Abstract: Probiotics, defined as “live microorganisms that, when administered in adequate amounts,confer a health benefit on the host,” are becoming increasingly popular and marketable. However, toomany of the products currently labelled as probiotics fail to comply with the defining characteristics.In recent years, the cosmetic industry has increased the number of products classified as probiotics.While there are several potential applications for probiotics in personal care products, specificallyfor oral, skin, and intimate care, proper regulation of the labelling and marketing standards isstill required to guarantee that consumers are indeed purchasing a probiotic product. This reviewexplores the current market, regulatory aspects, and potential applications of probiotics in thepersonal care industry.
Keywords: probiotics; cosmetics; lysates; skin; microbiome; vaginal health
1. Introduction
According to the US 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” [1]. This definitionapplies to products for skin, hair, and oral care. It is important to note that this descriptiondoes not include any health claims.
The increased interest in microbes colonizing the human body, not simply thoseinfecting it, has led to many studies attempting to manipulate the microbiome in a givenniche, in favour of health. The use of beneficial microbes for this purpose has seen the fieldof probiotics grow substantially. Defined as “live microorganisms that, when administeredin adequate amounts, confer a health benefit on the host,” probiotic applications rangewidely in type, scope, and application [2]. This includes cosmetic applications, where themarket for probiotics is projected to grow at a 12% rate in the next ten years, with NorthAmerica the driver [3].
This article will explore current research on probiotics for potential cosmetic andpersonal care applications and how “probiotic cosmetics” are currently being marketed.
2. Cosmetics for Skin
The increase in products termed probiotic on the market does not necessarily equatewith a reason to celebrate the successful translation of science to commerce and consumers.Too many products fail to comply with the characteristics required to be called probiotic.Many false claims and rampant misuse of the term has resulted in mainstream consumerchannels providing incorrect information to consumers. Probiotics are not inside us, not infermented food, 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 andwhat might appeal to consumers. For example, products are being composed supposedly
to improve vaginal health using strains not documented to compete with urogenitalpathogens, improve immunity or do anything that can restore homeostasis to that regionof 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 use of pseudo-experts forpromotion provide a means for these products to be highly rated and appear to be the bestclinically documented for preventing or curing bacterial or yeast infections in the vagina.
The net result is misleading and confusing to consumers, as well as making healthcareprofessionals leery of the whole field of probiotics. To counter this, we need to re-stateimportant 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 arationale given based on documented experiments published in peer-reviewed papers,for their inclusion for the intended use. 2. The product must contain sufficient livemicroorganisms at the time of use that are equivalent to when the product was shown inclinical 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 theintended recipient.
It makes it difficult for potential users if the product label does not state strain des-ignations because it becomes impossible to track the research performed on the contents.Dosages are rarely stated on labels, and some products only contain filtered extracts orferments or lysed bacteria, meaning that no live microorganisms are present: thus, theproduct is not probiotic and the term should not have been used.
The cosmetic industry has ventured into this space by focusing its efforts towardsskincare. There are several areas of opportunity and great value in this concept.
A search of the websites of two major retailers of cosmetics in North America revealedthat at least 50 products are already being commercialized with a claim to contain probi-otics [4,5]. Figure 1 shows a word cloud with the top 30 terms used in their statements. Themajority of them are targeted for skincare, although some are for deodorants and hair care.The most common claims are geared towards “balancing” the skin microbiome, improvingthe skin barrier, and enhancing the skin’s overall appearance. Table 1 breaks down thetypes of products included in this analysis, and Table 2 includes the ingredients as listedon their labels; all of them correspond to different types of products targeted for skincare.All products included in this analysis can be used by any gender.
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and what might appeal to consumers. For example, products are being composed suppos-edly to improve vaginal 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 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 bacterial or yeast infections in the vagina.
The net result is misleading and confusing to consumers, as well as making healthcare professionals leery of the whole field of probiotics. To counter this, we need to re-state important facts.
For a product to be considered probiotic, it must comply with three core characteris-tics: 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 for the intended use. 2. The product must contain sufficient live micro-organisms at the time of use that are 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 in-tended recipient.
It makes it difficult for potential users if the product label does not state strain desig-nations because it becomes impossible to track the research performed on the contents. Dosages are rarely stated on labels, and some products only contain filtered extracts or 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 ventured into this space by focusing its efforts towards skincare. There are several areas of opportunity and great value in this concept.
A search of the websites of two major retailers of cosmetics in North America re-vealed that at least 50 products are already being commercialized with a claim to contain probiotics [4,5]. Figure 1 shows a word cloud with the top 30 terms used in their state-ments. The majority of them are targeted for skincare, although some are for deodorants and hair care. The most common claims are geared towards “balancing” the skin micro-biome, improving the skin barrier, and enhancing the skin’s overall appearance. Table 1 breaks down the types of products included in this analysis, and Table 2 includes the in-gredients as listed on their labels; all of them correspond to different types of products targeted for skincare. All products included in this analysis can be used by any gender.
Figure 1. The top 30 words used in the claims of cosmetics marketed as probiotics. Word cloudgenerated using a compilation of the claims of 50 cosmetic products claiming to contain probiotics.Text analysis performed using the rtweet [6] and tm [7] packages in R version 4.0.2.
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Table 1. Cosmetic products currently marketed as probiotics. Percentage corresponding to the differ-ent types of products currently marketed as “probiotic cosmetics.” Data obtained from 50 productsadvertised by major retailers of cosmetics [4,5].
TYPE OF PRODUCT PROPORTION OF PRODUCTS
Deodorant 2%
Primer 2%
Balm 4%
Soap bar 4%
Foundation 6%
Cleanser 10%
Exfoliant 10%
Gel 10%
Mask 12%
Serum 16%
Cream 24%
Table 2. Cosmetic products and their ingredients. Data obtained from 50 products advertised by major retailers of cosmetics.* The ingredient listed as “Bifida ferment lysate” corresponds to a lysate from Bifidobacterium longum reuter.
These claims by themselves require critiquing. There is no single healthy skin mi-crobiome, so what would it take to ”balance” the one that a given individual possessed?Furthermore, the skin has many layers, with microbes being detected in the dermis, adi-pose, follicle, epidermis [8]. A product claiming to “balance” the microbiome should havestudies indicating in many subjects, preferably hundreds, how a given probiotic productchanges the various layers of microbiota in such a way as to restore and maintain it to whatis deemed healthy for each individual. Since it seems highly unlikely that such studies havebeen performed for most if any products, claims of balancing the skin microbiome shouldnot be made. This is important because consumers like the sound of products that do that,especially since terms like the “microbiome” and “balance” are being used so widely.
Enhancement of the skin’s overall appearance can be subjective for consumers, but italso has some scientific principles. Factors such as the reduction of the contrast, presence ofvisible ageing marks or spots, skin colour, melanin, and hemoglobin can be measured [9].This and other assessments provide the means to give tangible results that can then providesubstance to claims of improvements.
The ability of certain probiotic strains to improve epithelial and epidermal barrierfunction has been reported. The latter is so critical in the function of the skin and awell-used target for making claims that appeal to consumers. If strains being used ascosmetics do indeed improve barrier function, experiments can be performed to verify this.Indeed, researchers from a well-renowned cosmetic company have shown that a lysatefrom the probiotic Bifidobacterium longum reuter strain could decrease vasodilation, edema,mast cell degranulation, and TNF-alpha release, and using trans-epidermal water loss to
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assess barrier function, showed improvement with application of the lysate containingproduct [10]. 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 someother larger weight molecules (e.g., peptides). This might remove some of the bioactivecompounds of the preparation and components of the bacterial cells required to observespecific benefits. Therefore, filtrates are excluded from the definition of postbiotics andcannot be deemed to be probiotic.
Lysates are cells whose outer membrane has been broken down due to chemicalor physical processes [11]. These preparations have been used in medical practice asimmunomodulators for fifty years. They can contain bacterial components that up-regulatethe immune response of the host cells; they are particularly effective in the managementof infections of the respiratory tract [12]. Lysates of Lacticaseibacillus rhamnosus GG andB. longum can increase tight-junction barrier resistance in vitro by modulating proteincomponents [13]. Although there is value in using these types of preparations, furtherstudies are still required on a strain-dependent basis before drawing conclusions andmaking claims. The cell composition, elasticity, and activation of macrophages differbetween bacterial strains, even within the same species [14]. In one study, lactobacillilysates altered their ability to increase re-epithelialization of keratinocytes [15], againemphasizing the need to check strain properties prior to making claims.
Intriguingly, little has been reported on the chemical composition of the lysates beingused in cosmetics. This should require cell wall and analysis, including the use of liquidchromatography–tandem mass spectrometry (LC-MS/MS)-based metabolomics [16] ornewer methods such as surface-enhanced Raman spectroscopy (SERS) [17]. In doing so, itwill soon be extremely apparent that metabolite types and quantities differ between strains,and therefore their application to human tissues would also differ. This again illustratesthe need to perform tests in humans with whole microbial cells, lysates, or filtrates to showwhat activity is being promoted by the application of any given product; ideally to knowwhich component of the lysate is responsible.
There are numerous studies providing evidence of the benefits of specific probioticstrains for skin health [18–20]. In addition, the mechanisms of anti-ageing suggest strainscan help to regulate pH, reduce oxidative stress, protect from photoaging, and improve theskin barrier function [21].
However, the cosmetic industry needs to be consistent and transparent in its labellingpractices and direct efforts to generating more scientific evidence before making claims.
3. Topical Delivery and Formulation of Probiotics
Not all applications for skincare for males or females require local application. Orallyadministered probiotics have been demonstrated to affect the intestinal microbiome lead-ing to a potential improvement in skin conditions such as atopic dermatitis, acne, orrosacea [22,23]. Early studies suggested that probiotic use during gestation and early lifemay be required to reduce the incidence and adversity of atopic dermatitis [24], implyingimmune modulation and improving the maturing gut barrier function [25].
Freeze-drying of probiotic strains is commonplace. However, depending on the dryingprotectant used, final viability can vary. The most used protectants are skim milk, serum,trehalose, glycerol, betaine, adonitol, sucrose, glucose, lactose, and polyethylene glycol;these may not be compatible with the intended use of the product or the physicochemicalcharacteristics of the formula [26]. When using this method, the strains should not beexposed to water, otherwise they will prematurely rehydrate [27].
Microencapsulation is used to extend the shelf-life and viability of probiotics. It isprimarily to ensure that organisms resist the digestive system’s extreme environment [28],but it has been used in topical formulas [29]. Most commonly, the microbes are embeddedin a protective matrix of biopolymers or lipids.
It is challenging for the cosmetic industry to create topical formulas that retain probi-otic bacterial viability from production to the value chain and onto the consumer. Moisture
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would allow the dried organisms to hydrate and multiply or die, so oil-based formulationsare needed. The question becomes how easily the organisms can emerge from the oilonce placed on the skin, and thence become metabolically active sufficient to deliver theprobiotic effects required.
Many creams are not produced in sterile conditions, therefore preservatives are oftenadded with bactericidal and/or bacteriostatic effects. These potentially can not only affectthe probiotic strain viability but also inadvertently alter the microbiota of the recipient.
Regulation of probiotics is primarily concerned with safety. There is no specific re-quirement for commercializing probiotics, and products are regulated according to theirfinal use, whether it is as a drug, medical device, food, dietary supplement, or cosmetic.The descriptiveness and level of documentation required to claim a cosmetic probiotic issubstantially less than for one making drug claims in Canada and elsewhere [30]. Unfor-tunately, in a bid to maximize profit, some companies make disease or illness-alleviationstatements associated with their cosmetic products, when this should be reserved for drugsor clinically proven supplements.
Due to safety concerns, cosmetic products are expected to have a low content ofmicroorganisms (below 500 colony forming units (CFU)/g for eye-area products and1000 CFU/g for the rest) [31]. It is not a viable option for them to contain live bacteria,meaning that there cannot be a cosmetic that is a true probiotic. However, they can stillcontain components sourced from probiotic strains that could be beneficial. These can con-stitute bacterial lysates, ferments, and filtrates, sometimes referred to as postbiotics, definedas a “preparation of inanimate microorganisms and/or their components that confers ahealth benefit on the target host. [32]”. This definition does not include purified metabolitesor components without cells, which should instead be listed following their chemicalnomenclature. Filtrates without cell components are not considered postbiotics. However,bacterial lysates and ferments might fit into this category depending on their composition.
Biochemically, fermentation is an anaerobic metabolic process where carbohydrates(for example, lactose) are partially oxidized to generate energy for the cell, with lacticacid produced as a result. Fermented foods and beverages are defined as “foods madethrough desired microbial growth and enzymatic conversions of food components [33].This should not be confused with the ferments for skin application. In that case, the processof fermentation has taken place but not with respect to using or converting human food.Fermentation can be either an aerobic or anaerobic process in which a living organism (or itsenzymes) chemically modify a substrate to generate a product of interest [34]. Therefore, ifferments included in a cosmetic product contain viable probiotic strains, and if they remainlive until they reach the host target site, these products could potentially be marketedas probiotics.
Unfortunately, as shown in Figure 2, from the ingredients listed in the labels of the50 cosmetic products we analyzed (Table 2), none of them stated the strain designation ofthe microorganism included, and only 8% of the listed ingredients included the name of thespecies used. Those products listing the use of Bifidobacterium included it on their labels as“Bifida ferment lysate,” documented as an ultrasound inactivated suspension of Bifidobac-terium longum reuter in aqueous medium [10], which as previously described, can improvebarrier function as well as decrease skin sensitivity. Nonetheless, products containing thisingredient cannot be marketed as probiotics due to the absence of live bacteria.
In terms of the type of preparation, 78% of the ingredients listed on the labels corre-sponded to ferments, either as extracts, filtrates, or lysates. Yogurt is listed in 10% of theingredients, however, there is no information about the type of bacteria or substrate, nor isit indicated if it contains live bacteria. Finally, 12% of the products do not indicate the typeof preparation in which the microbial ingredients were included. Overall, the informationis vague and does not allow for a critical analysis of the potential probiotic or postbioticcharacteristics of the formula.
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With proper regulations in place, and potentially labelled as over-the-counter (OTC)drugs instead of cosmetics, there is value in the use of probiotics as topical treatments.Particularly, their antibacterial and immunomodulatory properties make them promisingcandidates to target skin ailments such as acne, psoriasis, and atopic dermatitis, as well asto aid in wound healing [35–39]. Nonetheless, further research in humans and randomizedclinical trials are still required to validate these potential uses.
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to aid in wound healing [35–39]. Nonetheless, further research in humans and random-ized clinical trials are still required to validate these potential uses.
Figure 2. Debrief of the ingredients listed in 50 cosmetic products. A total of 71 items listed in the ingredients label of the products were included in this analysis; waffle charts depict the pro-portion of each component as parts of a whole [40]. Panel A shows the frequency in which each microbial component was included. Panel B shows the frequency in which each type of prepara-tion was used in the products analyzed. Generated using R version 4.0.2. Percentages were rounded to the nearest whole number for ease of visualization.
4. Probiotics for Female Intimate Care
Figure 2. Debrief of the ingredients listed in 50 cosmetic products. A total of 71 items listed in theingredients label of the products were included in this analysis; waffle charts depict the proportionof each component as parts of a whole [40]. Panel A shows the frequency in which each microbialcomponent was included. Panel B shows the frequency in which each type of preparation was usedin the products analyzed. Generated using R version 4.0.2. Percentages were rounded to the nearestwhole number for ease of visualization.
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4. Probiotics for Female Intimate Care
A healthy vaginal environment is in most cases populated by an abundance of lacto-bacilli. Various triggers, from the use of douches and antibiotics to multiple sexual partnersand influx of pathogens into the area, disrupt the homeostasis giving rise to bacterialvaginosis, urinary tract infections, candidiasis, and other conditions. This provided a ratio-nale 48 years ago to supplement the urogenital tract with lactobacilli to restore a healthystate [29,41]. Since then, the vaginal administration of probiotic strains of Lactobacillusthrough suppositories or vaginal ovules has been explored [23].
Beginning with instilling Lacticaseibacillus (formerly, Lactobacillus) rhamnosus GR-1 intothe vagina [42], a range of strains have been tested, including Limosilactobacillus (formerlyLactobacillus) reuteri RC-14 and Lactobacillus crispatus CTV05 to reduce the recurrence ofurinary tract infection (UTI) [43,44], Lacticaseibacillus rhamnosus IMC 501 in combinationwith Lactobacillus paracasei IMC 502 to maintain vaginal homeostasis [45] and L. rhamnosusLcr35 for BV and vulvovaginal candidiasis [46,47].
Given the significant negative impact of antimicrobial therapy on the urogenital mi-crobiota and failure to restore homeostasis, probiotic strains have been used in combinationto help with recovery. These include Lactobacillus gasseri EN-153471 (EB01) for the manage-ment of BV [48] and L. rhamnosus GR-1 plus L. reuteri RC-14 in combination with antibioticsor antifungals [49–51]. Additional strains have become available in the American marketwith minimal clinical and scientific documentation [52].
The supplements are believed to function through ascension from the rectal skin to thevagina, where they reduce pathogen ascension and inhibit and displace pathogens whilealso conferring antimicrobial defences through the production of bioactive compoundssuch as lactic acid, hydrogen peroxide, and bacteriocins.
Therefore, these are essentially cosmetic in action on the skin, but they are promotedthrough a higher level of regulation where some functional and structural, or even diseaserisk reduction claims can be made. The application of strains directly into the vagina usingsuppositories that are applied vaginally is approved in Canada [53]. Other products arebeing delivered through coating tampons and pomades [54–56], but further evidence isrequired to confirm they are probiotic and benefit the host.
An emerging area is for probiotic strains to reduce urogenital malodor that signif-icantly impacts the quality of life of women, especially in combination with bacterialvaginosis [57]. Many non-probiotic products such as vaginal douches, vinegar rinses, andfragrances claim to help reduce malodor. However, their efficacy is dubious, and they canincrease the risk of infection, including sexual acquisition through disruption of the benefi-cial microbes [58,59]. An advantage of an effective probiotic would come from its ability togrow and produce metabolites that degrade or neutralize malodorous compounds [60,61].Depending on the nature of such a product, it may have to be registered as an OTC drugand not as a cosmetic or personal care product.
The development of topical gel containing probiotic lactobacilli is already underway,with promising results for treating vulvo-vaginal candidiasis [62].
It could be argued that applications in the urogenital tract do not strictly fall withinthe definition of a cosmetic, namely intended to restore or improve a person’s appearance.Likewise, applications for reducing halitosis [63–65] may also not fit, depending on how‘appearance’ is defined and interpreted. Whereas reducing acne symptoms with lactobacilliin a topical cream would fit as a cosmetic [66].
5. Conclusions
The recognition that certain types of microbes provide health benefits to the hostand that the human body and planet are literally filled with microbes, has brought newopportunities to the management of personal and ecosystem health. Companies in allspheres of business, including cosmetics, have taken advantage of this knowledge todevelop new products and increase profits. Terms such as probiotics, prebiotics, andmicrobiome were unheard of in cosmetic products a mere twenty years ago. Their use
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would be encouraging if it coincided with strong scientific research supporting claimsand uncovering the mechanisms of action of the strains and material being promoted.Unfortunately, this is rarely the case.
While chemistry is a mainstay of the cosmetic field, it has not been sufficiently wellapplied to identify the molecules responsible for the benefits provided by microbial prod-ucts. Given the expansion of the microbiome field, an emergence of microbiology andchemistry expertise will be needed to ensure high-quality cosmetics adherent to definitions(of a probiotic, prebiotic, etc.) are able to reach consumers.
There is no question that the modulation of microbes can lead to novel ways toimprove appearance and well-being. This will provide regulatory challenges as it bringscosmetic products into the health realm. While advocating the need for regulatory agenciesto upgrade their often-antiquated systems and categories, we need to insist on productsafety, clinical verification, and proof of using high standards for handling, storing andapplying products containing microbes and their metabolites or cell walls. Unprovenclaims help no-one, whereas good scientific investigation can bring forth products of greatmerit to human health and well-being.
Author Contributions: Conceptualization, S.P.-B. and G.R.; software, S.P.-B.; writing—original draftpreparation, S.P.-B.; writing—review and editing, G.R.; visualization, S.P.-B.; supervision, G.R.;project administration, S.P.-B. and G.R.; funding acquisition, G.R. All authors have read and agreedto the published version of the manuscript.
Funding: SPB is funded by the Mexican Council of Science and Technology (CONACyT).
Conflicts of Interest: SPB declares no conflict of interest. GR provides advice to SEED Health whichsells a synbiotic product not named in this paper.
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