It is undeniable that the preservation system is an important part, if not the most important part, in formulations that require it. There are a plethora of cosmetic preservatives and preservative blends available to today’s product development chemist. But with so many options available, how should the formulator select the preservative or preservative blend that would be the most effective in their particular system? In some cases, the options might have already been narrowed by the requirements of the project or the product’s concept. For example, the use of natural preservatives, or the restriction of certain others, might be specified in the development request. If preservation guidelines have not been established, the formulator must consider many factors when deciding on a preservation strategy. A few of these include:
Is the final product water-based or anhydrous? Microbes thrive in water, hence the need to always preserve a water-based product. By definition, an anhydrous product is unlikely to support microbial growth, but in some instances, it might be prudent to include a preservative if the product inadvertently comes into contact with water through humidity, cross-contamination or condensation. A body oil used in the shower is such an example.
Because many preservatives are most effective within a given pH range, the pH of the final product should be adjusted to be compatible with that of the preservative being considered. For some product forms, pH can also determine whether or not a preservative will be required. Bar soaps, for example, are inherently alkaline and typically do not need to be preserved.
Since some cosmetic ingredients, especially surfactants, already contain preservatives, this can be factored into the determination of the overall preservative load.
Intended product use
Will the product be a leave-on or rinse-off?
Will the product be commercialized domestically or internationally as well? If so, the formulator will do well to become familiar with the regulatory requirements of the country in which the product is to be marketed.
Broad Spectrum preservatives, as the name implies, are effective against a broad spectrum of microbes, including bacteria, yeast and mold. They are commonly used, are predominantly synthetic, are represented in different chemical classes, and are often available as blends. Geogard 221 (Dehydroacetic Acid [and] Benzyl Alcohol) and Euxyl PE 9010 (Phenoxyethanol [and] Ethylhexylglycerin) are two such examples.
If a ‘natural preservatives’ claim must be substantiated, then the formulator’s options are significantly narrowed but increasingly expanding. Blends of botanical extracts, organic oils and naturally derived glycols are now becoming widely available.
The following links provide more information on the subject:
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