.1 The COVID-19 pandemic, and now its
variants, has focused the world’s attention on disinfectants and wash products. Prevention of contamination on the skin has never been more important to manufacturers and consumers. With an increase in hygiene measures, the skin may suffer. Dryness, redness, or irritation and more call for nourishing and caring routines to manage both possible contaminations and a healthy skin flora. It is therefore expected that ‘sensitive skin’ claims will gain high attention across regions. 1 The increased consumption of disinfectants
and cleansing formulas certainly has a negative influence on the skin flora. But how about ingredients that are designed to inhibit the growth of microorganisms to protect valuable products like cosmetics from deterioration and consumers from unwanted infections by pathogens? It could be assumed that these ingredients can have an influence on the microorganisms not only in the cosmetic product, but also on the skin microorganisms.
Microbiome The human skin is colonised by billions, mostly harmless microorganisms. This community is called skin flora, also known as the microbiome or microbiota, and is composed of different species in different quantities. The microorganisms do not only live on the skin, sometimes called a ‘living layer’ but also in deeper regions, for example in glands and on the
ethylhexylglycerin ■ alcohol + 1.0% EHG ■ alcohol in water■
ethylhexylglycerin - 1% phenoxyethanol - 1% propanol-1 - 10% propanol-2 - 10% ethanol - 10%
dipropylene glycol - 10% 1, 2 propylene glycol - 10%
0 0.5 test organism: pseudomonas aeruginosa, contact time: 1 min. Figure 1: Improved efficacy of alcohols in combination with 1% Ethylhexylglycerin (EHG).
hair shaft. Bacteria, fungi, and viruses are found on the skin as well as mites, tiny arthropods. The microbiome is highly individual for
every person and body site specific. It can be regarded unique like a fingerprint or the DNA code however the composition can change over time. These interpersonal and site-specific variations are determined by the chemical and physical skin parameters such as pH, moisture, temperature, and nutrients, for instance. Some microorganisms prefer oily, others moist and still others only like dry areas. Many aspects such as genetic, age, gender, environment, lifestyle, and personal care routines influence the skin parameters and therefore also the microbiome.2,3,4 Aside from personal care routines, it is
crucial to determine the influence of individual ingredients used in skin wash or care formulas. Antimicrobials are designed to inhibit the
growth of microorganisms to protect valuable products from deterioration and users from unwanted infections by harmful organisms. It could be assumed that those ingredients may have an influence on the microorganisms not only in the cosmetic product, but also on the skin microorganisms after application.
Ethylhexylglycerin – a multifunctional for personal care formulas While recent events have focused industry attention on antimicrobial actives, multifunctionals can be used to boost the efficacy of these materials, while adding other functionalities to a formulation. Ethylhexylglycerin, launched in 1991 (under Schülke & Mayr and recently acquired by Ashland), gave the personal care industry its first truly multifunctional additive. In the early 2000s the unique characteristics of this product started attracting the attention of formulators. Ethylhexylglycerin is widely known for its
ability to boost the activity of preservatives and antimicrobial actives. Early studies combining this material with short chain alcohols and glycols proved this synergy, offering a new way to boost preservative efficacy in finished formulation (Fig 1). In their patent granted in 2005, Modak,
drop 1: demineralized water drop 2: dm water
+1.0% phenoxyethanol/ ethylhexylglycerin
Figure 2: Contact angles of aqueous solutions. PERSONAL CARE September 2021 drop 3: dm water +0.9% phenoxyethanol
drop 4: dm water
+0.1% ethylhexylglycerin Theory - ethylhexylglycerin reduces interfacial tension on cell wall of organisms
Gaonkar and Sampath illustrate “synergistic combinations of Octoxyglycerin (former INCI designation for Ethylhexylglycerin) and at least one other antimicrobial agent in formulations which are more effective than prior art compositions without causing increased irritation to the skin of the average user”.5
This technology is of particular
interest today, as increased use of hand sanitisers by the public has increased the prevalence of dry, irritated hands. As little as 1%
www.personalcaremagazine.com 1 1.5 2 2.5 3 3.5 Reduction factor in log steps 4 4.5 5
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