Microbiological Limits in Cosmetics

Abstract

Cosmetics are non-sterile products which can be contaminated with microorganisms in limit numbers and types. If the numbers of microorganisms are excess, the microbes may grow by using ingredients in the products causing physicochemical changes and finally loss in product stability and activity. Excessive microbial contamination is a major problem in cosmetic industry. Standard requirements of United States Pharmacopeia (USP) edition 42, International Organization for Standardization (ISO) 17516: 2014[E] and Thai Herbal Pharmacopoeia (THP) 2019 for microbiological investigations in non-sterile products are quite similar in quantitative and qualitative aspects. However, the names of the test method and test focus are different. The requirement of USP concentrates on “non-sterile products for skin” and “Microbial Enumeration Tests” are the method names, while ISO 17516: 2014[E] uses the method name “Microbiological Limits” and focuses on “cosmetics”.  The requirement of THP emphasizes on “non-sterile pharmaceutical products with and without herbs for intact skin” and “Microbial Limit Tests” are the test names. In quantitative aspect, USP requirements for total aerobic microbial count (TAMC) and total combined yeasts and molds count (TYMC) are ≤ 1 x 10² and ≤ 1 x 10¹ colony forming unit (CFU)/g or ml of product, respectively. The maximum acceptable count is 2-fold which make the numbers are equal to those of the THP (TAMC and TYMC ≤ 2 x 10² and ≤ 2 x 10¹ CFU/g or ml of product, respectively). Consequently, the requirements of USP and THP are more strict than that of ISO 17516: 2014[E] which combines TAMC and TYMC into ≤ 1 x 10³ CFU/g or ml of product. In qualitative aspect, ISO 18415: 2017[E], USP and THP requirements for undesirable specific microorganisms are Pseudomonas aeruginosa and Staphylococus aureus. Additionally, ISO requires more undesirable microorganisms which are Candida albicans  and Escherichia coli. The cosmetic requirement for microbiology in an announcement B.E. 2559 of the Ministry of Public Health harmonizes with the aforementioned Pharmacopoeias and ISO except Clostridium spp. is an undesirably added microorganism in products with herb. The methods of microbial enumerations and specific microorganism determinations are different in each standard. This article will focus on the methods of ISO requirement. The evaluations of cosmetic products in microbiological stability and risk are the quality assurances, especially products with low microbiological risk and safe for users would increase the product quality and decrease the necessity in microbial investigation in cosmetics.