How to formulate without preservatives

Preservative free tip #1: It’s not really preservative free if the material is acting as a preservative

There are several ‘preservatives’ out there that say you can claim ‘preservative free’ if you use their material. This is not what this report is about. This is about truly preservative free formulations – formulations that are created to be self-preserving, and not using these so called ‘preservative-free preservatives’. If you require a so called ‘preservative-free preservative’ to protect your product from microbial contamination, then the material, no matter what class or function you say that material is performing in the product, is acting as the preservative.

Preservative free tip #2: Where A_w<0.6, no preservative is necessary

Where a formula contains less than a measured 0.6 ‘available water’ then it will not need a preservative. Be careful though, an available water result of 0.6 actually correlates to around 5% or less water in the formula, but should still be checked, to ensure it won’t need a preservative. Good examples of this are powdered products, oil based products and w/o emulsions with less than 5% water content. Be careful though, if significant water is introduced to a product over its shelf life (through consumer misuse or very humid environments) your product may exceed this available water input at some point, and then need preservation.

Preservative free tip #3: High alcohol or humectant content can make a product self-preserving

Generally, you are going to need >20% alcohol or >40% humectants to make a product ‘self-preserving’; while using small contents of humectants, can actually ‘feed’ micro-organisms. Use a lot of these materials to self-preserve or use a preservative – don’t risk it! Some examples of where this works well: aerosol products or sanitising hand gels typically contain over 20% ethanol; while you may find humectant-based scrubs or masks with a high content of humectant.

Preservative free tip #4: Products with extreme pH are self-preserving

If your formula has a pH < 3 or > 10, it will be self-preserving. Obviously, there are not many products that meet or suit this criteria, but you may be creating a very acid skin peel, or naturally saponified product or depilatory agent, in which case this environment is often unavoidable to achieve product efficacy. Be careful of other skin irritations when using extreme pH; this should only be done where the products/raw materials performance requires these sorts of extremes, otherwise they should not be used.

Preservative free tip #5: Pasteurise and use airless packaging

If you pasteurise your product during manufacture (and of course ensure pasteurisation occurs properly, not just heating but rapid cooling as well, even to the core of the batch) AND then pack it off into airless packaging, you may effectively remove any micro-organisms from the product and prevent any air or consumer introductions. You also need to avoid any potential condensation during the filling step. All things considered, if your product can achieve this, then you don’t need a preservative – however, if you are using this approach, every batch needs to be carefully tested for any viable micro-organisms, including the presence of spores. This approach does run risk of contamination during production and requires totally tamper-proof packaging to prevent consumer or air contamination at a later stage – make sure to check your batch carefully before releasing for sale if using this approach!

Now, let’s talk about some well-meaning tips that are on the internet that you need to be aware of:

• Certain herbal extracts and/or essential oils will reduce your need for preservatives: MOSTLY FALSE. The truth is, while some essential oils or herbal extracts have selective anti-microbial effects, to provide these effects they generally need to be used in quantities that far exceed the amounts that should be used in cosmetic products and/or they are not broad spectrum enough to be sufficient coverage of a cosmetic product over a 2–3-year shelf life.
• Antioxidants will reduce your need for preservative: TOTALLY FALSE. In fact, antioxidants are generally used in sufficient amounts to act as a food source for micro-organisms, further emphasising the need for good preservation! Antioxidants act to extend a products shelf life by protecting against oxidation, but do not protect against microbial contamination.
• Quaternary agents in cosmetics will enhance preservation: MOSTLY FALSE. While quaternary agents are used in many household products to enhance or preserve the product, they need to be in a highly alkaline environment to perform this activity. Quaternary agents in personal care, by comparison, are generally used in acidic conditions for their skin or hair conditioning benefits at lower pH, making any potential anti-microbial activity void due to the pH of the finished product.

Ultimately, not using a preservative is a far greater risk to a consumers’ health and wellbeing, not to mention your brand, than formulating preservative free formulations carefully or selecting a preservative to suit the end consumer use of a product. Make your selections well or formulate carefully to prevent microbial contamination throughout the product’s shelf life.