The cosmetic challenge test, also known as the preservative efficacy test (PET), is an important part of the product information file. According to EU Regulation 1223/2009, every cosmetics manufacturer must ensure that the product is microbiologically stable during the declared shelf life.
Basically, the challenge test checks the effectiveness of cosmetic product preservatives and whether it is able to withstand various types of (challenge) contamination during production, from the environment and from direct contact with the human body to which the cosmetic product is exposed. The Challenge test checks the efficiency of the canning system, using the international standard ISO 11930: 2019.
The test is based on monitoring the presence of various pathogens in the cosmetic product.
● Staphylococcus aureus (gram-positive bacterium)
● Pseudomonas aeruginosa (gram-negative bacterium)
● Candida albicans (fungus)
● Escherichia coli (gram-negative bacteria)
● Aspergillus brasiliensis (fungus) The residual concentration of these microorganisms is then determined after 7, 14 and 28 days. A product is considered to have passed the preservative efficacy test if fungal concentrations do not increase during the testing period and if bacterial concentrations are sufficiently reduced by day 14 and do not increase from that time until the end of the test. Challenge test is not required for certain types of cosmetic products. Microbiological low-risk products can be exempted from the preservative efficacy test, because, due to the characteristics of the product, the probability of microbiological contamination for such products is very small or even non-existent. Product characteristics that define products as microbiologically low-risk products are described in ISO 29621: 2017. These characteristics are as follows:
● Water activity in the formulation: water-free products
● pH of the formulation: highly acidic (pH below 3) or highly alkaline (pH above 10) products
● Alcohol content: products with more than 20% alcohol concentration
● Formulation with raw materials that can create a hostile environment: such as strong oxidants, polar organic solvents, oxidative dyes, aluminum- and related salts or propellants.
● Production conditions: if the containers are filled at a temperature higher than 65 degrees Celsius
● Types of packaging: product packed in pressurized containers, dosing pumps or single dose units
● A combination of the above factors