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Cosmetics PET – Technical Information

Test: Preservative Efficacy Test

Also known as: PET, Challenge test, Preservative test


For most products this test is a requirement of the Cosmetics Regulations.  It determines whether the preservative system in your product works by adding large numbers of organisms and assessing how quickly they are reduced.  This test only needs to be carried out once for each product formulation.

Which method?

We would recommend using the ISO 11930:2012 method for new cosmetic products as the test is aimed specifically at this type of product.  It takes into account that cosmetic products may be used every day by the customer and that over exposure to high levels of preservatives is undesirable.  This is balanced with the need to minimise the risk to the customer of products spoiling.

The other widely used test is that of the European Pharmacopoeia (EP).  This test has long been used in the cosmetics industry as there simply was no other method available.

Both tests satisfy the requirements of the Cosmetics Regulations.

MCS Test Reference:

TMMCS22 (ISO 11930 method)    TMPh1(EP method)

Quantity of test sample required: 150 g

Total Test Time: 35 days

Test Organisms Used:

S. aureus, Ps. aeruginosa, E. coli, C. albicans and A. brasiliensis


Sending Samples:

Samples must arrive by 4pm on the Tuesday of each week to guarantee that they will go on test that week.

Send samples to the address at the bottom of this page accompanied by a Test Request Form.  Samples do not have to be in finished packaging, clean sample containers are suitable.


Written reports are issued on completion of the test.  Full results with the recovery of each organisms at each time point will be given along with a Pass/Fail result.  Early warnings will be given if the product fails to meet any test criteria at earlier time points.