Why are preservatives necessary?
As substances added to prevent spoilage due to microorganisms, preservatives are added in products such as food, cosmetics, and medicines to keep them from decomposition resulting from the proliferation of microorganisms or unwanted chemical changes.
Cosmetics are composed of water, oil, moisturizers, thickening agents, surfactants, and functional ingredients, as well as adequate levels of water and nutrients for microorganisms to live. In addition, cosmetics can be easily exposed to microorganisms when used with hands or devices, and the microbial contamination of cosmetics can cause microorganism-induced decomposition or alteration, and side effects in the skin or protective membranes due to microbial metabolites, which it makes it impossible to use cosmetics normally. Therefore, using preservatives is essential for the long-term protection of cosmetics from microorganisms. Preservatives added in cosmetics provide a long-term protective effect against microorganisms by suppressing the multiplication of microorganisms and even killing them upon the microbial contamination of cosmetics. Although the conventional parabens have widely been used as cosmetic preservatives, allergic responses to parabens and their accumulation in the human body have the potential to disturb the endocrine system and generate resistant bacteria. With the emergency of this issue, parabens are no longer used in South Korean cosmetics2). As this shows, although the controversy over the safety of preservatives has created constant needs for new and safe ingredients for preservatives, it is difficult to meet the requirements for their use in cosmetics. Accordingly, long periods of research and substantial efforts are needed to develop new preservative ingredients. Preservative ingredients for cosmetics should meet various conditions. For example, they should have a wide antimicrobial spectrum, be effective at low concentrations, ensure cost competitiveness and smooth supply, be easily applicable to cosmetic formulations, and maintain safety when cosmetics are applied to the skin4) (Figure 1).
Trend in the use of cosmetic preservatives
The latest trend in the cosmetics industry can be summed up as eco-friendliness/green, safety, and sustainability (Figure 2). In recent years, many consumers have increasingly pursued “good consumption” in which they pay attention to whether cosmetics production process and ingredients are eco-friendly, and they are safe and sustainable for both the skin and the environment through various sources of information before purchasing them. Until the early 2000s, parabens have widely been used as cosmetic preservatives, but with the emergence of their safety issues, parabens are no longer used in South Korean cosmetics. The removal of parabens in the market has increased the demand for new preservative ingredients to replace parabens and promoted the development of cosmetics based on the “paraben-free” concept. Accordingly, preservative ingredients such as phenoxyethanol and ethylhexylglycerin (EHG) have increasingly been used worldwide, including South Korea (Figure 3). Moreover, the expanding demand for the “no preservative system”, aimed at not using preservative ingredients registered for cosmetic preservatives, is increasing research and development on new alternative ingredients to traditional preservatives. Of them, the antibacterial effects of diols (R(OH)2), which had been used as moisturizers or solubilizers for cosmetics, began to be known, leading to the broader use of diols such as propanediol, pentylene glycol, hexanediol, and octanediol as alternative ingredients to traditional preservatives. In addition, cosmetic players have increased the adoption of natural preservative ingredients, such as various natural plant/herb plants, natural essential oils, and plant-derived organic acids, in order to actively reflect the growing consumer preferences for natural ingredients (Figure 4).
Natural ingredients for preservatives
Natural preservative ingredients are made of ingredients that naturally exist, including plant/herb extracts that are extracted from the leaves, roots, flowers, fruits, and seeds of plants in various ways, organic acids, protein-like antimicrobial peptides composed of 30 to 60 natural amino acids, as well as propolis and chitin that are extracted from nature1),6)12) (Table 1).
However, the natural preservative ingredients that have been developed to date have difficulties in their commercialization due to various problems, which include changing colors and scents, lowered stability, narrow antibacterial spectrums, problems in applying to formulations, inconsistent contents of active ingredients, no identification of active ingredients or medicinal actions, and high prices1).
Accordingly, Activon Co., Ltd have steadily developed alternative ingredients to not only synthetic preservatives, but also natural preservatives. The company has developed natural glycols that remedy the weakness of the conventional natural preservative ingredients, which are Natural 1,3-Propanediol (product name: Activonol-3), Natural Pentylene Glycol (product name: Activonol-5N (Natural)), and Activonol Green-GCP (Glyceryl Caprylate, Glyceryl Undecylenate, Pentylene Glycol)
The Natural 1,3-Propanediol and Natural Pentylene Glycol are natural ingredients that were developed through an eco-friendly process based on their already proven preservative effects and applicability to formulations through synthetic diols. They are safe for the skin and have obtained the COSMS certification.
The Natural 1,3-Propanediol (product name: Activonol-3) is produced from crude glycerol, a byproduct of bio-diesel, through an eco-friendly fermentation process. It is a natural preservative ingredient developed in step with the latest cosmetics trend of eco-friendliness/green, safety, and sustainability (Figure 5).
In addition, the Natural Pentylene Glycol (product name: Activonol-5N (Natural)) is a natural preservative ingredient with superior antibacterial effects to 1,3-Propanediol, coupled with moisturizing effects and applicability to various formulations. It generates antibacterial effects by penetrating into the cell membranes of bacteria (Figure 6).
It generates strong preservative effects when applied to various skin and hair care products at concentrations of 1.2% to 2.0%. According to the results of a skin irritation test, it exhibited no irritation at a concentration of 2.0% (Table 2).
Conclusion
Despite various issues such as safety, preservatives are essential for cosmetics. Although safer and more eco-friendly natural preservative ingredients continue to be developed in line with the latest trend of eco-friendliness/green, safety, and sustainability, there is difficulty commercializing natural preservative ingredients that fully meet the requirements for cosmetic preservatives.
Therefore, Activon Co., Ltd made up for the weaknesses of the existing natural preservative ingredients by developing Natural 1,3-Propanediol, Natural Pentylene Glycol, and the natural preservative ingredient Activonol Green-GCP.
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