Challenge Test for Cosmetic Preservative Effectiveness

Regarding your questions about challenge testing:

1. Where and how to perform a challenge test: You can contact the Department of Medical Sciences (กรมวิทยาศาสตร์การแพทย์) at their one-stop service in Nonthaburi. Alternatively, individuals with a relevant background can perform the test themselves.
2. Self-test methods/kits: It is possible to perform the test yourself if you have the necessary background and equipment. However, sending samples to a testing facility is also an option, and the cost is often not significantly higher than doing it yourself.
3. Sufficiency of using pre-tested preservatives (e.g., Mild Preserved Eco, Thyme Kill): While using preservatives that have undergone challenge testing as ingredients is a good practice, it does not guarantee that your final formula will be adequately preserved. The effectiveness of the preservative system in a finished product depends on the entire formula composition (especially the presence of natural ingredients that can feed microbes), the manufacturing process (cleanliness, use of heat), and other factors. Therefore, a challenge test on the final product is necessary to confirm that the preservative system is effective for your specific formulation and can provide the desired shelf life (e.g., 2-3 years).