Preservative Effectiveness / Challenge Testing

Preservative Effectiveness Testing (PET), also known as challenge testing, evaluates how well a cosmetic or personal care product’s preservative system controls microbial growth over time. The finished product is deliberately inoculated with a standardized panel of bacteria, yeast, and mold, and the reduction of these microorganisms is measured at defined intervals. This testing is performed in accordance with recognized industry standards such as USP <51> and ISO 11930.

PET is a critical safety requirement for water-containing formulations including lotions, creams, cleansers, serums, and other aqueous cosmetics. Results are used to support Cosmetic Product Safety Reports (CPSR), MoCRA compliance, retailer requirements, shelf-life determination, and product launch approval. Products with low water activity may be considered low risk and not subject to PET; however, water activity testing is recommended to document exemption eligibility.