USP Challenge Test
USP 51 - Antimicrobial Effectiveness Test
This Preservative Efficacy Test (PET) or Cosmetic challenge test, is essential for assessing the safety of water based cosmetic products. It is most commonly used for products sold in the United States, but is recognised worldwide.
Buy USP tests
EP, USP or ISO?
PET test details
United States Pharmacopeia (USP)
United States Pharmacopeia - USP 51
Which USP Test?
How Long?
Test Procedure
EP, USP or ISO standard PET test?
The challenge test protocol that you require is governed by the market that you intend to sell your products into.
The EP test method for Europe / UK and the USP method for the USA are well established protocols, offering formulators confidence that their products are robustly protected. The methods are also accepted in many other territories.
The ISO 11930 method has been introduced more recently. Although it is considered a less stringent test than the EP or USP, unlike these Pharmacopoeia test methods, ISO 11930 was designed specifically with cosmetics in mind.
| EP | USP | ISO | |
|---|---|---|---|
| Incubation (days) | 28 | 28 | 28 |
| Sample required (g) | 250 | 250 | 250 |
| Total Species | 4/5 | 5 | 5 |
| Staphylococcus aureus | ● | ● | ● |
| Pseudomonas aeruginosa | ● | ● | ● |
| Candida albicans | ● | ● | ● |
| Aspergillus brasiliensis | ● | ● | ● |
| Escherichia coli | ○ | ● | ● |
PET test details
The major differences between the methods are noted in the table opposite. For oral care products, testing against Escherichia coli is an additional requirement of the EP method. The cost of a cosmetic challenge test varies by the type chosen.
The ISO 11930:2019 method uses less stringent pass criteria compared to the pharmacopoeia methods.
United States Pharmacopeia (USP)
'USP 51 - Antimicrobial Effectiveness Test'
Sometimes referred to as USP 51 or 'USP Challenge test'
It is a Preservative Efficacy Test (PET) that is adapted to cosmetic products to ensure they are safe for consumers in the United States.