USP 51 – Antimicrobial Effectiveness Testing

USP 51 is an antimicrobial test method that determines the antimicrobial efficacy of a material’s antimicrobial preservatives. Similar to other preservation challenge methods, USP 51 is commonly used to evaluate the performance of preservatives used in cosmetics and personal care products.

The USP 51 antimicrobial test is from chapter 51 of the United States Pharmacopeia. It is often referred to as a bioburden test.

Standard testing is tested against 5 organisms, 3 bacteria: Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, as well as 1 fungus: Aspergillus niger, and 1 yeast: Candida albicans. Testing is performed for a minimum of 28 days.

Preservatives are antimicrobial additives that are incorporated into product formulations to help maintain the quality of a product by inhibiting and reducing microbial contamination.

Preservatives can be inherently toxic; knowing the correct dose that efficiently inhibits microbial growth but does not have adverse effects on human health is key to a successful product formulation.

Customers commonly request USP 51 for personal care products, pet care products, and cosmetics.  USP 51 is also often used for product development testing, quality control and product performance testing.

Customers also request other preservation methods including ASTM E640 for water containing cosmetics and personal care products.

For more information on preservation testing and antimicrobial performance, contact our antimicrobial testing laboratory at 847-483-9950 or