28 TESTING
scope of use. Proper handling is qualified by adherence to Good Manufacturing Practice (GMP) standards, which mandate aseptic technique, environmental monitoring, and qualification of equipment and personnel.10 Intrinsic qualities of a formulation that
may present as hurdle effects are largely physicochemical: these include raw material components and overall composition, e.g. the presence of chemicals that are hostile to microbial growth, a low free water activity, or pH control.11 Interaction between different hurdle effects
within a formulation may justify a reduced scope of microbiological monitoring and quality control practices - if permitted by other factors covered in the risk assessment – most notably, vulnerabilities introduced during the product’s use case.
Consumer profiling Considering the primary goal of a microbiological risk assessment is to protect the end-user throughout the product’s lifespan, it is necessary to identify a customer demographic and applicable vulnerabilities. This consumer profile may be defined by marketing strategies and should be considered in labeling (including directions for use). Products that are specifically intended
for children under the age of three, for example, may have a lower microbial limit
TABLE 1: MICROBIOLOGICAL LIMITS FOR COSMETICS DEFINED IN ISO 17516 Types of microorganisms
Products specifically intended for children under three years of age, the eye area or the mucous membranes
Total Aerobic Mesophilic Microorganisms (Bacteria plus yeast and mould)
Escherichia coli
Pseudomonas aeruginosa Staphyloccocus aureus Candida albicans
a b
>200 CFU/g or ml, >2000 CFU/g or ml
NOTE When colonies of bacteria are detected on Sabouraud Dextrose agar, Sabouraud Dextrose agar containing antibiotics may be used.
threshold compared to products released for a general population. Products with purported therapeutic benefits or first-aid indications that may be used by wounded, sick or elderly demographics may similarly adopt more stringent permissible limits. The route of administration must also be
considered: products that are to be applied to the eye area or other mucous membranes might be evaluated by different criteria than those designated for topical or oral use.
TABLE 2: AGGREGATED ACCEPTANCE CRITERIA DEFINED BY PERSONAL CARE PRODUCTS COUNCIL (PCPC), UNITED STATES PHARMACOPEIA (USP), INTERNATIONAL STANDARDS ORGANIZATION (ISO), AND EUROPEAN PHARMACOPEIA (EP) REFERENCES12-15
Reference PCPC Yeast/Mould
USP <51> Category 2**
Reference Bacteria N/A Yeast/Mould Organisms Bacteria B A ISO 11930* Yeast B A Mould B A Bacteria B EP 5.3.1.2.
Yeast/ Mould
A B *No increase is defined as an increase of no more than 0.5 log10 PERSONAL CARE May 2024 N/A ≥2 LR from initial ≥ 3LR from initial N/A N/A Criteria A Day 2 Day 7 Organisms Bacteria N/A Day 2 Day 7 Day 14
>3 LR from initial No increase from D7
>1 LR from initial No increase from D7
≥2 LR from initial
No increase from initial
Day 14
≥ 3LR from initial No increase from D7
N/A
≥ 3LR from initial
≥1 LR from initial No increase from D7
≥1 LR from initial
No increase from initial
N/A
≥ 3LR from initial
≥2 LR from initial
≥1 LR from initial
Day 28
No increase from D14
No increase from D14
No increase from D14
No increase from D14
Day 28
No increase from D14
No increase from D14
No increase from D14
No increase from D14
No increase from initial ≥1 LR from initial
No increase from D14
No increase from D14
No increase from D14
No increase from D14
No increase from D14
Further, demographic factors such as the
region of sale may inform microbiological quality regimens, with respect to regulatory compliance and to storage conditions for transit and use – materials may endure extended stress conditions in transit, or be distributed in regions with temperature and humidity patterns that are not representative of conditions at formulation. The effect that environmental stress
conditions exert on a formulation’s resistance to microbial growth can be assessed through stability testing, which may include accelerated aging and/or freeze-thaw cycling.
Defining limits The end result of a microbiological risk assessment is having defined permissible limits: pass/fail thresholds for the microbial content and preservative efficacy of a formulation. Despite the diversity in products under the ‘cosmetic and personal care’ umbrella, the acceptance limits show in Tables 1 and 2 broadly apply. Testing for microbiological limits
encompasses both qualitative and quantitative assessment of microorganisms already present in the formula upon manufacture. These are quality control tests that may be performed on a routine basis, supporting lot release or product batching. Limits defined in applicable regulatory
references or established from a microbiological quality risk assessment will qualify an upper threshold for contamination, beyond which the product may present a safety risk to consumers. Tests for objectionable organisms have a qualitative outcome: the presence of specified organisms that may pose a risk to an end-user cannot be present in the formulation at any concentration.
Quality testing Microbiological quality testing can be performed in various ways. Typically, culture-based methods are used, meaning determinations are made from microbial recovery observed on solid and liquid media that has been validated for growth-promoting,
www.personalcaremagazine.com ≤1 x 102 CFU per g or mla
Absence in 1 g or 1 ml Absence in 1 g or 1 ml Absence in 1 g or 1 ml Absence in 1 g or 1 ml
Other products ≤1 x 103 CFU per g or mlb
Absence in 1 g or 1 ml Absence in 1 g or 1 ml Absence in 1 g or 1 ml Absence in 1 g or 1 ml
Due to inherent variability of the plate count method, according to USP Chapter 61 or EP Chapter 2.6.12, Interpretation of results, results considered out of limit if
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