Microbiological tests for cosmetic products: The ISO 17516 guideline and Nano-Test solutions
Cosmetic products offer an extremely favorable breeding ground for the growth of microorganisms due to their water, oil, protein, and other nutrient content. If a cream, lotion, or shampoo becomes contaminated with bacteria, yeasts, and molds on its way from production to the consumer, this can lead to product spoilage, unpleasant odors, as well as changes in color and consistency. Even more importantly, a contaminated cosmetic product can cause skin infections, allergic reactions, and even serious systemic diseases. To exclude these risks, microbiological tests for cosmetics are of great importance.
The Cosmetics Regulation of the European Union (EC) No. 1223/2009 and the Cosmetics Regulation in force in Turkey stipulate that cosmetic products must be microbiologically safe. The fundamental international standard to which these requirements are aligned is ISO 17516. This standard sets the maximum permissible microbial counts in cosmetic products as well as the pathogens that must not be present under any circumstances.
ISO 17516 standard: Permissible microbiological limit values
ISO 17516 establishes quantitative and qualitative criteria for assessing the microbiological quality of cosmetic finished products. This standard provides different limit values depending on the intended use of the product and the target group. In particular, significantly stricter limit values apply to products that come into contact with the skin of infants, the eye area, and mucous membranes.
Microbiological acceptance criteria according to ISO 17516
The following table summarizes the permissible limit values for microorganisms in cosmetic products:
| Microorganism | Products for infants, the eye area, and mucous membranes | Other cosmetic products |
|---|---|---|
| Total number of aerobic mesophilic bacteria | ≤ 1 × 10² CFU/g or ml | ≤ 1 × 10³ CFU/g or ml |
| Total number of yeasts and molds | ≤ 1 × 10² CFU/g or ml | ≤ 1 × 10³ CFU/g or ml |
| Escherichia coli | Must not be present | Must not be present |
| Pseudomonas aeruginosa | Must not be present | Must not be present |
| Staphylococcus aureus | Must not be present | Must not be present |
| Candida albicans | Must not be present | Must not be present |
Basic Test Categories in Cosmetic Microbiology
In order to comprehensively evaluate the microbiological safety of a cosmetic product, different test categories must be carried out in combination. These tests include both the control of the raw materials and the end products.
1. Quantitative Counting Tests
These are counting tests to determine the general microbial load of the product. These tests are an indicator of the production hygiene and the effectiveness of the preservation system.
2. Tests to detect pathogens
These are tests for the detection of pathogens, which, according to ISO 17516, must not appear in the product under any circumstances. These tests are based on the principle of enrichment and isolation on selective culture media.
- ISO 21150: Detection of Escherichia coli.
- ISO 22717: Detection of Pseudomona aeruginosa.
- ISO 22718: Detection of Staphylococcus aureus.
- ISO 18416: Detection of Candida albicans.
- ISO 18415: General guidelines for the detection of specified and non-specified microorganisms.
3. Efficacy Test (Challenge Test)
This test assesses how resistant the product's preservation system is to microbial contamination that may occur during manufacture or when used by the consumer. The product is inoculated with certain microorganism strains and the decrease in microorganism count is monitored at certain intervals (0, 7, 14, 28 days).
- ISO 11930: Assessment of the antimicrobial preservative effectiveness of cosmetic products.
- USP <51>: Preservative effectiveness test according to the United States Pharmacopeia.
The Challenge test is particularly important for water-based formulations (cream, lotion, gel, shampoo). As a result of the test, the product is classified in category A, B or C; where A is the highest preservative efficacy and C means the lowest efficacy.
Fast microbiological detection methods
Even if traditional culture methods continue to represent the gold standard, the need for quick results has led to the development of alternative technologies. In particular, the ATP bioluminescence method proves to be a promising tool for the rapid detection of microbial contamination in cosmetic products.
Comparative studies have shown that ATP-based tests have a high correlation with the standard plate counting methods. This method offers, especially in situations where quick decisions have to be made in the production line (e.g. in advance screenings before batch release), time and cost advantages. However, in order to be recognized by the supervisory authorities as a final result, it must be validated by standard cultural procedures.
Accredited Microbiological Test Services for Cosmetics with Nano Test
The microbiological safety of your cosmetic products is crucial for consumer health as well as the reputation of your brand. Nano-Test is a reliable partner of the cosmetics industry with its comprehensive microbiological testing services in ISO/IEC 17025-accredited laboratories.
Nano-Test – Performance Description
Nano-Test offers microbiological testing services for cosmetic products that are fully compliant with ISO 17516 and the corresponding ISO standards. Our service portfolio:
- Quantitative determination: Determination of the total microbial count according to ISO 21149 (aerobic bacteria) and ISO 16212 (yeasts and molds).
- Detection of pathogens: Detection of E. coli, P. aeruginosa, S. aureus, and C. albicans according to the standards ISO 21150, ISO 22717, ISO 22718, and ISO 18416.
- Effectiveness test (Challenge test): Tests to assess the effectiveness of the product's preservative system according to ISO 11930 and USP <51>.
- Method conformity tests: Assessment of the suitability of neutralizers, diluents, and culture media specifically for your product matrix.
- Hygiene monitoring: Monitoring the risk of cross-contamination using samples from the production environment (surfaces, air, personnel).
- Rapid screening: Pre-screening and time-saving solutions with alternative methods such as ATP bioluminescence.
All our analyses are presented as GLP-compliant reports that have a test approval and ensure data integrity (ALCOA+ principles). Our goal is to ensure the acceptance of your products in global markets while guaranteeing consumer safety at the highest level.
The advantages of nano-test in cosmetic microbiology:
- Accredited infrastructure: Internationally recognized test reports with ISO/IEC 17025 accreditation.
- Current compliance with standards: Immediate adaptation to current changes such as the revision of ISO 17516.
- Quick results: Reporting within 5–7 working days for standard microbiological tests.
- One-stop solution: All microbial counts, pathogen detections, and challenge tests under one roof.
- Expert team: A team with experience in microbiology and cosmetics law.
Microbiological tests on cosmetic products are not only a legal obligation, but also an indispensable quality assurance tool to protect consumer safety and brand reputation. Tests in accordance with ISO 17516 standards ensure the acceptance and reliability of your product on international markets.
With its accredited laboratory infrastructure, its team of specialist microbiologists and its GLP-compliant processes, Nano-Test fully meets the requirements of cosmetic manufacturers for microbiological tests. Collaborate with Nano-Test to increase the safety of your products and accelerate their market launch.