In the old days of formulating if you had a microbial problem you could simply put in parabens and formaldehyde donor ingredients and that would be effective most of the time. If you had a particularly persistent problem you could also include something like Kathon. As a natural formulator those ingredients are generally frowned on and not allowed. This means you’ll need some alternative cosmetic preservatives.
While hurdle technology will help, it is not usually enough to preserve your products. You still need a preservative. If you don’t want to use standard products here are some options.
Phenoxyethanol – This ingredient is not approved by COSMOS but it is a common preservative for natural formulators. It is a solvent for fragrances and has a light rose odor. It is effective against some bacteria and fungi. Also good against pseudomonas. It has a wide pH range and is effective from pH 3 – 10.
Phenethyl Alcohol – This ingredient is approved by COSMOS and works similarly to phenoxyethanol. It has a stronger odor however.
Organic acids and their salts – There are a wide range of organic acids that are effective as preservatives. These include
These ingredients are mostly approved by the COSMOS standard and are effective against fungi and to some extent bacteria. They only work at lower pH however so if you use them you need to formulate below pH 5.0
Benzyl Alcohol – This material is effective against a broad spectrum of microbes. While it can be found in nature most of the benzyl alcohol used commercially is synthetically produced. One drawback is that it is a known allergen. There are also some compatibility issues with benzyl alcohol and nonionic surfactants.
Natural preservative boosters
Less effective ingredients that can help boost the efficacy of alternative preservatives include
The following ingredients can help disrupt growth by interfering with the microbial cell membranes.
- Caprylyl Alcohol
- Caprylic Acid
- Glyceryl Caprylate
Other fragrance components have some preservative boosting activity
There are also some enzymatic systems that have been successfully employed in natural cosmetic formulations.
- Glucose Oxidase
Finally, there are some natural ingredients that have some antimicrobial functionality. They are not broad spectrum effective so should not be used as the sole preservative system.
- Tea tree oil
- Aspen bark extract
- Grapefruit seed extract
- Honeysuckle extract
If you are formulating natural cosmetics and need a preservative system, your best strategy would be to use some of the suggestions above. Admittedly, preserving products using only natural ingredients is difficult. Be sure to test everything you make multiple times until you are certain your preservative system will be adequate. And as always, make the products in as clean an environment as possible.