Microbiological contamination of cosmetics and personal care products during the manufacturing and production process is a common concern in the cosmetic industry. The FDA requires that all cosmetics for consumer use be free of filth as well as void of any putrid or harmful substance that could be damaging to human health. Bacteria are everywhere and can biodegrade (break down or feed on) most consumer products. Biodegradation can either cause the products to spoil or result in chemical changes that may be hazardous to the user.
An aerobic plate count for bacteria will indicate the level of bacteria in a product and can sometimes be used to indicate the quality and spoilage level of a product. Obtaining an estimate of the number of bacteria in a cosmetic product can assist in evaluating the sanitary practices during manufacturing and processing as well as in determining possible sources of contamination.
Bacterial plate counts are recommended to be performed on every batch of product following manufacture. Bacterial counts are conducted by taking a sample of the product and placing it in a suitable neutralizer broth, and then plating dilutions to appropriate bacterial growth agar plates. Those plates are then incubated and analyzed to determine if aerobic bacteria are present in the sample. Talc and powder products are recommended to be tested for anaerobic bacteria as well. If the product is contaminated upon evaluation, further evaluation, and possibly reformulation for better microbial protection, may be necessary before being placed on the market for consumer use. If free of contaminants, then the product can continue on to be tested for preservative efficacy (challenge testing),safety and stability prior to distribution.