Preservative Efficacy Testing of Aqueous Cosmetics and Drugs without Counting Colonies

Preservative efficacy testing or "challenge testing" is performed on aqueous cosmetic and drug products to determine the minimum effective concentration of antimicrobial preservatives required for adequate preservation. Products are satisfactorily preserved if they meet appropriate acceptance criteria. Methods of preservative efficacy testing include: compendial methods, such as the United States Pharmacopoeia (USP) and the European PHarmacopoeia (EP) methods; trade association methods, such as the Cosmetic, Toiletry & Fragrance Association (CTFA) method; and rapid procedures, such as the linear regression method.^1-4