With the rise of products making microbiome-related claims in the cosmetics industry, formulators have been challenged with the task of creating products that keep the natural skin flora intact and healthy, while at the same time guaranteeing a formula that can resist spoilage on the shelf and in consumer hands.
These formulations with probiotic, prebiotic and post-biotic ingredients are expected to maintain or improve but never harm the skin flora. Some of the more classic preservatives that are traditionally used in cosmetics are broad-spectrum biocidal ingredients. While there are only very few conclusive studies on the effect of preservatives on the skin microbiome, it is anticipated that harsher, broad-spectrum biocides may have a bigger impact on the skin than molecules that are less potent or require additional ingredients to help achieve product protection (1).
This means that, while on one hand we would like to inactivate the organisms that accidentally enter the product, on the other hand we prefer to maintain the healthy, normal flora of the skin; a seemingly impossible task. While some products with living probiotics avoid chemical preservation altogether and instead rely on sterile, single-use packaging or refrigeration, this approach may not be suitable for the mass market.
In recent years, multifunctional ingredients have become more popular for protection of cosmetic formulations. Regulatory pressure and negative press on certain chemistries have limited the palette of preservatives that manufacturers want to see on the INCI label of their products. Molecules such as 1,2-Alkanediols (like 1,2-Pentanediol, 1,2-Hexanediol & 1,2-Octanediol), Hydroxyacetophenone, and Ethylhexylglycerin have become popular among new launches according to the Mintel GNPD database (2).
Symrise is a key-player in the field of multifunctional ingredients, which do not only aid in the protection of products, but also bring a multitude of benefits, for example moisturization and anti-oxidant capabilities. These multifunctionals are best used in smart combinations, which will allow them to be used to protect formulations.
We have shown that the use of a patented smart combination of 1,2-Alkanediols (1,2-Hexanediol and Caprylyl Glycol, Trade name: SymDiol® 68) alongside the antioxidant, Hydroxyacetophenone (Tradename: SymSave® H) can help protect a variety of formulations, like emulsions, wet wipes and rinse-off products. We tested this combination of ingredients in an emulsion containing Symrise’s ingredient Lactobacillus Ferment (Tradename: SymReboot® L19), which is a processed probiotic with full structural efficacy.
Using the forearms of healthy volunteers, we have been able to study the impact on such a formulation on the skin biome in vivo. The emulsion containing the two ingredients, plus the post-biotic, was applied to the skin twice a day for two weeks. The 16s rRNA genome of the skin surface was sequenced before and after the use of the emulsion. The results can be seen in the chart below. For the purpose of the study, the rRNA of the post-biotic ingredient was neglected.
The results clearly show that the pre-study microbiome composition has not been disturbed by the application of the two multifunctional ingredients, SymSave® H and SymDiol® 68. These ingredients, if used alone or in combination, are the perfect product protection system for a cosmetic formula that is looking to maintain the natural flora of the skin.
- Qian Wang, Shumei Cui , Li Zhou, Keke He, Liya Song, Haiyan Liang, Congfen He, J Cosmet Dermatol, 2019 Apr 18 (2) : 652-658, Effect of cosmetic chemical preservatives on resident flora isolated from healthy facial skin
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