Comparatively Speaking: Cosmetic Preservatives

By: Anthony J. O'Lenick, Jr., Siltech, LLC

Posted: April 20, 2010

To serve the novice cosmetic chemist and/or to refresh the seasoned formulator, Tony O’Lenick asks Perry Romanowski: Why is cosmetic preservation necessary, and why are preservatives vilified?¹

There are two primary reasons preservatives are needed:
1. To stop microbes from spoiling products; and 
2. To stop microbes from causing disease.

The microbes that can infect formulas primarily include bacteria, mold and yeast. In small quantities, they do not pose much of a problem, but when they multiply, look out. Bacteria like Pseudomonas can cause all kinds of health problems including skin and eye infections, toxic shock, strep throat and even food poisoning. Yeast like Candida albicans can cause thrush, and many other bacteria can cause products to smell awful, change color or otherwise break down. (This is what stability testing is for.)

Following is a list of common preservatives used in cosmetic and personal care products. As future (or current) formulators, readers will undoubtedly be using many of them.

Parabens
Parabens are the most commonly used preservatives. They are derivatives of p-hydroxybenzoic acid and include methylparaben, propylparaben and butylparaben. They are typically supplied as powders and can sometimes be difficult to incorporate into a system due to water solubility limitations. They are effective against a broad spectrum of bacteria and fungi. They do have pH limitations and are not effective against all microbes so formulators will usually need an additional preservative.