Samples are prepared with preservative, and inoculated separately with strains of bacteria and fungi which may occur under normal customer use conditions, including Gram-positive and Gram-negative bacteria, mold and yeast. Our aim is to test whether your product is safe to use without risk of contamination for the full product life once it is opened. SGS challenge tests can be carried out on the full range of cosmetic products, and it is advisable to conduct tests as early as possible in product development.