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Antimicrobial Ingredients as Preservative Booster and Components of Self-Preserving Cosmetic Products

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This review reports cosmetic ingredients with antimicrobial activity including synthetic and natural (plant and microbial) origin as alternative for preservatives used in cosmetics as well described mechanism of their action.
Current Microbiology (2019) 76:744–754
1 3
Antimicrobial Ingredients asPreservative Booster andComponents
ofSelf-Preserving Cosmetic Products
Received: 16 October 2017 / Accepted: 10 April 2018 / Published online: 12 April 2018
© Springer Science+Business Media, LLC, part of Springer Nature 2018
This review reports cosmetic ingredients with antimicrobial activity including synthetic and natural (plant and microbial)
origin as alternative for preservatives used in cosmetics as well described mechanism of their action.
The preservatives are added to cosmetics to maintain their
microbiological purity during manufacture, packing, stor-
age, but especially during the entire period of use ensure the
safety of users. Despite the fact that preservatives are usu-
ally used in small concentrations, they are considered as one
of the main factors causing allergies to users [5]. Preserva-
tives, including formaldehyde and formaldehyde releasers,
isothiazolinones, iodopropynyl butylcarbamate, parabens,
thimerosal and triclosan may cause of allergic and irritant
contact dermatitis, and there are increasing evidences that
some of them may even cause toxic effects [35]. Moreover,
it is very disturbing that some preservative-resistant bacte-
rial strains isolated from cosmetic products show a degree
of cross-resistance with antibiotics [74]. One approach to
minimizing these effects is the use of preservative booster
or create self-preserving (preservative-free) cosmetic for-
mulations. Preservatives boosters are defined as cosmetic
ingredients with antimicrobial properties, which can signifi-
cantly reduce the concentration of synthetic preservatives
used in cosmetic products. Moreover, preservative boosters
show not only antimicrobial activity but also many of them
showed other desirable properties useful in cosmetic prod-
ucts (e.g. moisturizing, antioxidant etc.). This review reports
cosmetic ingredients with antimicrobial activity including
synthetic and natural (plant and microbial) origin for reduc-
ing or eliminating the amount of synthetic preservatives
described in Annex V of European Regulation for cosmetics
EC 1223/2009 in cosmetic formulations as well described
mechanism of their action.
Search Strategy
The PubMed, Scopus and Google Scholar databases were
searched for articles published from 1990 to the present.
Search terms included: “antimicrobial ingredients in cosmet-
ics”, “preservative booster”, “self-preserving cosmetics” and
“preservative-free cosmetics”.
Inclusion andExclusion Criteria
Selection criteria included articles that examined antimicro-
bial ingredients as preservatives booster and components
of self-preserving cosmetic products. Other than cosmet-
ics products (pharmaceutical products, food products) were
excluded from the study. Articles described antimicrobial
effectiveness of preservatives booster in cosmetic formula-
tion confirmed only by challenge test were included. Articles
described antimicrobial activity tested in disc diffusion or
microdilution methods were excluded. Articles in languages
other than English were excluded.
Synthetic Preservative Boosters
Appropriately selected synthetic ingredients with antimi-
crobial activity enable decrease or eliminate the use of pre-
servatives in cosmetics formulation are described in Table1.
* Anna Herman
1 Faculty ofCosmetology, The Academy ofCosmetics
andHealth Care, Podwale 13 Street, 00-252Warsaw, Poland
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... Conservantes ou sistemas conservantes são agentes antimicrobianos adicionados em formulações não-estéreis com o objetivo de impedir o desenvolvimento e multiplicação de microrganismos infecciosos que podem colocar em risco a integridade da saúde humana e também a estabilidade da formulação [2,3]. Os conservantes são utilizados em concentrações mínimas, a fim de minimizar os possíveis efeitos de toxicidade ao organismo humano. ...
... Os conservantes são utilizados em concentrações mínimas, a fim de minimizar os possíveis efeitos de toxicidade ao organismo humano. Essa pequena quantidade pode ser responsável pela indução da resistência, levando a uma tolerância dos microrganismos contaminantes de produtos cosméticos [1]; além disso, são responsáveis por desencadear reações alérgicas nos consumidores [3]. ...
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Após relatos de reações adversas e desregulação endócrina causada por alguns conservantes como os parabenos, amplamente utilizados em formulações tópicas e medicamentos, a indústria cosmética e farmacêutica enfrenta a falta considerável de agentes antimicrobianos com menor toxicidade, desencadeando o interesse na busca pelo desenvolvimento de novos sistemas conservantes seguros e eficazes. Substâncias naturais com amplo espectro de atividade antimicrobiana são alternativas interessantes para a pesquisa de novos conservantes. As micocinas são substâncias naturais produzidas por leveduras killer, que possuem potencial de inibir bactérias e fungos com amplo espectro de ação, baixa toxicidade e baixa probabilidade de indução de resistência microbiana. O objetivo deste trabalho foi de verificar a atividade conservante de micocinas produzidas por Wickerhamomyces anomalus quando incorporadas em gel dermatológico. Realizaram-se ensaios de determinação de β-glucanases, ensaio de microdiluição, Challenge Test para avaliar a eficácia de ação conservante, análise de estabilidade e teste de irritabilidade de membrana. O sobrenadante WA92 apresentou atividade de β-glucanases de 3,80 U/mg e inibição frente a todos os microrganismos padrão testados em microdiluição. No Challenge Test, os critérios de eficácia conservante foram cumpridos para bactérias, fungo filamentoso e leveduriforme. Os resultados compreenderam uma formulação gel estável e não irritante utilizando micocinas como conservante em diferentes concentrações, a avaliação de estabilidade por meio de viscosidade, densidade e pH e estimativa da capacidade conservante das micocinas, incluindo comparações com conservantes comumente utilizados foram apresentados neste estudo.
... Isothiazolinone releasers, such as methylisothiazolinone (MIT), methylchloroisothiazolinone (MCI), benzisothiazolinone, octylisothiazolinone and dichlorooctylisothiazolinone are antibacterial preservatives that also cause allergy. MIT has been banned in leave-on products due to the significant risk of sensitization, however its maximum concentration in rinse-off products (if included in a mixture with MCI) cannot exceed 0.0015% (Aerts et al. 2014;Herman A 2019;Qin et al. 2020;Vanneste et al. 2013). ...
... The cosmetics industry has just begun a new trend of substituting natural preservatives for artificial preservatives. Scientists have found plants with antibacterial and antifungal properties and evaluated the efficacy, efficiency, and practicability of employing essential oils and extracts from these plants into cosmetics (Pandey et al. 2016;Herman A 2019;Xiao et al. 2020). Plant derivatives are also employed in the food business, with many of them being designated as ''GRAS'' (Generally Recognized as Safe) (Simoes et al. 2009). ...
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Parabens are commonly used as preservatives and antimicrobial compounds in cosmetic, pharmaceutical and food industries. Structurally they are similar to estrogen hormone and they interfere with nuclear receptors for androgens, estrogens, progesterone, glucocorticosteroids etc. Hence, they are considered as endocrine disrupting chemical (EDC)s. Studies in both human and rodents have established the role of parabens in altering steroidogenesis and activity of enzymes that metabolize endogenous hormones. Parabens disrupt normal function of the hormones and lead to reproductive, developmental and neurological disorders; thyroid related problems, skin allergy and cancers. Scientific articles supporting these assertions have led some countries banning or restricting paraben usage. A number of substitutes, both natural and synthetic chemicals are now in market as alternatives of parabens. This review article aims to provide adverse effects of paraben as well as potent paraben alternatives. The major alternatives include formaldehyde, triclosan and phenol, but those chemicals also have toxicity and side effects which are difficult to ignore. Moreover, the natural compounds have low shelf life and less potency. Therefore, more research is needed to establish the alternatives of parabens.
... However, when using these substances, restrictions in the choice of the pH value, the used concentration, the manufacturing process and the spectrum of activity have to be considered. For example, 2-phenylethanol is effective against gram-negative bacteria and mold, but only to a limited extent against gram-positive bacteria and yeasts, while glyceryl caprate is very effective against gram-positive bacteria, but not against mold [1]. The increasing restrictions of synthetic preservatives in the cosmetics sector and the trend towards natural cosmetics place high demands on the hygienic production and filling of the products. ...
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Cleaning of plants as well as hygienic filling are essential processes for ensuring product safety. However, many cleaning processes have been determined empirically and offer enormous potential for saving resources. The use of specific sensors enables a control of the cleaning success and in this way a specific optimization of the processes with regard to the duration, frequency and use of cleaning media. A microbiological validation of sterilization and hygienic filling systems also serves as proof of process efficiency and as a basis for further optimization steps. For this purpose, microbiological challenge tests are carried out using specific test organisms. Resistance-tested bio-indicators are a prerequisite for proving the real efficiency of sterilization processes.
... [4][5][6] Based on a variety of research, the European Commission set a maximum of 0.4 percent of paraben in cosmetic products. 7 Although most other countries still permit the use of parabens business has started to respond to the negative public perception of parabens by labeling their products as "paraben-free". 8 Additionally, it has been reported that some bacterial strains are resistant to conventional. ...
... In the bio-industry, preservatives are added to decrease the bacteria purity during manufacturing, packaging, and storage [21]. However, preservatives such as formaldehyde, iodopropynyl butylcarbamate, and triclosan cause allergies and contact dermatitis in users, even when used in small amounts; therefore, their use is being reduced gradually [22][23][24]. One way to minimize this issue is to use natural substances with antibacterial effects in bioproducts [25][26][27]. ...
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Bioactive compounds are widely used in the bio-industry because of their antioxidant and antibacterial activities. Because of excessive oxidative stress, which causes various diseases in humans, and because preservatives used in bioproducts cause allergies and contact dermatitis, it is important to use natural bioactive compounds in bioproducts to minimize oxidative stress. α-bisabolol (ABS) is a natural compound with both antioxidant and antibacterial properties. However, its water-insolubility makes its utilization in bioproducts difficult. In this study, ABS-loaded polyglyceryl-4 caprate nanoparticles (ABS@NPs) with improved aqueous stability and ABS loading were fabricated using an encapsulation method. The long-term stability of the ABS@NPs was analyzed with dynamic light scattering and methylene blue-staining to determine the optimized ABS concentration in ABS@NPs (10 wt%). The ABS@NPs exhibited excellent antioxidant activity, according to the 2,2-diphenyl-1-picrylhydrazyl assay and in vitro reactive oxygen species generation in NIH-3T3 fibroblast cells, and an outstanding antibacterial effect, as determined using the Staphylococcus aureus colony-counting method. Furthermore, we evaluated the biocompatibility of the ABS@NPs in vitro. This study suggests that ABS@NPs with improved antioxidant and antibacterial properties can be used to treat diseases related to various oxidative stresses and can be applied in many fields, such as pharmaceuticals, cosmetics, and foods.
... Preservatives are added to cosmetic products to prevent the growth of bacteria and fungi during shelf life and to ensure that consumers are protected from the harmful effects of microorganisms. Insufficient use of preservatives can lead to deterioration of the product; on the other hand, excessive use of preservatives can increase the risk of adverse reactions (Halla et al., 2018;Herman, 2019). ...
... Phenonip is a natural preservative used to prevent from microbial spoilage and increase the shelf-life of topical formulations. Besides, plant oils are categorized as synthetic preservatives, wherein their antimicrobial action are based on the inhibition of proteins and polysaccharides synthesis in bacterial cells and denaturation of membrane proteins, leading to outer membrane disruption (Herman, 2018). It has been shown that Moringa oleifera oil has potent antimicrobial activity against different strains of bacteria and fungus (Amina et al., 2019). ...
Psoriasis is a widespread autoimmune inflammatory dermatological disease treated with oral cyclosporine to reduce the uneasiness of psoriasis. However, systemic therapy of cyclosporine is associated with high risk of side effect that limit the usage in psoriasis treatment. Topical delivery of cyclosporine is believed could overcome cyclosporine related toxicity issues. In this study, a new carrier for topical cyclosporine was developed, which cooperated with Moringa oleifera oil (MOO) that has been reported could enhance the moisture-retaining of the skin. Both high-shear homogenizer and overhead stirrer homogenizer were utilized in formulating a cyclosporine-loaded emulsion carrier. Two emulsions were prepared at different proportions of MOO, water and surfactant (Tween80:Span80) based on the constructed ternary phase diagram. Samples with different formulation (E1 and E2) were subjected to several tests including the stability, rheological, colony and in vitro release analysis. E1 and E2 possessed good stability against phase separation for 1 month at different storage temperatures (4, 25 and 40ºC), having pH values within the range of 4 to 5 as well as showing no mould and microbial growth after been incubated on nutrient agar plate at controlled conditions. Optimized formulations were found to be non-Newtonian and followed the pseudoplastic flow behaviour. Nonetheless, E2 exhibited highest permeation of cyclosporine (80.23%) through cellulose acetate membrane via Franz diffusion cell, which correspond to controlled release and best fitted to first order kinetic behaviour (R2=0.9819). This preliminary study suggested that the formulated emulsion has a promising potential as topical medicament for psoriasis.
... Les agents chélateurs, tels que l'EDTA (acide éthylène diamine tétra acétique) ou le GLDA (diacétate de glutamate de tétrasodium) ont la capacité d'augmenter la perméabilité membranaire des bactéries, les rendant plus sensibles aux agents antimicrobiens(Siegert 2014). L'éthylhexylglycérine, généralement utilisé pour ses propriétés tensioactives, émollientes, humectantes et solubilisantes, peut également, à une certaine concentration, favoriser l'activité antimicrobienne de conservateurs tels que le caprylyl glycol, le phénoxyéthanol et le 1,2-pentanediol(Langsrud et al. 2016;Herman 2019). En effet, en raison de sa structure semblable aux tensio-actifs, l'éthylhexylglycérine est capable de déstabiliser la membrane des microorganismes, permettant ainsi au conservateur de pénétrer plus efficacement (Herman 2019).L'efficacité des agents antimicrobiens dans une matrice émulsionnée peut également dépendre de la structure même de l'émulsion. ...
La plupart des produits cosmétiques sont sensibles à la prolifération microbienne, notamment du fait de leur composition riche en eau, de leur conservation à température ambiante et de leur utilisation en plusieurs fois. La gamme de conservateurs utilisables se réduisant, notamment à cause du durcissement de la réglementation, il devient indispensable de déterminer avec précision la capacité de conservation des formules cosmétiques pour prévoir leur durée de vie. Ainsi, l’objectif de cette thèse est de mieux comprendre, de prévoir et d’optimiser le fonctionnement des systèmes conservateurs au sein des matrices cosmétiques. Il s’agira tout d’abord de comprendre le rôle de la matrice (composition et structure) sur la répartition spatiale des microorganismes dans les formules cosmétiques, puis de mettre en place une méthode permettant d’évaluer et de prédire l’action des conservateurs au sein de ces matrices. Le Challenge-test est aujourd’hui encore la méthode de référence pour l’évaluation de la protection antimicrobienne d’un produit cosmétique mais il présente cependant un certain nombre de limites, notamment du fait de la lourdeur des expérimentations et du délai d’obtention des résultats. Nous avons tout d’abord cherché à identifier les déterminants de la distribution spatiale de Staphylococcus aureus, artificiellement inoculés dans des formules cosmétiques, grâce à une méthode associant la microscopie confocale à balayage laser (MCBL) et l’analyse d’images. Nous avons pu montrer que plus la viscosité des formules et/ou l’hydrophobicité des bactéries augmentent, plus la distribution spatiale des bactéries est hétérogène. De plus, nous avons mis en évidence qu’une distribution spatiale hétérogène pouvait induire une variabilité des résultats de dénombrement lors des Challenge-tests. Une méthode rapide a ensuite été développée pour évaluer et prédire l’action des conservateurs dans les formules cosmétiques. Cette méthode est basée sur l’acquisition de données d’inactivation bactérienne obtenues sur des temps courts par MCBL et sur la mise en place de modèles mathématiques d’inactivation. Elle a permis de prédire le nombre de réductions logarithmiques des populations bactériennes sur des temps longs, de même ordre de grandeur que les temps définis dans les challenge-tests. Cet outil devrait ainsi permettre aux industries cosmétiques de gagner du temps dans l’optimisation de la protection antimicrobienne des formules cosmétiques.
... The minimum inhibitory concentration of MIN3 melanin against Staphylococcus aureus was found to be 60μg/mL [ Table 4]. Anti-microbial ingredients can act as preservative booster in cosmetic properties [33]. Effectiveness of MIN3 melanin against pathogenic microbes indicates it could provide an additional preservative potential apart from other efficient cosmetic properties. ...
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Melanins are phenolic polymers synthesized by most of the living organisms. This pigment is mainly attributed to provide photoprotection to the organism while it was found that pigment have immense bioactivities which could be utilized in day-today life ranging from sun screens lotions to solar cells. This pigment produced mainly via DOPA or homogentisate in bacteria. Melanin production is usually triggered by stress condition in bacteria. Marine bacteria have been reported as good melanin producers. In this study marine bacteria capable of melanin production were isolated from sea water of Kutch region, Gujarat using tyrosine basal media. The bacteria were identified using microscopic, biochemical and molecular techniques. Melanin produced by the bacteria is extracted and purified and further characterized using physicochemical techniques. Cosmetic properties of melanin like photoprotection, antioxidant and antimicrobial properties are evaluated.
... It has been determined that molecules such as imidazolimidyl urea, diazolidinyl urea, formaldehyde, paraformaldehyde, benzalkonium chloride, parabens, methylchloroisothiazolinone, methylisothiazolinone, methyl dibromo glutaronitrile, and phenoxyethanol, which are used as preservatives in cosmetic products, may cause allergic reactions in humans and cause side effects related to different tissues and organs [33]. Therefore, in order to reduce the concentrations of antimicrobial synthetic molecules used in cosmetic products, natural preservative boosters of plant origin and also have antimicrobial properties and their mixtures with low doses of synthetic antimicrobial molecules have come to the fore [34]. As a result of many studies conducted in recent years, it has been shown that ethanol extracts, methanol extracts of aqueous extracts obtained from some algae species, and some algal compounds including sesquiterpenes, phenolic ingredients, laurenterols, bromophenols, fatty acids, and sulfated polysaccharides also have antimicrobial activity, and it is thought that these natural compounds can be used for preservative purposes in cosmetic products [35]. ...
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Sargassum vulgare was sampled by free dives in Iskenderun Bay, Hatay, Turkey, in September 2018. Sargassum vulgare is a material with high economic value because it has compounds that can be used in medical applications such as alginic acid and at the same time it contains carbohydrates and vitamins. Alginates were extracted with a sequential extraction protocol from Sargassum vulgare. Structural characterization of alginate obtained from Sargassum vulgare was determined by FT-IR spectrum, phase structure by XRD diffractometer, and surface morphology by SEM image. Within the scope of the study, alginate obtained from Sargassum vulgare and herbal preservative 705 used in the field of cosmetics were compared. After pretreatment of Sargassum vulgare with ethanol, alginate extraction was performed. Microorganisms of Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, Escherichia coli, Aspergillus brasiliensis were used to examine the antimicrobial activity of the obtained alginate and showed that the contamination risk was tolerable for all microorganisms examined on the seventh day of incubation. Alginate obtained from Sargassum vulgare was found to be more effective than herbal preservative 705 at 0 hours. Pseudomonas aeruginosa, Staphylococcus aureus are microorganisms with the highest effect in the 0 hour. Since alginate obtained from Sargassum vulgare is more effective on microorganisms in a shorter time than herbal preservative 705, it is predicted that it can be a product that can be used in the field of cosmetics.
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Infectious diseases caused by bacteria, viruses or fungi are among the leading causes of death worldwide. The emergence of drug-resistance mechanisms, especially among bacteria, threatens the efficacy of all current antimicrobial agents, some of them already ineffective. As a result, there is an urgent need for new antimicrobial drugs. Host defense antimicrobial peptides (HDPs) are natural occurring and well-conserved peptides of innate immunity, broadly active against Gram-negative and Gram-positive bacteria, viruses and fungi. They also are able to exert immunomodulatory and adjuvant functions by acting as chemotactic for immune cells, and inducing cytokines and chemokines secretion. Moreover, they show low propensity to elicit microbial adaptation, probably because of their non-specific mechanism of action, and are able to neutralize exotoxins and endotoxins. HDPs have the potential to be a great source of novel antimicrobial agents. The goal of this review is to provide an overview of the advances made in the development of human defensins as well as the cathelicidin LL-37 and their derivatives as antimicrobial agents against bacteria, viruses and fungi for clinical use.
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ABSTRACT Objective: Oral care cosmetics are essential for all populations and are systematically used to treat oral problems. The chemicals free natural cosmetics are the choice of many people. Thus, this study was aimed to formulate and to assess the natural mouthwash (MW) solution from Lactobacillus fermented Thai medicinal plants juice. Methods: The selected (betel, green tea, clove, black galingale, mangosteen, and noni) plant juices were subjected to Lactobacillus plantarum mediated fermentation. The fermented plant juices (FPJ) were formulated into MW solution with different concentrations of peppermint oil. MW formulations were assessed for physical appearance, stability, and anti-microbial activities. Results: About 2% of peppermint oil in FPJ was found as organoleptically optimum. The pH and refractive indexes of the MWs were not affected during storage and stability assessments. All the FPJ-MWs formulations showed antimicrobial activity against Group A Staphylococcus, and other oral pathogens - Escherichia coli, Streptococcus aureus, and Pseudomonas aeruginosa. Moreover, black galingale, mangosteen, and noni based MW formulas also exhibited anti-candida activity. The MW made from fermented black galingale (Kaempferia parviflora) juice was the most potent antimicrobial formulation with excellent physical stability. Conclusion: The study concluded that fermented plant-herbal juices can be used as natural MW recipe with 2% of peppermint oil to improve the flavor and aroma. The formulations were stable, free of microbial contamination, and also exhibited antimicrobial activity. Further extended stability study and clinical trials are necessary to develop a commercial FPJ-based natural MW recipe.
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Preservatives are added to cosmetics to protect the consumers from infections and prevent product spoilage. The concentration of preservatives should be kept as low as possible and this can be achieved by adding potentiating agents. The aim of the study was to investigate the mechanisms behind potentiation of the bactericidal effect of a commonly used preservative, 2-phenoxyethanol (PE), by the potentiating agent ethylhexylglycerin (EHG). Sub-lethal concentrations of EHG (0.075%) and PE (0.675%) in combination led to rapid killing of E. coli (> 5 log reduction of cfu after 30 min), leakage of cellular constituents, disruption of the energy metabolism, morphological deformities of cells and condensation of DNA. Used alone, EHG disrupted the membrane integrity even at low concentrations. In conclusion, sub-lethal concentrations of EHG potentiate the effect of PE through damage of the cell membrane integrity. Thus, adding EHG to PE in a 1:9 ratio has a similar effect on membrane damage and bacterial viability as doubling the concentration of PE. This study provides insight about the mechanism of action of a strong potentiating agent, EHG, which is commonly used in cosmetics together with PE.
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Opinion statement Preservatives serve the necessary purpose of preventing microbial contamination and maintaining cosmetic product integrity and safety; however, there are limitations to their use. Preservatives, including formaldehyde (FA) and formaldehyde releasers (FRPs), isothiazolinones, iodopropynyl butylcarbamate (IPBC), methyldibromoglutaronitrile (MDBGN), parabens, thimerosal, and triclosan, are a leading cause of allergic and irritant contact dermatitis, and there is increasing evidence that some may even cause toxic effects including endocrinological effects. One approach to minimizing these effects is the use of self-preserving or preservative-free cosmetic formulations. This article will outline these preservatives, their role in cosmetics, scientific evidence for allergy and toxic effects, and potential alternatives.
In the last few years, the rapid and continuing emergence of antibiotic resistance for microbial pathogens has questioned the future utilisation of antibiotics. Thus, the discovery of new antimicrobials is highly desired to fight microorganisms with multi-drug resistant capability. Here, we have used an inorganic UV filter as a model system to investigate the behaviour of a new preservative, based on Ag-Zn cations, to replace parabens in sunscreens. The new glass preservative is incorporated into the UV filter composite by using an easy and eco-friendly method based on a dry nanodispersion. The Challenge Test clearly demonstrates a robust toxicity towards microorganisms both the resistant bacteria and the fungi. This stimulant behavior can be explained by coupling between the antimicrobial activity of the Ag+ and the antifungal activity of Zn+2. Importantly, leaching assays show that the controlled released of these cations over time results in a long-lasting antimicrobial property, pointing out that this material is a promising paraben-free candidate.
Lately, the cosmetic and personal care market has been more and more driven toward natural ingredients by the rising consumers' awareness about personal health and safety and their will for safer cosmetics free of harmful chemicals. Preservatives are no exception to the rule: evidence or suspicion of the toxicity of certain synthetic preservatives that have been around for decades pushed the cosmetic industry forward to seek for natural alternatives, as the selection of natural preservatives already available is quite limited. Sourcing active metabolites and developing new natural ingredients are long-term procedures that are thoroughly described in the present paper, via the example of the design of a natural preservative based on the Santolina chamaecyparissus extract, and of the assessments of its preservative effectiveness.
Model emulsions were developed with or without commercial titanium dioxide nanoparticles (NP) carrying various surface treatments in order to get close physicochemical properties whatever the NP surface polarity (hydrophilic and hydrophobic). Rheology and texturometry highlighted that the macroscopic properties of the three formulated emulsions were similar. However, characterizations by optical microscopy, static light scattering and zetametry showed that their microstructures reflected the diversity of the incorporated NP surface properties. In order to use these model emulsions as tools for biological evaluations of the NP in use, they had to show the lowest initial microbiological charge and, specifically for the NP-free emulsion, the lowest bactericidal effect. Hence, formulae were developed preservative-free and a thermal sterilization step was conducted. Efficiency of the sterilization and its impact on the emulsion integrity were monitored. Results highlighted the effect of the NP surface properties: only the control emulsion and the emulsion containing hydrophilic NP fulfilled both requirements. To ensure the usability of these model emulsions as tools to evaluate the ‘NP effect’ on representative bacteria of the skin microflora (S. aureus and P. fluorescens), impact on the bacterial growth was measured on voluntary inoculated formulae.
Objective: This study describes a new alternative combination preservative containing caprylyl glycol, phenethyl alcohol, and glyceryl caprylate and investigates the effects of the particle size of the emulsion droplet on the antimicrobial activity of the said blend in the formulation. Methods: The antimicrobial activity of the ingredients and the blend were determined via MIC, MBC, MFC, and fractional inhibitory concentration (FIC) determination using the broth microdilution method. The blend inhibited the microorganism contamination of the oil-in-water emulsion, and its performance was affected by the particle size of the emulsion droplet, as shown by the in vitro microbial challenge test. Results: Results show that the MIC/MBC/MFC values of the blend were lower than those of any of the ingredients used alone. Any two of the ingredients presented no antagonistic activities against all the tested microorganisms, and synergism or additive effects were also observed. The challenge test also showed that the action of the blend against bacteria and yeast was only 0.3% and 0.2%, respectively, and mold was completely inhibited at 1.4%, meeting the requirements of the PCPC and European Pharmacopoeia. The results showed that antimicrobial activity was gradually enhanced when the particle size of the emulsion droplets increased significantly in the range of 100-900 nm. A positive correlation was found between antimicrobial activity and particle size. Conclusion: The synergistic performance of caprylyl glycol, phenethyl alcohol, and glyceryl caprylate and the antimicrobial activity of their blend suggest that their combination is effective and exhibits broad-spectrum antimicrobial activity. Furthermore, the results show a positive correlation between the antimicrobial activity of the preservative and the particle size of the emulsion droplets in the range of 100-900 nm, when the same concentration of the blend is used in the same formulation. The particle size of the emulsion droplets is demonstrated to be a newly-discovered factor that influences the preservation of cosmetic products. This article is protected by copyright. All rights reserved.
Background: Ethylhexylglycerin is a relatively new cosmetic ingredient that is used for its surfactant, emollient, skin-conditioning and antimicrobial properties. Since 2002, it has been occasionally reported as a contact allergen. Objectives: To report on 13 patients who presented with allergic contact dermatitis caused by ethylhexylglycerin, evaluated at two Belgian university patch test clinics during the period 1990-2015. Patients and methods: The patients were patch tested with the European baseline series, a cosmetic series, and - if indicated - additional series. Both the cosmetic products used and their single ingredients were patch tested. Results: All but one of the ethylhexylglycerin-allergic patients were female, with a median age of 43 years (range: 29-81 years), most often suffering from dermatitis on the face, and sometimes on the hands and/or axillae. As the culprit products, leave-on cosmetics were identified, including a high number of proclaimed 'hypo-allergenic' and 'preservative-free' facial creams, sun protection creams, and deodorants. Conclusions: Ethylhexylglycerin is a rare, but highly relevant, cosmetic sensitizer, even in those products advertised to be safe for consumers. Targeted patch testing with ethylhexylglycerin 5% pet. is very useful, and routine patch testing in a cosmetic series may be considered. Higher test concentrations might be indicated in selected cases.