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J. Cosmet. Sci., 75.5, 483–523 (September/October 2024)
*Address all correspondence to Donald S. Orth, orthconsulting@msn.com
The Evolution of Cosmetic Preservation and the
Microbiological Challenges Posed by Sustainability
DONALD S. ORTH,
Orth Consulting, LLC., Maineville, Ohio, USA
James L. Winkle College of Pharmacy, University of Cincinnati. Cincinnati, Ohio, USA
Accepted for publication July 8, 2024.
Synopsis
Cosmetic preservation has been evolving over the past 75 years. This review discusses changes in the use
of preservatives, including how the use of hurdle technology has enabled cosmetic scientists to formulate
products with reduced levels of preservatives or that are preservative-free, and how cosmetic preservation has
expanded from being focused just on preservative systems that prevent product contamination to products
that are sustainable because they preserve the environment and the healthy skin microbiome. There are still
gaps in our knowledge that need to be addressed to ensure that future products are adequately preserved, that
they do not encourage development of antibiotic-resistant microorganisms, and that they work with the skin
microbiome to maintain homeostasis.
INTRODUCTION
Cosmetic microbiology is a discipline within cosmetic science. A major objective of cosmetic
microbiology over the past 75 years has been to reduce or eliminate microbial contamination
of cosmetics in over the counter (OTC) drug products. This has been largely addressed by
preservative efficacy testing to demonstrate that formulas are adequately preserved for the
packaging and intended consumer use, by validating procedures used in the manufacturing
plant to maintain microbiological control, by finished product testing that is performed
correctly, and by use of appropriate microbiological release criteria to ensure that products
leaving the manufacturing plant are not contaminated with microorganisms that are able
to grow in the product.
A second goal of cosmetic microbiology has been to develop and use test methods that
are faster, more reliable, more environmentally friendly, and less expensive than the
microbiological test methods that have been used for decades. Such test methods expedite
product development and finished product release, with assurance that the test methods
are better able to recover stressed or metabolically injured microorganisms. This virtually
eliminates the growth of microorganisms in products that were initially tested and found
to meet microbial release specifications. Finding unacceptably high microbial counts in

484 JOURNAL OF COSMETIC SCIENCE
finished products days or weeks after product release testing indicated that the products
were within microbiology release specifications often is referred to as bacterial “rebound,”
or the Phoenix Phenomenon.1
A third goal of cosmetic microbiology has been to work with formulators to develop
preservative-free (e.g., self-preserving) products to meet consumer desires for products
that are more consumer friendly, environmentally friendly, and sustainable. Marketing
departments are asking cosmetic scientists and microbiologists to meet consumer demands
for safety and sustainability with products that do not contain preservatives, fragrances,
dyes, toxic chemicals, or packaging that are not biodegradable.
A more recent goal of cosmetic microbiology has been to conduct tests to better understand
the role of skin microflora (e.g., the skin microbiome), to include identification of beneficial
microorganisms, the interactions of these microorganisms with skin and mucous
membranes, and the effects of topical products on the skin microbiome. We are learning
from studies using probiotics and prebiotics to modulate the intestinal microflora, and it
is possible that selected microorganisms and ingredients will benefit desirable commensal
microorganisms in the skin microbiome.
The objective of this review is to discuss the evolution of cosmetic preservation. The
history of microbiology describes scientific advancements that provided the foundation for
the development of cosmetic microbiology. The changing use of preservatives involves a
transition from products with traditional preservatives to products that are preservative-
free. Studies of the skin microbiome are an active area of research in which we are learning
what microorganisms are on the skin and how they interact with each other and with the
skin to maintain homeostasis. It is anticipated that future studies will reveal the effect of
preservatives and products on the skin microbiome. Gaps in our knowledge need to be
identified and addressed in future products to ensure that products are sustainable because
they are adequately preserved, and that they have no adverse effects on the environment
or the skin/skin microbiome ecosystem. In this review, “cosmetic” refers to both color
cosmetics and toiletries.
HISTORY OF MICROBIOLOGY
Long before people knew about microorganisms, there must have been a belief that
something was happening when products spoiled by turning green or black and by
developing off-odors. People learned that some chemical agents were able to help preserve
water, foods, and other products. Hugo described the practice around 450 B.C. of keeping
water potable by storing it in copper or silver containers.2 Salts, oils, and natural balsams
were used for mummification. Over centuries, people learned that foods and other materials
could be preserved by means of salting, drying, fermenting, acidifying, and adding herbs,
honey, and natural spices. These methods of preservation were learned by experience and
were used even though people did not know about the existence of bacteria or other types
of microorganisms.
Microbiology today has evolved from the discoveries of physicians and scientists in Europe
and Asia up through the 19th century. These workers included Leeuwenhoek (used single-
lensed microscopes to observe microbes commonly known as “the Father of Microbiology”),
Pringle (used different salt solutions to prevent meat spoilage—considered to be a
forerunner of tests for the minimum inhibitory concentration of preservatives and other