Introduction:
In this blog we will be discussing the use of preservatives in cosmetic formulation. We will be looking into what preservatives are, why and when we use them, the problems associated with preservatives as well as how they work. We will also be looking into why microbial contamination occurs and how to negate this.
What are preservatives?
Preservatives are substances that protect formulas against fungi and bacteria, they are vital components of cosmetics ensuring safe usage and necessary for an extended shelf life. There are different types of preservatives some that provide protection against fungi and some that provide protection against bacteria. In cosmetic formulas you need a preservative that provides protection against both fungi and bacteria, otherwise known as broad spectrum preservatives. In order to achieve broad spectrum preservation synergistic blends are used in cosmetic formulas.
Why are preservatives needed?
Preservatives are used to protect cosmetic products from microbial contamination. You only need to use a preservative if a formula contains water or will be becoming in contact with water such as a body scrub. This is because mould and bacteria need water in order reproduce, in addition to this they also require a food source and certain pH conditions. Because of this cosmetic formulas are a prime breeding ground for fungi and bacteria as most cosmetics contain water and various nutrients in the form of oils, actives and vitamins that are a food source, as well as falling into the pH range of 3-10 which both fungi and bacteria can survive in. Cosmetic formulas below a pH of 3 and above a pH of 10 do not require preservatives as fungi and bacteria are unable to survive in these conditions. Unfortunately very few cosmetic products come under these pH ranges meaning a large majority of cosmetic products require preservatives in order to achieve a suitable shelf life. Anhydrous products that do not contain water and will not be coming into contact water do no need preservatives. Therefore if you are a beginner I strongly recommend starting here before progressing to formulating products that require preservatives.
What are the problems with preservatives?
Preservatives have high risk irritation profiles and many are allergens, meaning when used in high quantities they can be irritating to the skin and cause allergic reactions. Many preservatives both synthetic and natural when used in large quantities can be very detrimental to human health for this reason there are regulatory limits on a majority of preservatives. It is extremely rare you will ever have more than 2% of a preservative in a cosmetic formulation, mostly they are used within the range of 0.5% - 1.5%.
The most effective preservatives are synthetic, many of us prefer to use natural or naturally derived ingredients therefore the synthetic nature of many of the highly effective preservatives may not suit brand ethos or our personal preferences. Broad spectrum natural preservatives are however available on the market. To be clear as long as preservatives are used within their regulatory limits they are safe for use on the skin. Be very dubious of sources that suggest otherwise many of the claims you see on the internet suggesting preservatives cause cancer, hormonal disruption are false and misleading. If anyone ever makes a claim like this ensure they have ratified scientific data to back up their claims. I have previously written another blog on reliable sources for cosmetic ingredient research where you can find the regulatory limits with detailed research conducted that lead to the determination of safe regulatory limits.
Another problem with the use of synthetic preservatives pertains to the non renewability of them and dangers they pose to terrestrial and aquatic life. On the safety data sheets of any material it will stipulate the biodegradability and the dangers it poses to both terrestrial and aquatic life. Take care to read these and determine what can be done to negate these issues.
How do you use preservatives?
Depending on the preservative you are using each material has a different set of conditions on how they can be used effectively. You can find this information on a safety data sheet and you can also contact your manufacturer for additional support. Please DO NOT use any material that does not have a safety data sheet accompanying it, because otherwise you literally have no idea what you are using, how it was manufactured and the purity and safety of the material.
Preservatives come in different forms, some come as liquid, some as fine powders, some as flakes or crystals. This is important because in order to effectively disperse your preservative throughout your formula you need to know how to use your preservative of choice. Otherwise you risk inadequately preserving your product and thereby risking microbial contamination. I prefer to use preservatives that come in liquid form as these tend to be easier to disperse into formulas, in any case always read the safety data sheet which will tell you how to use your preservative of choice. Depending on the preservative you use it will have stipulations regarding the pH it works within, the temperature you need to add it in, ingredients it is not compatible with and the percentage you need to use. Always adhere to these stipulations otherwise you risk deactivating your preservative and thereby reducing the efficacy of your product.
How do preservatives work?
Preservatives work in two main ways:
Microbicidal: Killing microorganisms resulting in the decrease of colony numbers. Bacterial spores may remain if the preservative is not strong enough to kill these too.
Microbistatic: Inhibiting growth and multiplication of colonies, but not killing the microorganisms currently present. Meaning the population will not grow any further. However further growth may occur if continued contamination is introduced into the product.
Microbididal preservatives tend to be the industry standard and are the more effective out of the two. Many natural preservatives tend to be microbistatic. It is very important to note natural does not mean better, in fact I as well as many other chemists would argue that when it comes to preservatives synthetic ones tend to be the better option.
How microbial contamination occurs
If you don’t use a preservative when necessary the risk of microbial contamination is exceptionally high. If you don’t follow the guidelines set by the manufacturer this can render the preservative in your formula redundant. However with that being said contamination can occur even if you use the right preservative following manufacturer guidelines this can happen for a number of reasons:
Raw materials: You need to regularly check your raw materials for contamination particularly water based materials. If these are contaminated you could be working your preservative so hard to the point it is not able to combat the contamination that is already there as well as any future contamination.
Equipment: Ensure that you are regularly sterilising and sanitising your equipment before and after use. If your equipment has been contaminated this can then pass into your formulas resulting in working your preservative too hard and reducing efficacy.
Poor air quality: Microorganisms can be present in the air, therefore it is important to operate in a well ventilated space that is regularly cleaned to ensure your products are not contaminated due to poor air quality.
Packaging: Ensure that your packaging is adequately sterilised and sanitised before you put product into it. If these are contaminated you could be working your preservative so hard to the point it is not able to combat the contamination that is already there as well as any future contamination. Also ensure your packaging is suitable for your intended formula, if you are unsure about this consult a chemist. As a rule of thumb wide neck jars are the highest risk packaging, airless bottles and sachets are considered low risk packaging, whilst disk tops bottles are considered medium risk. This risk is determined based on the ability for air to enter the product as well as contamination that can be introduced when the product is being used eg. Fingers in a wide neck jar.
A lot of this comes down to poor GMP (Good manufacturing process) you can learn more about this on the Cosing website. Although it sounds overwhelming a lot of it is common sense, I highly recommend becoming accustomed with the stipulations of GMP to ensure you do not fall victim to the above.
A note to home formulators
Many of you reading this will be home formulators and you may be thinking this is too overwhelming I can’t do this. I just want to impress on you that you can still formulate safe efficacious products from your home despite the potential risks, I and many others have been doing it for years without problems. It is important to be aware of the potential risks so you can put the necessary procedures in place to negate them. Ensure your formulating space is clean and sanitised, ensure you are storing your ingredients according to manufacturer guidelines - always keep ingredients in the packaging they came in. Ensure your packaging is sterile. When it comes to preserving your product I would use the maximum recommended amount of preservative to provide your products with that extra bit of protection. Whilst I appreciate the topic of preservatives can be daunting do not let it stop you from formulating, by reading this blog and following the guidance given you have done your due diligence. I hope you come away from this read feeling empowered and not put off.
Conclusion:
In this blog we have discussed what preservatives are, why and when we need to use them. We have also discussed how microbial contamination can occur, the problems associated with using preservatives and how preservatives work in cosmetic formulation. Please do adhere to the guidance given in this blog if you are formulating cosmetics that require preservatives and follow the guidance stipulated here for the best possible experience.