Preservatives Part Two: Effective Usage
As you may remember from our last post about preservatives, any time water is incorporated into your cosmetic products, with a few exceptions, looking to a preservative or preservation system is key to ensure you’ve got a safe end product. Not preserving it - you’re opening your formulations up to be a breeding ground for potentially very pathogenic bacteria. No matter how sterile the manufacturing space and packaging are and how careful we are making the products, as soon as water is introduced into a formulation, microbial growth is inevitable, especially considering how consumers usually treat their products (open jars in a steaming bathroom? Not the best habit for your beauty products). For more on this, read our guide to cosmetic preservatives - highly recommended before you dive into this article :). In this post, we’ll explore the details on how to actually choose and use preservatives effectively in your product formulations. This isn’t going to be an exhaustive review by any means, but hopefully, a good place to start to understand this important topic!
What do preservatives do?
Definition of preservative from the Merriam-Webster Dictionary: something that preserves or has the power of preserving; specifically: an additive used to protect against decay, discoloration, or spoilage
Preservatives have two main functions, kill microorganisms (microbicidal) and prevent their growth (microbistatic). Typically the microbicidal preservatives are the go to’s for cosmetic products, but with the push to natural in the personal care space, microbistatic agents are becoming more popular. While there’s lots of variation of effects based on which preservatives you choose, preservatives are all potential irritants. As a result, they should always be used at a minimum concentration necessary to effectively preserve the product, and always within their regulatory limits (sometimes different in different countries - look to yours for the best information on this. E.g., in Canada, look to Health Canada, the USA, the FDA, in Europe, the EU and COSing).
A few examples of things that may affect preservation
Ingredients: Some ingredients are more prone to contamination and should be routinely checked for this, for example, many colors, gums, clays, proteins, and ingredients with high water content. Making sure you have a good supplier and, again, testing your ingredients out, is a pretty key step for manufacturing products. Other things to be aware of include how you handle them, store them (e.g. does the ingredient need refrigeration?), expiry dates, etc.
Packaging: The packaging you use has a big impact on how you’ll have to preserve your product. For example, airless packaging with a product that never comes into contact with you or the environment will likely need less preservatives than a cream in a jar that you stick your fingers in to use.
Formulations: If you don’t have a stable product, that’s going to have a serious impact on how your preservatives are able to actually function. Different formulating decisions can also lower microbial contamination risks. For example, using low amounts of water, using humectants (e.g. glycerin) which are antimicrobial themselves, formulating at a high or low pH (bacteria and yeasts prefer pHs of roughly 5-8 -pHs of higher than 9 or less than 4 will prevent a lot of microbes from growing), high amounts salt or sugar (note, low amounts may have the opposite effect), essential oils, alcohol, etc. I’m not recommending relying on any of these methods to not use preservatives, but they do make your formulations a lot less prone to contamination... This thought process is at the stem of the whole ‘natural hurdle’ way of preserving products, but this topic is beyond the scope of this blog post.
Good Manufacturing Processes: Poor sanitation can open your products up to contamination. How you make your products also has a big impact - e.g. pasteurization (heating your hot phase ingredients over 71.6C followed by rapid cooling) is a good tool to use for products that need heating, batch size changes can impact how you need to preserve your products, the water you use (e.g. you should always be using purified water rather than tap water), etc.
Challenge Testing: Any time you formulate, especially if you’re planning to sell your products, you should probably be challenge testing to get a gauge of whether they’re safe and your preservative system is effective. This also helps to figure out the minimum amounts of preservatives that are needed to effectively preserve your products. I’m not going to go into any detail about this, as this topic would easily take up a full blog post. If you’re a new beauty manufacturer, I would highly recommend working with a lab to test your products.
Selecting your preservatives
Consideration 1, Broad Spectrum Activity
This is key to making a safe product. When you choose your preservatives, you want to make sure the preservative blend (note, you can buy pre-blended systems, which are WAY easier to use as a new formulator) should have bactericidal as well as fungicidal activity, covering the whole gamut, from gram-negative to positive.
Consideration 2, Compatibility with your Formulation
Preservatives, just like many other raw materials, are often stable in set ranges. For example, some may be stable at a pH of 4-6, some pH 3-12, some only under 30 degrees Celsius, some may not be compatible with different ingredient types (e.g. ionic vs cationically charged), and so on and so forth. Is it water or oil soluble? If you're making a product with mostly water, e.g. o/w emulsion with water as the continuous phase, you'll want to opt for water-soluble. When you're choosing your preservative, this is key! Not considering this for your product - you may end up with a pretty well unpreserved product...
Consideration 3, Does it fit into your ethos?
For example, are you keen to use only ‘natural’ (or nature identically more likely) or EcoCert options? If this is something you’re looking for in a preservative, you’ll want to look into this when choosing them. When evaluating ingredients, always ask your supplier for challenge testing information, INCI name (perhaps also the CAS number), and maybe even details on their natural status (e.g. via product data sheets).
End product (e.g. water concentration, packaging, etc), where the product is going to be used (e.g. you probably don’t want to be using preservatives that are higher in the irritancy on sensitive skin types or even the face in general), regulations, and cost/availability.
There are many preservative options out there. To make things easier for you, I’ve compiled a list of easy to source preservatives available through Canadian suppliers with very low to no minimums. There are lots of other preservatives out there - to access some of the more innovative ones though, you may have to order directly through manufacturers (who have far higher minimums).
Liquid Germall Plus: Broad spectrum, synergistic preservative effect. INCI: Propylene Glycol, Diazolidinyl Urea, Iodopropynyl Butylcarbamate. Natural Status: synthetic. Recommended Usage: 0.1-0.5%. pH range: 3-8. Add at 50 degrees Celsius or below. Available through New Directions Aromatics, Voyageur Soap and Candle, Saffire Blue.
Geogard ECT: Broad Spectrum. INCI: Benzyl Alcohol, Salicylic Acid, Glycerine, Sorbic Acid. Natural Status: Nature Identical, EcoCert approved. Recommended Usage: 1%. pH range: 3-8. Add at 45 degrees Celsius or below. Available through Voyageur Soap and Candle, Saffire Blue.
Germaben II: Broad Spectrum. INCI: Propylene Glycol, Diazolidinyl Urea, Methylparaben, Propylparaben. Natural Status: Synthetic. Recommended Usage: 0.3-1%. pH range: 3-7.5. Add at 60 Degrees Celsius or below. Available through Voyageur Soap and Candle.
LiquaPar Optima: Broad Spectrum. INCI: Phenoxyethanol, Methylparaben, Isopropylparaben, Isobutylparaben, Butylparaben. Natural Status: Synthetic. Recommended Usage: 0.5-1%. pH range: up to 8. Add at 80 degrees Celcius or below. Available through Voyageur Soap and Candle.
Optiphen Plus: Broad Spectrum. INCI: Phenoxyethanol, Caprylyl Glycol, Sorbic Acid. Natural Status: Synthetic. Recommended Usage: 0.75-1.5%. pH range: up to 6. Add at 80 degrees Celcius or below. Available through Voyageur Soap and Candle, Saffire Blue.
Potassium Sorbate: Effective against yeasts, molds and select bacteria. Note, should be combined with another preservative for broad-spectrum effects. INCI: Potassium Sorbate. Natural Status: Nature Identical. Recommended Usage: 0.1-0.5%. pH: up to 6. Add at 60 degrees Celcius or below. Note, final products may be light sensitive - use a package that protects your product from light. Available through Voyageur Soap and Candle.
Sodium Benzoate: Bacteriostatic and fungistatic, should be combined with another preservative. INCI: Sodium Benzoate. Natural Status: Nature Identical. Recommended Usage: under 1%. pH range: up to 6. Add at 60 degrees Celcius or below. Good idea not to mix with vitamin C - some food studies indicate this preservative may react with vitamin c to form small levels of Benzene, a known carcinogen. Available through Voyageur Soap and Candle, Saffire Blue.
Suttocide A: Broad Spectrum. INCI: Sodium Hydroxymethylglycinate. Natural Status: Synthetic. Recommended Usage: .4-1%. pH range: 3.5-12. Add at 60 degrees Celcius or below. Available through Voyageur Soap and Candle.
Tinosan SDC: Broad Spectrum. INCI: Citric Acid, Silver Citrate. Natural Status: Synthetic. Recommended Usage: 0.1-0.3%. pH range: up to 7. Add at 50 degrees Celcius or below. Available through Voyageur Soap and Candle. Note, doesn’t play well with cationic ingredients. Note, final products may be light sensitive - use a package that protects your product from light. Available through Voyageur Soap and Candle.
Leucidal Liquid Complete: Antifungal and Antibacterial, should be combined with another preservative. INCI: Leuconostoc/Radish Root Ferment Filtrate & Lactobacillus & Cocos Nucifera (Coconut) Fruit Extract. Natural Status: ~Natural, EcoCert Approved. Suggested Usage: 2-5%. pH range: 5-9. Add at 60 degrees Celcius or below. Available through Saffire Blue.
Links for the listed distributors:
Alvarez-Rivera, G., et al. (2017). Preservatives in Cosmetics: Regulatory Aspects and Analytical Methods. Analysis of Cosmetic Products, 175.
Berthele, H., et al. (2014). Determination of the influence of factors (ethanol, pH and aw) on the preservation of cosmetics using experimental design. International journal of cosmetic science, 36(1), 54-61.
Carli, B (2017). Apply microbiology techniques for product safety. Diploma of Personal Care Formulation Text Book, Institute of Personal Care Science.
Halla, N., et al. (2018). Cosmetics Preservation: A Review on Present Strategies. Molecules (Basel, Switzerland), 23(7).