486 JOURNAL OF COSMETIC SCIENCE
This book helped create a more scientific approach to the development and manufacture
of cosmetics. The importance of microbiology was becoming more recognized, parabens
were the preservative of choice, and preservative testing used cultures of test bacteria. The
Society of Cosmetic Chemists was founded in 1945. Visible mold contamination was the
primary cause of recognized product defects in the 1940s.4
In the 1950s, microbiologists were involved with testing new antimicrobials to determine
their antimicrobial spectrum (i.e., which types of bacteria, yeasts, and molds they inhibited)
and concentrations needed for product preservation. In-use panel tests were conducted to
determine substantivity and antibacterial activity for product claim support. Preservation
studies included testing for incompatibility with ingredients and the effects of pH,
packaging, and storage conditions however, there were no standardized microbiological test
methods for preservative efficacy at this time.4 Curry noted that scientists were becoming
aware of the growing problem of bacterial resistance.4
In 1965, Kallings, Ernerfeldt and Silverstolpe6 reported microbial contamination of
nonsterile pharmaceuticals and selected toiletries in their report to the Royal Swedish
Medical Board.6 Kallings and coworkers identified the need to improve microbiological
controls during manufacturing and the need to improve the preservative systems of
aqueous products. The report was a “call to action” for the entire cosmetic industry because
it revealed that some marketed products were contaminated with bacteria, yeasts, and
molds. Although many companies had microbiological programs in place at the time, this
report demonstrated the need for improved microbiological controls in manufacturing and
the need for adequately preserved products. In the following years, governmental agencies
and independent testing laboratories conducted surveys to determine the type and extent
of product contamination.
In a presentation at the Toiletry Goods Scientific Conference in 1969, Wolven and Levenstein
reported that 61 out of 250 (24.4%) unopened cosmetic product samples examined were
contaminated with microorganisms.7Thisreportalarmedmanufacturersandregulatoryofficials
because bacterial contamination of products can have adverse health effects for consumers.
The Cosmetic, Toiletry, and Fragrance Association (CTFA) Microbiology Committee and
the Quality Assurance Committee developed guidelines for the cosmetic industry. Many
manufacturers incorporated these guidelines into their standard operating procedures.
In 1971, the FDA advised manufacturers that contaminated products were in violation
of the Food, Drug, and Cosmetic Act and that bacterial contamination could result in
“regulatory action” including seizure (i.e., placement of goods under quarantine by a federal
marshal), injunction (i.e., regulatory control that prevents a manufacturer from introducing
goods into interstate commerce), and/or criminal prosecution (i.e., legal proceedings that
could result in fines or imprisonment).3 Manufacturers reviewed their microbiological data
and improved product preservative systems, as needed.
Wolven and Levenstein conducted a follow-up survey in 1972 in which they found 8 out of
223 samples (3.6%) were contaminated.8 The microorganisms recovered from these samples
were Gram-negative rods (6%, including 0.5% pseudomonads), Gram-positive rods (5%),
and molds (0.4%). In addition, a CTFA survey from 1972–1975 tested 3,967 cosmetic and
toiletry products and found that 97.7% of them were “essentially free” of microorganisms
and that no Staphylococcus aureus, Escherichia coli or Pseudomonas aeruginosa were recovered in
any of the samples examined. These results showed that the industry had improved their
microbiological practices.3

487 Evolution and Challenges of Sustainability
Wolven and Levenstein also performed challenge tests and concluded that “regardless of
the method employed to demonstrate preservative efficacy, no growth should occur after
seven days.”8 This is an important point because it means that preservative efficacy testing
should show a ≥6-log reduction in 7 days. The follow-up test conducted by Wolven and
Levenstein also revealed that liquid eyeliners were contaminated.
Surveys were performed to determine if eye-area cosmetics were contaminated. In 1975,
Wilson, Julian, and Ahearn found that eye-area cosmetics generally were not contaminated
when sold, but that they became contaminated during use by consumers.9 It was alarming
to find Pseudomonas spp. in eye-area products because these microorganisms may cause
serious eye infections. Ahearn et al. reported that mascaras containing only parabens or
imidazolidinyl urea appeared to be less effective in preventing microbial growth than
mascaras preserved with mercury-containing preservatives.10 These findings helped
provide support for regulatory approval of mercury-containing preservatives such as phenyl
mercuric acetate in eye-area cosmetics in the United States.11
The two decades after the report by Kallings and coworkers were designated as the “Golden
Age of Cosmetic Microbiology” because it was a time in which many microbiologists were
employed to conduct surveys of cosmetic and pharmaceutical products, improve compliance
with current good manufacturing practices (GMPs), perform preservative efficacy tests to
ensure that products were adequately preserved, and conduct studies in support of OTC
drugs. During this time, the United States Pharmacopoeia (USP) published methods for
assessing the adequacy of preservation12 and the CTFA Microbiological Committee (now
the Personal Care Product Council [PCPC] Microbiological Committee) recommended
preservative efficacy testing guidelines with samplings at 1 or 2 days, and at 7, 14, and 28
days.13 USP and PCPC methods of preservative efficacy testing are in use today.
Formulators learned what worked in their formulations by experience, and combinations of
preservatives—typically methylparaben (MP) and propylparaben (PP) with a formaldehyde
donor—were the most popular preservatives used in cosmetics. Preservatives that have been
used frequently in cosmetic and drug formulations from the 1970s to date are presented
in Table I.
When discussing preservatives, it often is helpful to consider their functionality in terms of
preservative class (e.g., organic acids and their salts, paraben esters, quaternary ammonium
compounds [QACs], formaldehyde donors, alcohols, organic mercurials, and miscellaneous),
because this is a way of relating chemical structure with the antimicrobial spectrum,
advantages, and disadvantages of the different types of preservatives.14 Classes of many
preservatives along with their advantages and disadvantages are presented in Table II.
Products marketed in the 1970s and after generally have been well-preserved. Creams,
lotions, and shampoos made by several major cosmetic companies were purchased, and
preservative efficacy tests were performed on them. The products tested were adequately
preserved because the preservative systems in these products killed the test bacteria quickly
(e.g., preservative systems killed 106–107 cfu/mL of some test bacteria within a couple of days
and all bacteria along with 105–106 cfu/mL yeasts and molds were killed within a week).15
These products met the preservative requirements set by Wolven and Levenstein8 because
they showed no growth of the test organisms after seven days. Frequently, P. aeruginosa was
not recovered at any time point during preservative efficacy testing—not even initially
at the time 0 sampling (i.e., within 5 minutes after inoculation). It was later learned that
MP and chelating agents including acrylic acid homopolymer/copolymers or EDTA, which