The Applications and challenges of Probiotics/ Postbiotics in Cosmetic and personal care products

According to the U.S. Food and Drug Administration (FDA), a cosmetic is defined as “a product (excluding pure soap) intended to be applied to the human body for cleansing, beautifying, promoting attractiveness, or altering the appearance.” This definition applies to products for skin, hair, and oral care. It is important to note that this description does not include any health claims. Using beneficial microbes to manipulate the microbiome in a given niche in favor of health has grown substantially in the field of products. Nowadays, the market for postbiotics products has maintained robust growth momentum worldwide. Postbiotics, defined as extracts of non-viable probiotics and comprising cell membrane components such as surface proteins, lipopolysaccharides, teichoic acids, etc., can be single metabolites or complex mixtures [1].

The market for probiotics/postbiotics in cosmetic applications is projected to snowball in the next ten years. This article will explore current research on probiotics/postbiotics for potential cosmetic and personal care applications and how “probiotic cosmetics” are currently being marketed.

Cosmetics for skin

The increase in products termed probiotic on the market does not necessarily equate with a reason to celebrate the successful translation of science to commerce and consumers. Too many products fail to comply with the characteristics of probiotics. Many false claims and rampant misuse of the term have resulted in mainstream consumer channels providing incorrect information to consumers. Probiotics are not inside us, not in fermented food, and not necessarily better if there are more species or a higher viable count. Formulations are being concocted not based on research evidence but on marketing and what might appeal to consumers. For example, products are being composed supposedly to improve oral health using strains not documented to compete with urogenital pathogens, improve immunity or do anything that can restore homeostasis to that region of the body. In other words, there are no data to support their selection. Yet, the internet, the use of words to reach the first page of search engines, and the use of pseudo-experts for promotion provide a means for these products to be highly rated and appear to be the best clinically documented for preventing or curing pathogen infections in the skin or vagina. The net result is misleading and confusing to consumers, making personal care professionals leery of the whole field of probiotics. To counter this, we need to re-state essential facts. For a product to be considered probiotic, it must comply with three core characteristics: 1. The strain(s) must be characterized, including genetically and phenotypically, and a rationale given based on documented experiments published in peer-reviewed papers for their inclusion in the intended use. 2. The product must contain sufficient efficacy at the time of use that is equivalent to when the product was shown in clinical studies to confer a benefit to the desired target site. 3. The delivery method, dosage, and duration of use should be based on scientific evidence in humans if humans are the intended recipient. It makes it difficult for potential users if the product label does not state strain designations because tracking the research performed on the contents becomes impossible. Dosages are rarely stated on labels, and some products only contain filtered extracts, ferments, or lysed bacteria, meaning that no live microorganisms are present. Thus, the product is not probiotic, and the term should not have been used.

The cosmetic industry has quickly entered this space by focusing its efforts on skincare. There are several areas of opportunity and great value in this concept. To date, hundreds of products are already being commercialized with a claim to contain probiotic or postbiotics cosmetics in China. Figure 1 shows a word cloud with the top 30 terms used in their statements. Most are for skin care, while some are for deodorants and hair care. The most common claims are geared towards “balancing” the skin microbiome, improving the skin barrier, and enhancing the skin’s overall appearance. The type of probiotic products targeted for skincare usually involves cream, serum, mask, gel, exfoliant, cleanser, foundation, soap bar, balm, or primer deodorant. And the ingredients of these products mainly include Lactococcus ferment lysate, Lactobacillus ferment, Bifida ferment lysate, Streptococcus thermophiles ferment, Bacillus coagulans, Saccharomyces ferment filterate, Lactococcus ferment extract, Leuconostoc ferment filtrate, etc.

These claims by themselves require critiquing. There is no single healthy skin microbiome, so what would it take to “balance” the one that a given individual possesses? Furthermore, the skin has many layers, with microbes detected in the dermis, adipose, follicle, and epidermis [2]. A product claiming to “balance” the microbiome should have studies indicating in many subjects, preferably thousands, how a given probiotic product changes the various layers of microbiota in such a way as to restore and maintain it to what is deemed healthy for each individual. Since it seems highly unlikely that such studies have been performed for most products, claims of balancing the skin microbiome should not be made. It is vital because consumers like the sound of products that do that, especially since terms like “microbiome” and “balance” are widely used.

Enhancement of the skin’s overall appearance can be subjective for consumers, but it also has some scientific principles. Factors such as contrast reduction, visible aging marks or spots, skin color, melanin, and hemoglobin can be measured [3]. Assessments provide the means to give tangible results that can then offer substance to claims of improvements. The ability of specific probiotic strains to improve epithelial and epidermal barrier function has been reported. The latter is so critical in the function of the skin and a well-used target for making claims that appeal to consumers. If strains being used as cosmetics do indeed improve barrier function, experiments can be performed to verify this. Indeed, researchers from a well-renowned cosmetic company have shown that a lysate from the probiotic Bifidobacterium longum Reuter strain could decrease vasodilation, edema, mast cell degranulation, and TNF-alpha release, and using trans-epidermal water loss to assess barrier function, showed improvement with application of the lysate containing product [4]. Some products state that they include a filtrate of either ferments or lysates. In the case of filtrates, bacterial cells (alive or not) are removed along with potentially some other large-weight molecules (e.g., peptides). Some bioactive compounds and bacterial cell compnents might be removed during these processes. Therefore, filtrates are excluded from the definition of postbiotics and cannot be deemed probiotics.

Lysates are cells whose outer membrane has been broken down due to chemical or physical processes [5]. These preparations have been used in medical practice as immunomodulators for fifty years. They can contain bacterial components that up-regulate the immune response of the host cells; they are particularly effective in managing skin issues [6]. Although there is value in using these types of preparations, further studies are still required on a strain-dependent basis before drawing conclusions and making claims. The cell composition, elasticity, and activation of macrophages differ between bacterial strains, even within the same species [7]. In one study, lactobacilli lysates altered their ability to increase the re-epithelialization of keratinocytes [8], again emphasizing the need to check strain properties before making claims. Notably, little has been reported on the chemical composition of the lysates used in cosmetics. This should require cell wall and analysis, including the use of liquid chromatography–tandem mass spectrometry (LC-MS/MS)-based metabolomics [9] or newer methods such as surface-enhanced Raman spectroscopy (SERS) [10]. In doing so, it will soon be highly apparent that metabolite types and quantities differ between strains; therefore, their application to human tissues would also differ. This again illustrates the need to perform tests in humans with whole microbial cells, lysates, or filtrates to show what activity is being promoted by applying any given product, ideally to know which component of the lysate is responsible.