In satisfying the regulatory and ethical demands for effective preservation through consumer use, formulators and marketers face a dilemma. Application of historically-effective, traditional preservative systems are discouraged by consumer and retail demands for alternative systems driven by perceived safety concerns and claims of green/natural/sustainable products. However, these alternatives are generally less effective and have driven in some applications significantly increased reports of microbial adulteration. This summarizes and discusses perspectives of a panel of preservative suppliers and service providers regarding efforts to serve this growing consumer segment that are availbale at this link, while the following commentary article by Dr. Phil Geis addresses and compares traditional preservatives and alternative systems, identifying risks that must be managed in their continued development and application.

SYLVIE CUPFERMA on behalf of Cosmetics Europe Expert Team in Product Preservation

SYLVIA NEFKENS Technical market specialist Home and Personal Care, Celanese

TOM FRICKE Manager Technical Application Cosmetics EMEA, Clariant

PETRA SCHAAL Application Development Manager Preservatives, Clariant

FRANCESCO TURSI Laboratory director, CompLife Italia

ROSANNA STOKES Business Development Manager, Emerald Kalama Chemical

FERNANDO IBARRA Managing Director, Evident Ingredients

ARIANNA FILIPPINI Product Manager Formula Protection, ROELMI HPC

SHAHEEN MAJEED President, Sabinsa

Nicola D'Anzi

Savio Industrial S.r.l. | Italia

Preservatives are an essential element of cosmetic microbiological quality.  Necessary but not sufficient to control contamination, they must be accompanied by appropriate good manufacturing practices (GMPs), manufacturing hygiene and protective packaging to achieve the primary goal – consumer microbiological safety.  In the manufacturing context, GMPs and manufacturing hygiene are the primary tools for microbiological quality with preservatives as necessary agents to mitigate contamination risks due to inadvertent and limited microbial exposure during production.  Failure in these can result in product contamination, significant not only to brand and regulatory compliance but also establishing significant consumer risks. At greatest risk are those with compromised immunity who can suffer serious infection possibly leading to death (1).

However and as observed by Francesco Tursi of Complife Italia, the primary role of preservation is to control contamination introduced during and through consumer use. This objective is regulatory policy and confirmed in practical impact as consumers have suffered blindness and even death following infection traced to cosmetics contaminated in use (2, 3).

In that role, preservatives are the only cosmetic ingredients used exclusively to satisfy a safety objective. Despite this essential role, preservatives are perhaps the least understood and most reviled of cosmetic ingredients. Traditional preservatives including parabens, formaldehyde-releasers, isothiazolinones and organic alcohols used in combinations from mid-20^th century until now have experienced the greatest negative attention.  As observed by Tom Fricke of Clariant, the rise of marketing claims such as natural, green, sustainable and “free-from” have impacted the use of these core ingredients as consumer preference for products bearing such claims has grown substantially.  The traditional preservatives as these are synthetic and some petroleum based, making them ready marketing targets. As observed by Rosanna Stokes of Emerald Kamala Chemical, some mass retailers have discouraged and even banned marketing of products including some of these preservative ingredients.

Dr. Ibarra of Evident Ingredients recalls the mythical silver bullet  - the ideal preservative based on perfection of antimicrobial efficacy, cost, safety, environmental fate, etc.  This has clearly not been satisfied. Of these, efficacy is the focus on this discussion. Preservatives as formulated in combination, must effectively mitigate risk for Gram positive bacteria such as Staphyloccoccus aureus, Gram negative bacteria such as Escherichia coli and Pseudomonas aeruginosa, yeast and mold. This efficacy is specifically evaluated in a compendial preservative challenge test such as the relevant  PCPC, USP, ASTM or ISO protocol.  As consumer protection through the entire product use is their primary preservative objective, many use ad hoc, in house tests validated to consumer use (e.g., 4).

Considered here are the primary preservatives parabens, formaldehyde releasers, isothiazolinones and organic alcohols with organic acids typically used as secondary preservatives in combination.  Although paraben have been used since early in the 20^th century, the above group of materials was largely developed and applied in the latter half of the 20^th century.  Used in combinations with synthetic chelator, developed manufacturing hygiene and appropriate packaging, these established a substantial record of microbiological quality.  Many major marketers continue to use these traditional preservative systems presumably based on their internal risks assessments and perspective of consumer safety. Additional considerations driving continued use of traditional preservatives include their established safety-in-use profiles, consistent efficacy across and between formulas variations  and regulatory compliance in those regions that specifically list allowable preservatives. Although parabens and formaldehyde releasers current garner the greatest negative attention, all these primary preservatives are at risk again despite their generally-accepted safety in use.  It is noteworthy that traditional preservatives with developed manufacturing controls established a record of excellent microbiological quality recognized by the US FDA.

Certainly, many preservatives and preservatives combinations are offered as alternatives to the traditional systems.  One group of alternative preservatives is composed of “natural” preservatives. Preservation using materials obtained unchanged in chemical composition from nature is a very problematic effort.  In the cosmetic context, this involves expensive, niche ingredients of limited efficacy, many of undefined and potentially inconsistent composition and purity. At least one preservative considered to be natural has been exposed as adulterated with synthetic biocides.  As composition of preservatives obtained directly from nature is typically complex and specific chemical responsible for efficacy is not defined, batch-to-batch compositional differences bring concern for inconsistent efficacy.  For botanical ingredients such as essential oils, contamination with pesticides can be a concern and scale up of supply to meet the needs of a global marketer must address concerns for expanded cultivation of invasive plants and social concerns.  Sylvai Nefkens of Celanese notes single antimicrobial compounds such as the traditional preservatives Benzoic and Sorbic acids and Benzyl alcohol can be purified from natural sources.  However, sourcing on an industrial scale is simply not practical.  In fact, magnitude of supply for preservatives obtained unchanged from nature is unlikely to satisfy the demands of any major global brand.

However, the definition of “natural” finds variable consideration. Ms. Nefkens notes the effective definition of “natural” in some considerations such as those of COSMOS and ISO 16128 addresses the use of synthetic production of materials found in nature.  Termed by some as “naturally compliant”, the preservative status of “natural” has been effectively established via credentialing organizations.  For example, synthetic petroleum based preservatives such as Benzoic and Sorbic acids and Benzyl alcohol are established as effectively “natural” in claims by the organization based on their parallel presence in nature.  In some marketing efforts, the concept is extended to materials obtained from nature and subsequently modified in chemical composition such as Sorbitan and Glyceryl caprylates and Capryl hydroxamic acid. Whether natural or naturally compliant, these preservatives with preservative boosters are less effective than traditional preservatives and so are used typically at higher concentrations and in more extended combinations. 

Ms. Stokes emphasized application of the “Hurdle concept” in preservation.  Here, a product is preserved by extended combinations of antimicrobial factors including but not limited to recognized preservatives.  Whereas traditional preservatives typically use two or three recognized primary preservatives, products preserved by the Hurdle concept may use a few chemicals of materials of limited preservative capacity combined with formulation factors such pH, water activity, surfactant concentration, chelators, increased manufacturing controls, protective packaging and other factors that mitigate risk of microbiological contamination.  The concept of multifunctional materials, ingredients serving cosmetic functions that also possess antimicrobial efficacy.  Dr. Ibara referred to this process in context of an established “toolbox” with alternatives and antimicrobials specific to formulation needs.

A final alternative concept is expressed in the claim “preservative-free.”  Virtually all aqueous (water containing) cosmetics require preservation. Whereas some products bearing this claim are indeed at substantial risk for contamination, others use antimicrobial ingredients not listed and established as “preservatives” in official regulatory documents.

A unique aspect of preservation and product quality was identified by Shaheen Majeed of Sabinsa– direct and indirect impact of preservatives on the microbiome.  Arianna Filippini of ROELMI HPC extended this concern to preservative effect of efficacy of microbiome directed, pre and probiotic products. Whereas the impact of long term cosmetic use on skin microbiome is a subject of ongoing research, Ms. Filipinni presented data addressing the immediate impact of preservatives on the efficacy of prebiotic cosmetics.  Even more problematic is preservation and product quality of probiotic products – those formulated to offer effective populations of living microorganism to skin.  Microbial contamination of probiotic nutritional products has been reported, in some cases resulting in serious and even fatal infections (5, 6).  Such risk will certainly require management in probiotic cosmetic products. However, even if intensified GMP and manufacturing hygiene controls adequately mitigate potential contamination in cosmetic production, the question of contamination in use must also be addressed and without compromising viability of the probiotic active microorganism.  

This risk mitigation effort does not lend itself to traditional methods.  Dr. Sylvie Cupferman on behalf of Cosmetics Europe observed the challenge documented by EU Scientific Committee for Consumer Safety notes of guidance from 2021 “Total germ count and challenge tests are not directly applicable for the case of probiotic cosmetic formulations to which live or viable microorganisms have been intentionally added.”

Traditional preservatives face strong consumer preference and marketing heads winds against which industry’s preservative defense efforts have shown little success.  However, alternatives currently available bring diminished efficacy, substantial complexity, and an increasing record of microbiological quality failures. So, what has the cosmetic industry done in response? Many major marketers have maintained the use of traditional preservatives.   Despite of growing consumer interest in alternative, especially natural, preservatives, apparent interpretation of responsibility for consumer safety in context of corporate risk assessment fails to find alternatives of sufficient efficacy in their products.  As judged by records of enforcement for cosmetics, traditional preservation was associated with a substantial record of microbiological safety from the latter decades of the 20^th century to now.

Whereas some maintain traditional preservatives, there are clearly forces from consumer-perceived safety concerns that drive to alternative systems.  These are available and apparently can successfully establish microbiological quality despite comprise in efficacy.  However, application of such alternatives has not maintained the record of microbiological safety established by traditional preservatives.  Contamination of such systems continues to dominate cosmetic enforcement reports (7) with numbers in one pre-covid year the greatest this 40 year veteran of the industry can recall.  Dr. Ibarra also noted an additional challenge - the extremely limited supply of preservation technologists with expertise to effectively establish alternative systems.  Unlike the academic programs of food microbiology and the extended professional literature base and training of pharmaceutical microbiology, cosmetic microbiology is an arcane practice that can only be learned in practice and application.  Clearly, the industry faces challenges in defending the appropriate and safety in use of traditional preservations and the appropriate application of alternatives systems, especially in the broad concept of natural/natural identical ingredients (8). 

*Article previously published in HPC Today, July/August 2021, Vol 16(4)

PANEL DISCUSSION

EDIZIONE SPONSORIZZATA DA

PHIL GEIS

Geis Microbiological Quality | United States