SKIN MICROBIOME
Ethylhexylglycerin incorporated into an alcohol- based hand sanitiser formulation can boost the antimicrobial efficacy, while improving the moisturisation of the skin after use. The surfactant structure of
Ethylhexylglycerin has been proposed to be one of the mechanisms that allows this material to boost preservative activity. As Ethylhexylglycerin has been shown to significantly reduce surface tension, it has been theorised that this multifunctional additive reduces the interfacial tension on the membrane of microorganisms, allowing other antimicrobial materials to penetrate faster and more effectively (see Fig 2).6 This surfactant characteristic may be the
reason that Ethylhexylglycerin has been shown to improve fragrance fixation on skin. An internal study, evaluating the effect of this material on fragrances, shows that Ethylhexylglycerin has a boosting or fixating effect on many fragrance components, while producing a fresher or softer scent with others. This ability to bind certain oily substances to the skin might prove beneficial for other formulation components, such as organic sunscreens or lip stains. Examining the structure of
Ethylhexylglycerin more closely, points to it being a medium-spreading emollient:
C4 H9 -CH-CH2 C2 H5 -O-CH2 -CH-CH2 OH
skin-feel of various personal care formulations was demonstrated in a 2010 study.7
The ability of this material to improve the In this
study, a panel of trained subjects were asked to rate the feel of two cream formulas containing a high level of glycerin; one containing 1% Ethylhexylglycerin and one with no Ethylhexylglycerin. The results showed the product containing the Ethylhexylglycerin to feel less tacky and less greasy, with improved penetration and lower soaping. These results can be extrapolated to the use of Ethylhexylglycerin to improve the feel of other formulation ingredients, such as certain sunscreen actives, known to cause tackiness. Further early studies into the efficacy of
Ethylhexylglycerin also support the use of this material as a substitute for triclosan in deodorant products. In a 1998 study, deodorant formulations containing Ethylhexylglycerin were compared to ones containing triclosan. The formulations containing Ethylhexylglycerin and triclosan showed statistically similar odour reduction in sniff tests on 20 volunteers. However, testing on several gram-positive organisms commonly found in the axilla region, proved that Ethylhexylglycerin has minimal effect on the microbiome as compared to triclosan, which indiscriminately eliminated all microorganisms, even at low concentrations.8 In other testing, Ethylhexylglycerin was shown to be effective against Micrococcus sedentarius, a common cause of foot odour.
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10 9 8 7 6 5 4 3 2 1
-OH Ingredient name cinnamyl alcohol aldehyde C-10 (decanal)
aldehyde C-16 (ethyl methylphenylglycidate)
citral* citronella
hydroxycitronellal* cinnamal*
musk ketone* diphenyl ether citronellol* linalool*
alpha-terpineol amyl salicylate anethole
benzyl acetate
Isobornyl acetate linalyl acetate
linalyl isobutyrate menthanyl acetate methyl anthranilate caryophyllene amande amère niaouli
patchouli brun hulle essence
*76/768/EEC Article 6 (1) (g) substance X = enhancement of the scent by ethylhexylglycerin Boosting: enhancement of the scent after 1 hour. Fixating: enhancement of the scent after 6-24 hours
Figure 3: List of respective perfuming ingredients.
Ethylhexylglycerin improves the overall impression of a cream. Also tested: ■ reduces tackiness ■ increased speed of penetration ■ reduced soaping ■ reduced greasiness
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✘ ✘ ✘ ✘
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Boosting ✘ ✘
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Fixating ✘ ✘
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Fresher scent Softer scent
71
Ø = 2.95 Ø = 2.05
0 =very good 10 =very bad
without Ethylhexylglycerin ■ with 1% Ethylhexylglycerin■
Figure 4: Panel results on skin feel with and w/o Ethylhexylglycerin.
Stabilisation of Ethylhexylglycerin Many organic substances undergo oxidative degradation reactions. Specifically, ethers have the potential of forming peroxides if exposed to air. This is also a concern for polyether, like ethoxylated surfactants, as has been reported in the past. 9, 10, 11 Several different breakdown products
can be expected from primary oxidation reactions, like alcohols, ketones, aldehydes, and carboxylic acids. All these categories of substances are reactive enough to undergo secondary reactions which each other.
Additionally, 1,2-diols undergo oxidative cleavage reactions, known as glycol cleavage. Ethylhexylglycerin is a glycerol ether which
bears both functional groups, ether, and diol. This very fact makes it sensitive to ageing reactions under the influence of oxygen. To keep this purity for the entire shelf-
life, we developed a protection technology utilising stabilisers, like antioxidants. 12 As incompatibilities with the skin, such as irritations and sensitisation, are the most threatening side effects of the use of cosmetic products, stability of the raw materials, as well
September 2021 PERSONAL CARE
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