By Lambros Kromidas, PhD and Balint Koroskenyi, PhD

Multifunctionals are cosmetic ingredients that offer a variety of benefits to a personal care product. Examples of multifunctional ingredients include 1,2-alkanediols, hydroxyacetophenone, ethylhexylglycerin and propanediol benzoate, among others. Their primary function in the formula is to enhance the quality, stability, or performance of the product. Although they are used for their primary function, multifunctionals also have an important secondary function, and that is, to support product protection against microbial contamination. 

Multifunctionals are important to formulators because they can lead to streamlining the product development process, reducing formulation complexity and simplifying the ingredient list on the label, thereby supporting minimalistic formulation goals. But more importantly, multifunctionals offer flexible options to formulators to build robust product protection systems, especially as regulatory restrictions and consumer concerns limit the use of certain preservatives. 

Traditionally, preservatives have been used in microbiologically susceptible cosmetic formulations to ensure product protection. However, as time moves on, for one reason or another, the use of conventional preservatives is becoming increasingly restricted (for the most part, by regulatory mandates and public scrutiny). Therefore, having alternatives and complementary approaches in a formulator’s arsenal have been gaining widespread use. Multifunctionals fit that bill and as a result, they have been growing in importance in recent years.

The Preservation Stewardship Task Force of the Personal Care Product Council (PCPC) completed a white paper on multifunctionals that was published on the PCPC website in June 2025 entitled, “Multifunctionals for the Microbiological Protection of Cosmetics and Personal Care Products.”¹ 

This PCPC white paper¹ is meant to serve as an informational overview on ingredients that offer multiple beneficial functions in a formulation, including the ability to support antimicrobial product protection, i.e., multifunctionals. The white paper also provides insight into benefits and limitations in formulating them. It attempts to provide clarity and define the terminologies used, as well as other aspects related to the use of these ingredients. We will highlight some points here and encourage readers to view the full PCPC white paper.¹

Antimicrobial Effectiveness

A key issue for cosmetic/personal care products is to protect the formula, and in turn the user, from microbial contamination once the product has been placed on the market. Antimicrobial protection is usually achieved with the help of cosmetic ingredients that support the inhibition of microbial contamination. Some ingredients, known as preservatives, are designed and used for that particular purpose. However, there are other aspects of cosmetic formulations that influence this ability. That includes other cosmetic ingredients that are inherently not friendly to microorganisms as well as formulation type, water activity, and pH just to name a few. Packaging and how the formula is dispensed is also important in minimizing contamination. 

Antimicrobial effectiveness in a formula is typically determined by inoculating it with a known set and quantity of microorganisms and then monitoring survival time—commonly over 28 days. This is known as Preservative Efficacy Testing (PET). This exercise ensures that the antimicrobial activity by the overall formula (i.e., all contributing factors as discussed above) is sufficient to combat against microorganisms that may be inadvertently introduced into the product, especially during consumer use.

There are several official PET methods such as that of the International Standards Organization (ISO),² the United States Pharmacopeia,³ and the European Pharmacopeia.⁴ In addition, a PCPC method can be obtained through PCPC’s online bookstore. A manufacturer may also develop a customized method to meet their specific needs.

Multifunctional ingredients are, as mentioned above, ingredients not inherently friendly to microbial growth and formulators may use them to “feed two birds with one scone” – i.e., provide a cosmetic benefit and enhance antimicrobial effectiveness. Of course, different multifunctional ingredients have different levels of antimicrobial effectiveness. Some may be more effective against bacteria than fungi, or vice versa. Others might primarily target Gram-negative bacteria but display minimal activity towards Gram-positive bacteria. In a formula, they can contribute to an overall faster rate of microbial count reduction or help to achieve a broader spectrum of protection. They may also reduce the dosage of traditional preservatives or support their replacement with a safer or more desired alternative. Further, a formulation that may have challenges with a specific test organism could benefit from a multifunctional by having a more targeted efficacy against the microbe of concern.

It is important to reiterate that the antimicrobial effectiveness in a cosmetic product is a combined effect of the whole formulation rather than any individual ingredient, and that other components of the formulation can also influence the antimicrobial efficacy aside from preservatives or multifunctionals.

The same approach used to assess the antimicrobial effectiveness of conventional preservatives can be used when evaluating multifunctional ingredients.

Formulating with Multifunctionals

Formulating with multifunctionals is like formulating with other cosmetic ingredients, but there are some considerations to keep in mind.

Although some preservatives may be used at <0.1%, multifunctionals are typically used above this concentration, especially for formulation types like surfactant solutions, sunscreens, or wet wipes. 

Multifunctionals may be added at various stages in the process of creating a formulation. The order of addition of any ingredient is determined by factors, such as solubility, temperature stability, pH, lipophilicity, etc.

In a single aqueous phase formula, water-soluble multifunctionals are simply dissolved. If water-insoluble, it can be dispersed by first solubilizing in a water-miscible solvent. In biphasic formulas, the hydrophilicity/lipophilicity of the multifunctional determines its partitioning in the phases. Since generally microorganisms prefer an aqueous microenvironment, only multifunctionals present in the aqueous phase (i.e., hydrophilic) would be most active.

With regards to emulsification, certain multifunctionals may contribute to the emulsification process or the emulsion stability, while others might have a destabilizing effect. 

For suspensions, particular care must be taken to prevent adsorption of the multifunctionals on the surface of the solid particles, which may result in reduced efficacy. This can usually be achieved by allowing other formulation ingredients to coat the solid particles before the multifunctionals are added. 

As with any other ingredient, the order of addition in the manufacturing process should be considered. For example, multifunctionals should be added to the formulation after any process steps that involve temperatures higher than the stability of the ingredient. When emulsions are prepared at elevated temperatures, multifunctionals are recommended to be added to the cool-down phase. In cold processing, multifunctionals can be added directly into the water phase or added after the emulsion has been formed. For suspensions, emulsifying agents should always be allowed to coat solid particles before adding any multifunctional to reduce the risk of adsorption of the ingredient on the particles. Finally, if the multifunctional is hydrolytically unstable at the pH level of one of the process steps, this should be considered. In some cases, formulation pH may have major impacts on antimicrobial efficacy. For hydrolytically less stable chemical classes, such as esters, hydrolysis may take place at acidic or alkaline pHs. This must be considered when there are process steps with pH values outside the ester stable pH range (typically 4-8). 

Multifunctionals that are organic acids or chelating agents are also pH dependent. Organic acids must be in the protonated, uncharged form to be effective. Organic acids have a chemical equilibrium with their negatively charged conjugate bases. This equilibrium gets shifted towards the charged conjugate base as the pH increases. Therefore, at a high enough pH, the relative amount of neutral protonated form becomes insufficient to provide effective antimicrobial protection support. Lastly, at acidic or alkaline pHs, antimicrobial product protection is enhanced by weakening the microorganism’s cell wall, and therefore permits lower multifunctional use levels.

For a more in-depth discussion and additional considerations in formulating with multifunctionals, the reader is encouraged to download the white paper¹ from the PCPC website.

Conclusion

As preservatives options are becoming more limited due to safety concerns, stricter regulations, and often unsubstantiated publicity, cosmetic formulators can use all the help they can get from ingredients that are not microbe friendly. Multifunctionals used for cosmetic purposes can support formulators in that respect⁵ while meeting consumer expectations for safe products. It is advisable for the formulator to assess the effectiveness on the finished product level and overcome potential formulation hurdles as discussed above. The referenced white paper¹ also discusses sustainability aspects of multifunctionals.

References

1. PCPC Microbiology Committee. Multifunctionals for the Microbiological Protection of Cosmetics and Personal Care Products, PCPC Scientific Papers, June 2025, https://www.personalcarecouncil.org/resources/scientific-papers/.
2. ISO 11930:2019, Evaluation of the antimicrobial protection of a cosmetic product.
3. USP, 2019: United States Pharmacopeia, USP <51> Antimicrobial Effectiveness Testing, 2019. 
4. European Pharmacopeia, EP 5.1.3 Efficacy of Antimicrobial Preservation. European Directorate for the Quality of Medicines & Health Care, 2019.
5. Juncan, A. M., Rus, L. L., Craciun, V. I., & Tincu, A. L., Morgovan, C. Application of a multifunctional additive in cosmetic preparations for safe preservation. Revista de Chimie, 70 (2019), 2429.

ABOUT THE AUTHORS

Lambros Kromidas, PhD, is VP-global legal regulatory affairs liaison at Shiseido. Prior, he held management positions at Avon, Coty, Beiersdorf and RIFM. He received a MS in microbiology and PhD in toxicology from St. John’s University (New York) and conducted post-doctorate research at Cornell University Medical College, Department of Physiology. He is a member of SCC, SOT and an active PCPC participant.  

Balint Koroskenyi, PhD, is scientific and technical director at Symrise. Prior to his current role, he worked in personal care as a bench chemist, a technical account manager and a product manager. Since 2022, he has been a co-instructor of an SCC continuing education course on preserving personal care formulations. He has a MS in chemistry and a PhD from the University of Massachusetts-Lowell and is a member of SCC and PCPC. 

The viewpoints expressed in this paper are solely those of the authors and do not necessarily reflect those of any competent authority, PCPC, or company. The purpose of this article is to guide and inform the reader. The reader is encouraged to verify any opinions and facts the author presents.