When you open a jar of face cream or use a bottle of shampoo the first thing you think of is probably might not be the invisible world of microbes. But as a cosmetic chemist, I think about it all the time. That’s because cosmetics, especially those that contain water, can be a breeding ground for bacteria, yeast, and mold. To keep products safe and stable, we use preservatives.
Preservative systems are designed to prevent microbial growth during a product’s shelf life and through reasonable, expected use by the consumer especially after it’s been opened and exposed to the air and applicators which can include our fingers. Common preservatives today include benzyl alcohol, phenoxyethanol, and sodium benzoate.
A combination of preservatives is generally necessary because the susceptibility of microbes varies. Each preservative has its own strengths and limitations. Choosing the right preservative package depends on several factors including:
- Product type – Each product type has unique aspect to consider examples include lotions, makeup which is applied in the eye area, and clay face masks
- pH level – Some preservatives only work in certain pH ranges
- Packaging – Product in a pump bottle is less exposed to air and the consumer’s fingers than a wide-mouth jar.
- Target market – Regulations can affect the choice of preservatives and as well as consumer and retailers have preferences.
But even the best preservatives can fail if we don’t pay attention to manufacturing hygiene. If a product is made in an unclean environment with dirty equipment or contaminated water it can already harbor significant levels of bacteria or mold before it’s even packaged. In this case, even a strong preservative system that had demonstrated efficacy in the lab might not be able to stop those microbes from growing.
Manufacturing hygiene refers to cleanliness and sanitation practices used during the production of cosmetics. This includes, but is not limited to, cleaning and sanitizing equipment, controlling air and water quality, packaging cleanliness, as well as personnel hygiene and utilization of protective gear. Environmental monitoring is also a crucial aspect of manufacturing hygiene. This regular testing of surfaces, air, and water systems helps to catch problems before they can affect products.
Preservatives are not a substitute for proper manufacturing hygiene. They are like a seatbelt, there for your safety but you still need to operate your car carefully. In cosmetic science, that means combining clean manufacturing practices with a well-designed preservative system to produce products that are both safe and effective.
