Introduction
In this blog post we are going to be discussing preservatives, what they are, how and when they get used, why it is important and also some examples of natural and synthetic preservatives you can use in your cosmetic formulations.
What is a preservative
A preservative is a substance that is used to inhibit the growth of microorganisms in cosmetic products. Preservatives protect your cosmetics from microbial contamination.
When do you need to use a preservative
If your cosmetic contains water or will be coming into contact with water such as a scrub it is IMPERATIVE for your and consumer safety a preservative is used. There are two types of micro-organisms we are concerned with in cosmetic formulation: fungi and bacteria.
Types of preservatives
When selecting appropriate preservatives there are three types you can choose from, fungicidal, bactericidal and lastly broad spectrum preservatives. Broad spectrum preservatives provide protection against both fungi and bacteria therefore this is normally the most appropriate choice.
To ensure your product has protection from both fungi and bacteria it is important to use a broad spectrum preservative.
On the issue of safety, there is a lot of misinformation regarding the safety of preservatives, I can assure you it is significantly more dangerous to not use a preservative where one is necessary.
Also it is important to note what a preservative is not, vitamin E oil (tocopherol) is NOT a preservative, it is an antioxidant. Antioxidants provide protection against premature oxidation which can result in the instability of your formula. This is only relevant when you are using plant oils.
Preservatives can come in different forms, liquid, and powder forms are the most common. Below I will give some examples of both synthetic and natural broad spectrum preservatives you can use.
Synthetic Broad Spectrum Preservatives:
Trade Name: Optiphen
INCI: phenoxyethanol, caprylyl glycol)
Usege: 0.75-1.5%
pH: 4 - 8
Heat tolerance: <80°C
Trade Name: Liquid Germall Plus
INCI: Diazolidinyl Urea, Iodopropynyl butylcarbamate
Usage: 0.1-0.5%
pH: 3-8
Heat tolerance: <50°C
Natural Broad Spectrum Preservatives:
Trade Name: Geogard Ultra
INCI: Gluconolactone, sodium benzoate
Usage: 0.75-2%
pH: 3-6
Heat tolerance: stable in heat
**this preservative can be naturally derived or nature identical so is not completely natural
Trade Name: Nipaguard SCA
INCI: Sorbitan caprylate, Benzyl Alcohol
Usage: 1-2.5%
pH - 4.5-8
Heat tolerance: <80°C
pH & pH drift considerations
Some other things to consider when selecting your preservative is pH, any product that contains water has a pH. Above in my examples of preservatives I gave a range of pH, this is the range that specific preservative is active in. If the pH of your product falls outside this pH range you risk deactivating your preservative, meaning there is no protection against microbial contamination and that you might as well of not added it.
Another thing to consider is what’s known as pH drift; the pH of your product will drift over its shelf live 10% either up or down, you need to account for this when selecting your preservative. For example if the pH of your product is 5.5 which is the most common pH for cosmetic products, the pH will drift 10% down or up. 0.55 is 10% of 5.5 so if you subtract (5.5-0.55) this will equal 4.95. If you add (5.5+0.55) this will equal 6.05. This mean the preservative you choose will need to be active at both 4.95 and at 6.05. There is no way to tell which way your product will drift either up or down, therefore is it imperative that your preservative accounts for this 10% drift.
Heat tolerance considerations
Another thing to consider when using preservatives is heat tolerance. If your preservative cannot handle high temperatures - and most preservatives can’t, you risk deactivating your preservative. Therefore it is important you know the heat tolerances of any preservative you use. A safe bet is to add your preservative in the cool down stage when your product reaches (below) <40°C.
Other considerations
If you are an at home formulator I recommend using the upper amount of preservative, this is because our homes are less sanitary and eaquipped than professional labs and therefore it is a good idea to use the upper limit to ensure you are getting the necessary protection against harmful micro-organisms. The trade off is firstly the more preservative you use the more the cost of your overall formula will be, secondly most preservatives are have high irritancy potential meaning the more preservative you use the higher the risk of irritation. You want to be able to use as little preservative as possible without compromising microbial contamination. You cannot know this unless you get PET (preservative efficacy testing) done on your formula to determine whether the preservative is effective in your formula and at what dosage. This is another reason to increase the dosage to the upper limit of what’s safe because the more preservative you have it stands to reason the more protection your formula has.
One thing I really want to stress, natural does not automatically mean better or safer, in fact many natural ingredients including essential oils contain allergens and irritancy potential.
Synthetic preservatives are not to be feared, when used according to their guidelines they are perfectly safe to use. Synthetic preservatives also tend to be cheaper, and needed in lesser amounts further making them more cost effective. Ultimately it is up to you what preservative you decide to use. Another thing to note about natural preservatives is many of them have a fragrance this may not be desirable if you want your product to smell a certain way, in this case synthetic preservatives can be a good choice and many of them are odourless.
Conclusion
In this blog post we have discussed what a preservative is, why we use them, as well as the different types of preservatives: fungicidal, bactericidal and broad spectrum. We have given some examples of natural and synthetic preservatives. We have also discussed important considerations when processing preservatives to ensure they are being used properly and effectively. I hope you have found this blog post helpful, and can refer back to it when needed.
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