Challenge Testing cosmetics, usp 51 challenge test, iso 11930, Vegan Cosmetic Challenge tests, Cosmetics Preservative Efficacy Challenge Testing

Cosmetic Challenge Test

EU No1223/2009 states that cosmetics & personal care products should demonstrate preservation efficacy, as cosmetic preservative systems should ensure product robustness and consumer safety throughout product life cycles. Preservative Efficacy Testing (PET) also known as Challenge Testing is the appropriate tool to substantiate antimicrobial preservation efficacy against microbial contamination. At QACS, The Challenge Test Laboratory, we apply several challenge test protocols.

Cosmetic Challenge Testing methodology may follow Pharmacopoeias, International Standards, Industry or in house developed protocols. QACS is ISO17025 accredited to perform cosmetic challenge testing.

Usp 51 challenge test inoculates 5 microorganisms (Pseudomonas aeruginosa, Staphylococcus aureus, E. coli, Candida albicans, Aspergillus brasiliensis). For usp 51 challenge test we store the inoculated preparation at a prescribed temperature then withdraw samples from the container at specified time intervals and count the organisms.  Minimum sample quantity is 100g and results are available within 35 days.

ISO 11930 challenge test, a reference method to evaluate the preservation of a cosmetic formulation inoculates 5 microorganisms (Pseudomonas aeruginosa, Staphylococcus aureus, E. coli, Candida albicans, Aspergilus brasiliensi). Surviving micro-organisms that remain are measured at defined time intervals within a 28 day period.  Minimum sample quantity is 100g and results are available within 35 days.

Similar to the EP reference standard, the re-inoculation challenge protocol, re-inoculates samples on the 7th day.  The tests is prolonged by 7 days and observations are repeated following the times prescribed.  Minimum sample quantity is 100g and results are available within 42 days.

The multi strain in-house mixed culture test is designed to simulate single inoculation followed by a storage period. We divide several standard strains into categories of bacteria, yeasts and molds & challenge the preparation with a mixture of strains. Readings are reported per strain. Results are available within 42 days. Minimum sample quantity 100g.

Cosmetic Challenge testing involves separately contaminating wet-wipe sub-samples with each one of 5 reconstituted strains. We then test individual sub-samples for microbial count at every interval (0 time, 2 days, 7 days, 14 days, 28 days) and assess log-reduction. The rest of the test complies with the EP reference standard. Results are available within 35 days. Minimum sample quantity 100g.

QACS Lab has replaced all animal-by products with a selection of plant-based ingredients and developed vegan challenge tests for cosmetics. Vegan Cosmetic Challenge tests meet legislation requirements without compromising vegan ethics. Growth properties of plant-based media are directly comparable with the growth properties of the traditional media, allowing the optimal growth of a wide range of microorganisms.

Synergistic effect occurs, when the combined interaction of two or more compounds produces a combined effect greater than the sum of their separate effects.

The test is particularly targeted for preservation systems in the presence of boosters, added to limit the amount of preservative concentration and to ensure higher antimicrobial protection. Due to synergistic effect, when added together, the expected activity of components rises significantly. The evaluation of the synergistic effect is recommended to ensure effective preservation in mild cosmetic formulations. Besides the optimized preservative content, manufacturers benefit from reduced formulation costs as smaller amounts of preservatives are being used.

At QACS, we perform Challenge test ISO 11930accredited under ISO 17025. Based on the results, we evaluate the range of synergistic effect for each preservative combination and conclude on synergism or antagonism of the particular of preservatives mix.


QACS, Challenge Testing services assist cosmetic RnD decisions with:

→ Competitive market prices

→ Real-time reporting

→ Intermediate results at specific time intervals

→ option for urgent delivery reporting at 14 days

→ EU carriage policy

→ 24h courier service for sample collection

If you need your test results urgently, we can perform a fast screening process within 14 days.