The purpose of the preservation challenge test is to confirm that the cosmetic product, when used as intended, prevents microbial growth and is thus microbiologically stable. However, it should be noted that preservation challenge tests are merely models and do not guarantee 100% safety.
The execution of a preservation challenge test is required by the EU Cosmetics Regulation as part of the safety assessment (see Annex I, Point 3 of the Regulation).
Exempt from the requirement to conduct a preservation challenge test are products that meet one or more of the following conditions.

• pH value: <3
• pH value: >10
• water-free products
• alcohol content: >20%
• filling temperature: >65°C
• water activity: <0.75
• solvent-based products
• oxidizing products
• aluminum chlorohydrate content: >25%

Other low-risk products may be identified as part of an individual risk assessment.