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ISO 21149 Cosmetic Microbial Testing (Aerobic Mesophilic Bacteria Enumeration)
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Summary
ISO 21149 is an internationally recognized test standard used to evaluate the microbiological quality of cosmetic products by detecting the presence of aerobic mesophilic bacteria. The test assesses total contamination of bacteria using three different culture-based methods. The results are reported as Colony-forming units (CFU/g or CFU/ml). ISO 21149 is widely recognized and accepted by regulatory authorities globally as scientific evidence for validating microbiological quality of cosmetics and it helps manufacturers ensure product hygiene, safety and manufacturing quality control.
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Quick understanding of the test
ISO 21149:2017 - Standard Method for Detecting Aerobic Mesophilic Bacteria in Cosmetics
- Ensures consumer safety by identifying harmful bacteria.
- Helps avoid costly product recalls due to contamination.
Turnaround Time
Passing criteria
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What is ISO 21149?
ISO 21149:2017 is an international test standard that evaluates the microbiological quality of cosmetic products, by enumerating and detecting aerobic mesophilic bacteria.
ISO 21149 provides standard framework for both quantitative and qualitative assessment. Quantitative evaluation determines the level of bacterial contamination, and qualitative assessment verifies the presence or absence of microorganisms, providing manufacturers and regulatory bodies with reliable information on product safety.
Scope of ISO 21149 in cosmetic microbiology
ISO 21149 has a broad application. It applies to cosmetic products including:
- Creams and lotions (oil-in-water or water-in-oil emulsions)
- Shampoos and conditioners
- Liquid soaps and shower gels
- Make-up and skincare products
- Raw materials used in cosmetic production
While this standard is applicable to a wide range of cosmetic products, alternative methods may be required for testing certain water-immiscible formulations.
ISO 21149 test methods overview
ISO 21149 uses multiple validated techniques for microbial enumeration, depending on product type
- Plate count method
- Membrane filtration
- Enrichment method
ISO 21149 test procedure step by step
1. Plate count method
Plates preparation – Pour plates or spread plates are prepared by using a specified culture medium.
Inoculation – The plates are inoculated with a known quantity of initial suspension.
Incubation – The inoculated plates are incubated aerobically at 32.5°C ± 2.5°C for 72 ± 6 hours.
Colony counting – After the incubation period, the number of colony-forming units (CFU) is counted and the number of aerobic mesophilic bacteria per ml per gram of the cosmetic product is calculated.
2. Membrane filtration method test
Sample preparation – A defined amount of sample is filtered through a membrane filter and washed in a filtration apparatus containing a small amount of suitable sterile diluent.
Membrane transfer on agar plates – The membrane filter is then transferred onto an agar plate and incubated at 32.5°C ± 2.5°C for 72 ± 6 hours
Colony counting – After incubation, the number of colony-forming units (CFU) is counted and the number of aerobic mesophilic bacteria per millilitre or per gram of the cosmetic product is calculated.
3. Enrichment Method (Detection of aerobic mesophilic bacteria by enrichment broth)
Sample preparation- 1g or 1 ml of cosmetic test sample is added to the enrichment broth to prepare the initial suspension.
Inoculation – A defined amount of the sample preparation is inoculated in a non-selective liquid medium containing appropriate neutralizers and/or dispersing agents.
Incubation – The sample mixture is then incubated at 32.5°C ± 2.5°C for at least 20 hours.
Subculturing on agar medium – After incubation, an aliquot of the previously inoculated liquid medium is transferred to a non-selective solid agar medium.
Incubation – The plates are subjected to aerobic incubation at 32.5°C ± 2.5°C for 48 to 72 hours.
Microbes detection/ results – The plates are observed for any bacterial colonies and the results are expressed as the “presence or absence” of aerobic mesophilic bacteria per sample of the cosmetic product.
Understanding ISO 21149 results
ISO 21149 testing results help to determine
- Whether microbial levels are within acceptable limits
- Product hygiene and manufacturing quality
- Risk of contamination during storage or use
Higher CFU counts may indicate:
- Poor raw material quality
- Inadequate preservation system
- Contamination during production
ISO 22149 vs Other standards
Parameter | ISO 21149 – Aerobic Mesophilic Bacteria | ISO 16212 – Yeast & Mould | USP <61> Microbial Enumeration |
Purpose | Quantitative assessment of aerobic mesophilic bacteria. | Quantitative evaluation of yeasts and molds in cosmetic products. | Quantitative microbial enumeration of non‑sterile products : Total Aerobic Microbial Count (TAMC) and Total Yeast & Mold Count (TYMC). |
Identified microorganisms | Aerobic mesophilic bacteria. | Yeasts and moulds | Aerobic bacteria + yeasts and moulds (counts reported separately) |
Method types | Plate counts (agar), membrane filtration, enrichment for presence/absence | Plate count and membrane filtration for yeast/mould | Plate count (pour/spread), membrane filtration, and MPN methods; includes method suitability/neutralization |
Result interpretation | CFU per gram or millilitre or presence/absence | CFU per gram or millilitre | CFU per gram or millilitre for TAMC and TYMC |
Scope of products | Cosmetic products where bacterial contamination is a concern | Cosmetic formulations prone to yeast/mould contamination (creams, emulsions) | Non‑sterile products including cosmetics, personal care, pharma |
Use case | Cosmetic microbiological quality & compliance (bacterial contamination) | Cosmetic safety testing for fungal contamination | Broader quality control (manufacturing release, regulatory compliance) |
Regulatory relevance of ISO 21149
ISO 21149 plays an important role in demonstrating cosmetic product safety and regulatory compliance worldwide. Manufacturers are legally required to ensure that the products are safe and free from harmful microbial contamination.ISO 21149 is a harmonized international testing methodology that supports cosmetic product safety reports (CPSR). It is widely referenced under EU cosmetic regulation in European markets and globally for cosmetics safety assessments.
Turnaround time
The typical turnaround time for ISO 21149 is 3-4 weeks.
Why is ISO 21149 important for cosmetics?
- Consumer safety – ISO 21149 identifies the aerobic mesophilic bacteria that cause infections and irritation to skin, eyes and mucous membranes.
- Product quality – Regular microbiological testing ensures cosmetic products are safe,high-quality and market-ready
- Regulatory compliance – Testing in accordance with ISO 21149 helps manufacturers meet legal requirements and ensures compliance with safety standards.
- Process monitoring – This testing enables early detection of microbial contamination during production, allowing manufacturers to implement corrective measures and improve production processes to maintain product safety and quality.
Common causes for microbial contamination in cosmetics
Cosmetic products can become contaminated at multiple stages of their lifecycle. The pathway can be:
- Contaminated raw materials or water – Microorganisms enter formulations through improperly controlled ingredients or non-purified water systems.
- Poor manufacturing hygiene – Inadequate sanitation of equipment, filling lines or production environments allows microbial transfer into finished products.
- Ineffective preservation systems – formulations with faulty/insufficient preservative efficacy enable microbial growth during storage or consumer use.
- Packaging and storage conditions – Improper packaging or environmental exposure (humidity, temperature) can promote microbial proliferation
- Consumer use contamination – Repeated exposure to fingers, water ingress or improper closure can introduce microorganisms after opening the product.
Why choose MIS for ISO 21149 testing?
At Microbe Investigations Switzerland (MIS), we provide ISO 21149 testing services that help cosmetic manufacturers ensure their products meet the highest standards of microbiological safety.
Alongside this test, MIS also offers related services including ISO 16212, USP 61, ISO 11930, ISO 18415, and custom microbial risk assessments tailored to your unique product formulations.
Our expert microbiologists work closely with your team to identify the most relevant tests for your product type, intended use, and market requirements — ensuring full compliance with regulatory standards.
Request ISO 21149 testing
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Frequently Asked Questions
DR. Martinoz Scholtz
The test specifies methods for the enumeration and detection of mesophilic aerobic bacteria present in cosmetic products using plate count, membrane filtration or enrichment broth methods.
The test applies to cosmetics, beauty products and personal care products that are prone to microbial contamination by aerobic bacteria.
The test takes 4 weeks to complete.
The standard outlines the methods for detecting and enumerating aerobic mesophilic bacteria in cosmetic products.
Microbial contamination is detected either by counting colonies on an agar plate after incubation or by using an enrichment broth method for detecting low levels of bacteria.
Regular testing throughout the product life cycle, including during the development, manufacturing and shelf-life phases, is generally recommended.
ISO 21149 tests for the presence of bacteria while ISO 16212 tests for the presence of yeast and mold.
Yes, the standard can be used to test raw materials too.
Aerobic mesophilic bacteria grow in the presence of oxygen at temperatures between 20–45 °C. In cosmetics, they are the indicator of bacterial contamination.
Acceptance criteria depends on product type and regional regulatory requirements.
Microbial testing ensures cosmetic products are safe for consumer use and free from harmful contamination. It verifies manufacturing hygiene, preservative effectiveness, and product stability throughout shelf life.
ISO 21149 measures the total count of aerobic bacteria present in a cosmetic product. ISO 11930 evaluates the effectiveness of preservatives by intentionally challenging the product with microorganisms. So, ISO 21149 checks contamination levels while ISO 11930 assesses preservation performance to prevent microbial growth.
Bacteria are counted using culture-based methods. The sample is plated on agar, incubated under controlled conditions. Post incubation, the visible bacterial colonies are counted and reported as colony-forming units (CFU/g ot CFU/ml)
ISO 21149 primarily measures total aerobic bacterial load instead of identifying specific pathogens. However, other ISO methods such as ISO 22718 and ISO 18416 are used to detect specific pathogens such as Staphylococcus aureus or Candida albicans.
Microbial growth depends on water activity, pH, nutrient availability, preservative systems, temperature and other storage conditions.
ISO 21149 is not mandatory, but widely referred to and accepted as a standard for validating microbiological quality of cosmetic products.
Regular testing throughout the product life cycle, including during the development, manufacturing and shelf-life phases, is generally recommended.
Failure indicates microbial contamination above the standard limits. The raw materials, processing hygiene and preservative systems, testing conditions are checked and retests are performed.
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