This is not my own work. It is taken from the article that is mentioned at the foot of this page. If you are interested in the more technical aspects of preservatives in your skincare, I would urge you to follow the link to the full article. Any italics are mine!
Cosmetics are made up of various ingredients that work together to achieve different effects. The main components of cosmetics include: (1) Base ingredients, which form the foundation of the product and provide its texture and consistency, such as water, surfactants, oils, polymers and emulsifiers; (2) Active ingredients, which are the key ingredients that deliver the desired effect of the cosmetic product. For example, moisturisers often contain ingredients like hyaluronic acid or :glycerine to hydrate the skin, while anti-aging creams may contain retinol or peptides to reduce the appearance of wrinkles (3) Colorants, which are responsible for adding colour to cosmetics. They can be natural pigments derived from plants or minerals, or synthetic dyes.
Cosmetics, especially those with high water content can also provide a favourable environment for the growth of bacteria, fungi, and other microorganisms. Thus, preservatives are needed to help prevent microbial contamination and extend the shelf life of the products. Without preservatives, cosmetics would have a shorter lifespan and could potentially become breeding grounds for harmful bacteria. By adding preservatives, cosmetic manufacturers ensure that their products remain safe for use throughout their intended shelf life. This is particularly important for products that come into direct contact with our skin, such as moisturizers, serums, and makeup. Preservatives help to protect us from potential infections or irritations that may arise from contaminated products.
Here are some preservatives:
The most commonly used phenol preservatives are Phenoxyethanol and Benzyl alcohol. Phenoxyethanol also known as ethylene glycol monophenyl ether, is a widely used ingredient in cosmetics and personal care products. It serves multiple functions in these products, including as a preservative and solvent. In addition to its antimicrobial activity, phenoxyethanol also possesses other beneficial properties in cosmetics. It has a low volatility, meaning that it evaporates slowly, enabling it to act as a stabiliser and increase the shelf life of cosmetic formulations. Phenoxyethanol is also soluble in both water and oil, allowing it to be used in a wide range of cosmetic products, including creams, lotions, and serums.
Benzyl alcohol is a colourless liquid with a mild, pleasant aroma and is commonly used as a solvent as well as a preservative in cosmetics. It is bacteriostatic and moderately active against Gram-positive bacteria, molds, fungi, and yeasts in concentrations of 0.9–2.
Parabens are the alkyl esters of parahydroxybenzoic acid which are commonly used in cosmetic food, cosmetics and pharmaceutical products for their antimicrobial properties. Methylparaben, Ethylparaben, Propylparaben and Butylparaben are the most commonly used parabens. The antimicrobial effect of the parabens has been shown to increase with increasing chain length of the alcohol component. Parabens are proved to effective especially against fungi. In addition, more than one paraben is normally used in a single product. However, regulatory bodies such as the European Commission and certain state regulations in the U.S. have implemented specific bans on the use of propylparaben and butylparaben in cosmetics, particularly in products designed for children. These restrictions stem from studies indicating that some parabens may accumulate in the body over time and disrupt endocrine function.
Organic acids are naturally occurring compounds and are normally added to foods or cosmetics as preservatives. The commonly used organic acids in cosmetics include Benzoic acid, Sorbic acid, Dehydroacetic acid, Caprylhydroxamic acid and their derived salts.
Alkanediols are a group of organic compounds that have multiple hydroxyl groups attached to their carbon atoms. They are commonly used in various industries, including food, pharmaceuticals, and personal care products. Alkanediols have gained attention due to their unique properties, such as their ability to provide solubilisation and moisturisation. The most commonly used alkanediols in cosmetics are 1,2-alkanediols, including Pentylene Glycol, 1,2-Hexanediol, Caprylyl Glycol and Ethylhexylglycerin. The primary mechanism through which alkanediols exert antimicrobial effects is membrane disruption.45 Alkanediols are amphiphilic thus can integrate into the cell membranes of micro-organisms.
Cationic surfactants, widely recognised for their antimicrobial properties, are increasingly utilized as preservatives in cosmetic formulations. These surfactants exhibit a positive charge, which allows them to interact effectively with negatively charged bacterial and fungal cell membranes. By disrupting the integrity of these membranes, cationic surfactants can inhibit the growth of microorganisms, thereby extending the shelf life of cosmetic products. Quaternary Ammonium Compounds (Quats) include a variety of ingredients, such as Benzalkonium Chloride, Cetrimonium Bromide and Benzylkonium Chloride which possess both conditioning and antimicrobial properties, making them suitable for use in hair conditioners and creams. Maximum concentration of 0.1 % is given for 'Benzalkonium chloride, bromide and saccharinate' both in EU and Chinese regulations.
Natural preservatives derived from plant sources are becoming increasingly popular in the cosmetics industry due to their perceived safety and eco-friendliness. These natural preservatives, such as essential oils, antimicrobial peptides (AMPs) and plant extracts offer antimicrobial properties that help prevent the growth of microorganisms in cosmetic products.
Essential oils are mainly a mixture of complex volatile small molecule compounds. They are concentrated hydrophobic liquids containing volatile aroma compounds from plants. They are typically extracted through methods like steam distillation, cold pressing, or solvent extraction. Each essential oil has a unique composition depending on the plant species, extraction method, and environmental factors. They have a wide range of effects, including anti-acne, anti-aging, skin brightening, photoprotection, anti-microbial, anti-inflammatory and antioxidant.
Essential oils contain volatile compounds that possess antimicrobial properties. For instance, Essentials oils from Lavandulla Officinallis, Melaleuca Alternifolia, Cinnamomum Zeylanicum showed higher inhibitory activity against tested microorganism strain than methylparaben. Essential oil compounds have garnered attention for their potential as natural preservatives in cosmetic products due to their antimicrobial and antioxidant properties. Linalool, commonly found in lavender oil, linalool not only imparts a pleasant fragrance but also exhibits antimicrobial activity. It can be added to cosmetic products to help protect against microbial contamination while providing a soothing scent. Tea tree oil is often used in skincare products to prevent infections and acne. The active compound, terpinen-4-ol, has demonstrated effectiveness against a wide range of microbes.
Plant extracts are used as natural preservatives often contain bioactive compounds, such as flavonoids and phenolic compounds, which have antimicrobial properties. These compounds can inhibit the growth of bacteria, fungi, and other microorganisms by disrupting their cellular processes. They may interfere with microbial enzyme activity, disrupt cell membrane integrity, or interfere with DNA replication, leading to microbial cell death. Common plant-derived natural preservatives in cosmetics are tea polyphenols, grape seed extract and lemongrass extract.
One mechanism by which plant extracts exhibit antibacterial activity is by increasing the permeability of bacterial cell membranes. Plant polysaccharides, for example, can disrupt the integrity of the cell membrane, leading to the leakage of cellular contents and eventually bacterial cell death. It is important to note that research on the antibacterial mechanisms of plant extracts is still ongoing, and multiple factors contribute to their efficacy. The composition and concentration of active compounds, as well as the specific bacteria targeted, can influence the antibacterial activity.
NOT MY OWN WORK. Taken from:
Mechanism of action of preservatives in cosmetics Journal of Dermatologic Science and Cosmetic Technology
Volume 1, Issue 4, December 2024, 100054 Zhenyu Tang, Qiaoyan Du Henning Chemical (Shanghai) Co., Ltd., China
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