Archaeologic evidence indicates that humans have been painting their bodies for nearly a half-million years,¹ progressing from sharpened reocher sticks presumed to be used for coloring the bodies of Homo erectus to modern cosmetics of such technical and esthetic sophistication. Although early cosmetic use of lead and antimony may have inadvertently served a preservative function, the realization of microbiological risk and need for preservation was largely a mid-20th century realization. The concept of microbiological quality and effective preservation developed early for foods but less rapidly for cosmetics. Despite the early 20th century introduction of parabens² and to a limited extent formaldehyde and benzoic acid,³ and the 1938 US Food Drug and Cosmetic Act, cosmetic preservation as a focused technical effort across the industry did not evolve until the latter half of the last century. Published reports that exposed the poor state of cosmetic and drug microbiological quality were compelling to its development. A US Food and Drug administration (FDA) study of products sold in New York found 25% to be contaminated with various bacteria and fungi.⁴ Other studies found similar levels of contaminated drug and cosmetics products in Europe.⁵,⁶ Preservation and preservative testing became important and necessary elements of cosmetic research and development addressing risks of contamination during manufacturing and preservative systems and protocols for their evaluation.⁷,⁸,⁹,¹⁰ By contrast, preservative testing developed to address pharmaceutical contamination focused on contaminants encountered in clinical practice.¹¹,¹² An additional concern for microbiological safety of cosmetics was identified by Ahearn et al who reported eye infections, some resulting in blindness, traced to contaminated mascara.¹³,¹⁴,¹⁵ The same products were shown to be free of contamination before use; however, consumer practices of moistening the mascara brush with tap water and spittle resulted in microbial growth on the brush and in the product. Minor corneal abrasion resulting from misuse of the brush, implanted Pseudomonas aeruginosa in a manner that resulted in serious ocular infection, blinding some women. The realization of in-use risk further compelled attention to preservative stability and efficacy through the life of the product.¹⁶ Dr. Ahearn’s investigation had been funded by the FDA, and the serious nature of these reports compelled the agency to propose rulemaking to establish regulations for the development of preservative efficacy standards for eye-area products.¹⁷

Through the following decade, the cosmetic industry organized as the Cosmetic, Toiletry and Fragrance Association (now the Personal Care Products Council or PCPC), developed and broadly implemented industry guidelines and methodologies to control microbiological risks. With the introduction of good manufacturing practices (GMPs), new preservatives and data-driven qualification of preservatives systems, microbiological concerns, recalls and risks of contamination diminished profoundly.¹⁸ Through the remainder of the 20th century, the cosmetic industry focused on maintaining this high level of microbiological quality by the reapplication of a few, very effective combinations of preservatives including esters of parabens, formaldehyde releasers (FAs), isothiazolinone, organic alcohols and acids and the adjunct ethylene diamine tetraacetic acid (EDTA).⁷,¹⁹ At the turn of the century, Darbre²⁰ published a troubling report that implied a connection between parabens and breast cancer, a phenomenon that lab and others continued to explore into the 21st century. Although this connection was and continues to be significantly criticized by the scientific community²¹ and has not been accepted by the FDA,²² it provoked closer scrutiny of parabens. The European Union later banned paraben esters of limited use primarily due to lack of current safety data.²³ As these molecules are commodities and the primary paraben was not affected, no supplier chose to invest data development. The overall safety assessment of parabens continues to support their safe use in cosmetics.²⁴,²⁵,²⁶
However, growing consumer desire for alternative and natural products²⁷ was unfavorable to all traditional preservatives, but most critical of parabens drove application of alternatives.²⁸,²⁹ The preservative methyl isothiazolinone was introduced as a replacement,²⁸ but its rapid and extensive adoption apparently proved problematic as it drove an unacceptable level of sensitization among consumers.³⁰,³¹ Although major companies have maintained traditional cosmetic preservative combinations,³² preservation diversified in the hands of some formulators to include more complex combination of less effective chemicals, some of which were largely new, as well as several “natural” preservatives and “preservative-free” packaging innovations.²⁸,²⁹,³³,³⁴ Unfortunately, these alternative preservative systems have, in some cases, driven cosmetic recalls due to microbial contamination at levels not seen for many decades. FDA reported over 70 cosmetic-specific cosmetic products recalled for microbial contamination in 2017.³⁵ All associated natural or alternative preservative systems, the greatest level this writer recalls in his 40-year career. The following sections will address the rationale for preservative use, the scope of preservation, preservatives and preservation elements, and the methods and risk assessments used by the cosmetic industry to ensure consumer safety.