The cosmetics industry is evolving rapidly, and traditional challenge testing methods are struggling to meet the new demands. Historically, most cosmetic products were water-based and relied on standard preservatives, making safety testing relatively straightforward. 

Today, formulations are increasingly complex. Recent innovations, such as probiotic skincare, waterless formats, and made-in-store cosmetics, are introducing new risks and outpacing existing regulatory guidance. These shifts have implications not only for finished formulations but for new product development (NPD) too.

ISO 29621 offers a solid foundation for assessing microbial risk but it’s not enough on its own. Brands need to adopt evidence-led, risk-based approaches tailored to their specific formulations and reflective of real-world use, not just lab conditions. Failure to do so may result in product recalls, financial loss, and significant brand damage, including a breakdown in consumer trust.

With manufacturing lines being moved into stores and over 150 product variants offered from just 10 core ingredients, microbial safety is no longer a one-size-fits-all equation. Add to that probiotic formulas, which introduce intentional microorganisms, and the rise of sustainable “just add water” products – technically exempt from challenge testing since they are anhydrous, but where rehydration introduces risk – and the cracks in existing testing protocols are clear.

Relying solely on outdated standards leaves gaps that brands can’t afford to ignore. ISO 29621 offers a smarter, risk-based framework, but it’s only effective when paired with expert oversight and real-world evidence.

At MSL, we help brands tailor testing plans, navigate emerging formats, and stay ahead of evolving regulatory expectations.  Our advice is to take a proactive, evidence-led approach to microbial safety that:

• Reassesses product risk using ISO 29621 as a strategic foundation.
• Avoids blanket testing protocols that overlook formulation nuance.
• Ensures testing reflects how products are actually used, not just how they perform in controlled lab conditions. 

To discuss your testing needs or find out more, please contact us.