Challenge Test | EUROLAB

What Is Challenge Test?

Challenge testing deliberately inoculates the cosmetic product with defined micro-organisms and tracks the viable count over time. If the preservative system works, the count falls markedly at the defined time points. The test shows the product can control microbial growth even if contaminated during manufacture and consumer use.

Purpose of Challenge Test

The purpose is to prove the adequacy of the preservative system and to provide data for the period-after-opening (PAO) and shelf-life claims. It is the core microbiological data required in the Product Information File.

Which Products Is Challenge Test Applied To?

Creams, lotions and emulsions
Shampoos and shower gels
Make-up products
Baby care products
Eye-area products

In Which Sectors Is Challenge Test Used?

CosmeticsChemistryRetailPharmaceuticals

Standards Related to Challenge Test

TS EN ISO 11930 (cosmetics — evaluation of the antimicrobial protection)
TS EN ISO 21149 (enumeration of aerobic mesophilic bacteria)
TS EN ISO 16212 (enumeration of yeast and mould)
TS EN ISO 21148 (general instructions for microbiological examination)
Ph. Eur. 5.1.3 (equivalent approach for pharmaceutical products)

Challenge Test Conditions

Test organisms: Bacteria, yeast and mould strains defined in ISO 11930
Inoculum: Initial micro-organism count defined in the standard
Time points: Enumeration is performed on the days defined in the standard
Temperature: Incubation temperature defined in the standard

Equipment for Challenge Test

Microbiology laboratory and sterile cabinet
Incubators
Autoclave
Colony counting system
Neutraliser preparation setup

Sample Requirements for Challenge Test

Specimen with its market formulation and packaging
Sufficient quantity of specimen; a separate pull for each time point
Formulation and preservative system information must be provided
Packaging type must be provided — an open jar and a pump bottle carry different risk

Duration of Challenge Test

The test runs through the time points defined in the standard and therefore takes weeks. The result cannot be given before the final count point is completed.

Challenge Test Procedure

1The product's neutraliser suitability is verified.
2Test organisms are prepared and their counts determined.
3The product is inoculated with the defined number of micro-organisms.
4It is incubated at the defined temperature.
5Specimens are pulled at the defined time points and viable counts are performed.
6The logarithmic reduction is calculated and compared against the criteria.

Challenge Test Acceptance Criteria

ISO 11930 defines the required logarithmic reduction values by time point in two criteria sets (A and B); criterion A is stricter. The report states which criterion the product meets and, if criterion B, that an additional risk analysis is required. Current values are confirmed from the standard's latest edition.

Evaluation of Results

Neutraliser verification cannot be skipped: if the preservative is not neutralised before enumeration, the result looks better than it really is. Packaging type is also part of the assessment; with an open jar, the user introduces new contamination each time. The test result alone does not establish compliance: (EC) 1223/2009 also requires appointing a responsible person, maintaining a Product Information File, having a qualified person carry out the safety assessment, and notifying the product to the CPNP. Laboratory data feeds into this file.

Challenge Test Report

Product identification, formulation and preservative system
Neutraliser verification results
Test organisms and initial counts
Viable counts for each time point
Logarithmic reduction and criterion met

Accreditation

EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.

Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.

Scope and authorisations

Related Regulations

(EC) 1223/2009 Cosmetic Products Regulation
TS EN ISO 22716 (cosmetics — good manufacturing practices)

Kozmetik Testleri — What Does This Testing Field Cover?

The section below describes the field that the Challenge Test test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.

Cosmetics testing shows that a product stays microbiologically safe throughout its use, delivers the performance it claims and contains no restricted substances. There is NO PRODUCT APPROVAL in this family: no authority approves a cosmetic product; responsibility rests entirely with the manufacturer and with the responsible person established in the EU.

This responsibility model shapes how the field works. Before the product is placed on the market a product information file (PIF) is prepared, a safety assessment (CPSR) is carried out and notification is completed. Inspection comes afterwards and asks for the file; if the file is incomplete the product is withdrawn from the market. Test reports form the evidence base of that file.

On the microbiological side there are two different questions and each is answered by a separate test. The CURRENT microbiological quality of the product is measured by enumeration and testing for specified microorganisms. The EFFECTIVENESS of the preservative system is examined by deliberately inoculating the product with microorganisms (challenge test): can the product resist repeated contamination throughout its use? A jar of cream is touched by a finger at every use; the preservative system must cope with that.

On the performance side, claim substantiation studies are carried out. For sunscreens, determination of SPF and UVA protection and measurement of water resistance are mandatory and are the basis of the value declared on the label. Evidence is also produced by in vivo or in vitro methods for claims such as moisturisation, appearance of wrinkles, hair care and colour retention.

On the chemical side, banned and restricted substances are screened: heavy metals, prohibited colorants, preservative concentrations, UV filter levels and contaminants such as nitrosamines. Products containing nanomaterials carry a separate notification obligation.

The BAN ON ANIMAL TESTING is the most defining constraint of the field. Animal testing cannot be carried out on finished products or ingredients, and a product tested on animals cannot be placed on the market. Alternative in vitro methods (reconstructed human skin models, cell culture based tests) are therefore at the centre of the field, and toxicological assessment rests largely on existing data, read-across approaches and in vitro results.

Stability and packaging compatibility studies determine shelf life and the period after opening (PAO). The interaction of the product with its packaging is also assessed: an active substance may migrate into the packaging, and substances that should not be present may pass from the packaging into the product.

On the process side, good manufacturing practice is demonstrated through ISO 22716; this is separate from product testing but a mandatory part of the file.

Method groups in this field

Microbiological quality
Enumeration of aerobic mesophilic bacteria, yeasts and moulds; testing for Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans and E. coli.
Preservative efficacy
Resistance of the preservative system to repeated contamination by challenge test (ISO 11930).
Sun protection
In vivo SPF determination, in vitro UVA protection determination, water resistance and critical wavelength measurements.
Chemical analysis
Heavy metals, banned and restricted substances, quantification of preservatives and UV filters, contaminant screening.
Safety assessment
In vitro irritation and sensitisation methods, toxicological risk assessment, exposure calculations.
Stability and compatibility
Real-time and accelerated stability, packaging compatibility, PAO determination, sensory and physicochemical monitoring.

Commonly confused in this field

There is NO CE marking on cosmetics; conformity is demonstrated through the PIF, the safety assessment and notification.
The responsible person must be established in the EU; unless the exporter arranges this, the product cannot be placed on the market.
Microbiological quality and preservative efficacy are different tests; a product that comes out clean may still have a weak preservative system.
The animal testing ban covers ingredients too; animal test data generated for another market creates a problem of use.
An SPF claim must be supported by measurement; a formulation change requires a new measurement.
A change of packaging may require the stability and compatibility studies to be repeated.

Which decisions these results support

The product information file and the safety assessment
Verification of the preservative system design
Substantiation of SPF and efficacy claims
Determining shelf life and the period after opening
Compliance with destination market restrictions for export

Related Tests

Frequently Asked Questions About Challenge Test

We make a preservative-free product — is challenge testing needed?

Yes. Even preservative-free products are expected to show microbial risk is controlled, which may come from the formulation's own properties (water activity, pH, alcohol content). The test proves this.

Is it needed for water-free products too?

Microbial growth risk is low in anhydrous products, and ISO 29621 gives guidance on which products can be considered low risk. However, this assessment must be justified and documented in the file; it cannot be assumed away.