Probiotics, prebiotics and postbiotics in cosmetic products
This article has been translated from Finnish to English by Semantix. You can find the original article at the web adress https://www.kosmetiikka-allergia.fi/tietoa-kosmetiikasta/probiootit-prebiootit-ja-postbiootit-kosmetiikkatuotteissaKirjaudu
Cosmetic skin care products that contain probiotics, prebiotics and/or postbiotics have recently entered the market. Probiotics are living bacteria or products that contain microbes. Prebiotics support the growth of probiotics by providing them nutrients. Prebiotics include, for example, fibrous carbohydrates and polysaccharides. Postbiotics are bioactive compounds produced by probiotic bacteria when they use prebiotics as their nutrients. Bacterial components, bacterial metabolites or fermented ingredients are currently used in probiotic skin care products. Adding probiotics into cosmetic products is expected to balance the living microbiome on the skin and provide a better-functioning and healthier-looking skin. Cosmetic products containing probiotics are currently marketed especially for people who have a sensitive skin. The EU Regulation (EC) No 1223/2009 on Cosmetic Products sets the maximum limits for microbes allowed in different products. Cosmetics do not have to be sterile, but they must not contain pathogenic or virulent microbes that may cause diseases.
Microbiology terms
Microbe or microorganism
Collective name for tiny organisms that are found in various living organisms. Microbes include bacteria, viruses, yeasts, protozoa, and many fungi, such as moulds. These organisms are not visible to the naked eye. A collection of microbes is called microbiota.
Normal flora or normal microbiota
Humans and animals have a living normal microbiota, for example, on the skin, mucous membranes or in the intestine. Normal flora is usually harmless and it protects various organs and body structures by preventing the growth of harmful microbes.
Microbiome
The aggregate of normal microbiota and their genomes, i.e. genetic information, is called microbiome. The size of microbiome is huge: its total number of genes exceeds that of all human cells by several hundred times. Microbiome can be viewed as an external genome of the human, and one of its purposes is to connect the environmental factors to the body’s immune system.
Probiotics
Are benign and ‘friendly’ bacteria that live in the gut and support the health by converting the dietary fibres into compounds that promote a good health. Probiotics are viable microorganisms in active or dormant state, and they are added to products, for example, to enhance the effect of a cosmetic product.
Prebiotics
Prebiotics are not living microorganisms. They are a group of nutrients, mainly fibres, that provide nutrition to the good bacteria. Prebiotics are used to nourish the microbiota on the skin area where the product is applied. The purpose is to enhance the effect of the cosmetic product.
Postbiotics
Postbiotics are bioactive compounds that the probiotic bacteria produce (as a result of a fermentation process) when they use the prebiotics (fibre) as their nutrition. There are various kinds of postbiotics, and they provide similar kinds of health benefits as probiotics.
The importance of the body microbiome to our health
Child’s microbiome begins to develop at birth, and, at a few years of age, it starts to resemble the normal microbiota of an adult. Each person has a unique microbiome, and it changes during their lifetime, but the changes are clearly smaller than between different individuals. Today, the research has shown that the microbiome, especially the gut microbiome, has a huge impact on our health and well-being. There is scientific evidence on the health issues associated with the imbalance of the normal gut microbiome. The Western way of life, diet and living conditions may have reduced the diversity and composition of our microbiome. The studies have shown that diverse microbiota are able to better adapt to the environmental changes and can therefore maintain and promote our health. It is believed that the balance between the different microbial species that form our microbiome is essential for our health. Different microbes interact with their host, i.e. the human cells and immune system, to the benefit of both the microbes and the host or only one of them.
Skin microbiome
The skin is one of the body’s largest organs, and it serves as an interface between the body and environment. For each square centimetre of skin, there are approximately a billion microbes that include bacteria, fungi and viruses. The composition of the skin microbiome varies between individuals and populations, and it is influenced by several factors, such as geographical location, environmental factors, state of health and behaviour.
The microbiota of healthy skin is relatively permanent and unique from person to person. Different skin areas provide different living conditions for microbes, and each area is inhabited by microbiota that thrives in that specific area. The composition of the skin microbiome is affected by the temperature, humidity, nutrients available for microbes, pH of the skin and other physical and chemical factors. For example, the level of personal hygiene affects the skin microbiome. Soaps and other cleansing products, various skin care and make-up products change the conditions of the skin, which may affect the microbial species living on it.
Facts about how cosmetic products influence the skin microbe
Since skin care products are used daily, they affect and are intended to affect the microbiota of the skin. Antibacterial hygiene products or products for impure skin are intended to destroy or prevent the growth of harmful microbes on the skin. Preservatives that destroy bacteria, mold and yeast are added to the cosmetic products to ensure their preservation. Preservatives are added to products that include water to prevent their contamination and growth of virulent or pathogenic microbes in the products. Pathogenic microbes could cause skin reactions and/or infections to the user of the product. The EU Regulation on Cosmetic Products stipulates that the cosmetic products made available on the market must be safe for use. The Regulation does not require the products to be sterile, but they must meet certain microbiological specifications, which are ensured by different tests before making the products available on the market. The legislation also defines what products are considered as cosmetics and what are their intended uses. Cosmetic products are not allowed to include any medical claims. For example, a product cannot claim to cure a disease that is medically diagnosed.
According to various studies on the skin microbiome, it can be assumed that the preservatives, i.e. substances that kill the microbes, used in the cosmetic products could also deplete the skin’s own microorganisms. The research on the effects of preservatives on the skin microbiome is still in its infancy. A recent preliminary study found that the currently widely used mixture of phenoxyethanol and ethylhexylglyceryl (concentration of 1%), which is used as a preservative, had only a minor effect on the number and even the distribution of microbes in the tested area and had no significant effect on the microbiota on the tested area 1 (Holsten, L. & Weber, K. 2021). However, it is only a single study and the size of the sample was small. More reliable studies on the effect of antibacterial agents on the normal flora of the skin are needed.
Use of probiotics, prebiotics and postbiotics in cosmetic products
The name ‘products containing probiotics’ is often collectively used of the cosmetic products that contain probiotics, prebiotics and/or postbiotics. Cosmetic products that contain probiotics are regulated by the EU Regulation on Cosmetic Products. No specific guidelines for the use of these products or a definition for them have yet been established in the EU Regulation on Cosmetic Products. The issue has already been discussed in the EU, but no decisions have been made yet. In Finland, the Finnish Safety and Chemicals Agency (Tukes) gives instructions on the use of probiotics according to the EU Regulation which stipulates the maximum number of microbes for each category of products. If the maximum limit is exceeded, the safety of the product must be demonstrated in the safety report.
For a long time, the cosmetic products have been developed by closely following the results of the nutrition research. Several substances, especially those derived from wild or cultivated plants, that have been found to be beneficial to the health when used as nutrients are now used in cosmetic products. Research data has encouraged some cosmetic enterprises to use bacteria and/or their lysates (broken bacteria) in skin care products. These products are promised to balance the living microbiota on the skin and thus contribute to a healthier-looking skin. Many probiotic cosmetic products use microbes that are the same or similar to those ones that naturally live on our skin.
The cosmetic products that affect on the microbiota on the skin are believed to have two kinds of effects when applied externally. When probiotics are added to the skin, the number of beneficial microbes increases. Prebiotics serve as nutrition for probiotics, gradually increasing the growth of the good bacteria and preventing the growth of the harmful bacteria. Postbiotics are fermented by-products of the probiotic bacteria, and they are particularly believed to enhance the condition of the skin. Several skin care products that contain probiotics, prebiotics and/or postbiotics are currently available on the global market. When these ingredients are added to the products, they support each other’s functions.
Currently, the most used probiotics in cosmetic products are lactic acid bacteria (lactobacilli) and especially their inactivated forms. The most research data exists on the external use of lactic acid bacteria, although further research is needed, for example, about the long-term effects of their use. Gluco-oligosaccharides and inulin, for example, are used as prebiotics. Although postbiotics are considered waste of the probiotic bacteria, they provide the body a variety of health benefits. This happens because many of the health benefits associated with probiotics and prebiotics are actually provided by postbiotics. There are different kinds of postbiotics: short-chain fatty acids, lipopolysaccharides, exopolysaccharides, enzymes, cell wall fragments, bacterial lysates (a mixture of bacterial components), cell-free supernatants (a mixture of bacterial and yeast-produced compounds) and many other microbial metabolites, such as vitamins and amino acids.
Today, the living bacteria are used very little in the cosmetic product development (although it is difficult to evaluate the global situation as the legislation of different continents vary) since their use makes it particularly difficult to preserve the microbiological stability of the products. The EU Regulation on Cosmetic Products also sets the maximum values for the living bacteria in the cosmetic products, as we have seen earlier.
Probiotics, prebiotics and postbiotics in cosmetic products in the future
The insights provided by the scientific research on the microorganisms living on skin and their impact on the human health and well-being have increased the interest of the cosmetics industry in the skin microbiome. A fair number of new cosmetic products that include probiotics, prebiotics and postbiotics have entered the market.
The EU Regulation on Cosmetic Products has not yet provided instructions or specific regulations on the products affecting the skin microbiome. The legislation on food supplements stipulates that the probiotic, i.e. the living microbe, in the supplements that aim to affect the microbiota of the gut and its function must be carefully studied and mapped (i.e. the genome of the microbe must be defined). The dose of the probiotics must also be scientifically documented, and the achieved health benefits must be demonstrated through clinical studies. It is also important that the probiotics are safe to use.
The use of probiotics in cosmetic products is being discussed both in the EU and the USA. The authorities around the world are pondering whether the current regulations are sufficient or not. The global discussions on the topic have been increasing, and it is expected that there will be clarifications to the regulations in the next few years. The safety of the consumers is essential, and it is also important to ensure the product safety throughout its life cycle.
Given the fact that the skin and gut microbiome is known to be important to our health, the effects of different functional ingredients to the skin microbiome should be explored and considered in the development of new cosmetic products. A lot of research is needed on the topic.
Maria Pesonen, Specialist in Dermatology and Allergology, has read and commented on the text.
Ritva Kurimo, M.Sc. (organic chemistry)
Consulting chemist in cosmetics
Reference: 1. Holsten, L. & Weber, K. 2021. Phyla Friendly? Preservatives vs. the Skin Microbiome. Cosmetics & Toiletries. November. Available at: https://www.cosmeticsandtoiletries.com/magazine/49176 (Accessed: 14 December 2021)