Written By Mira Aguirre
Article Summary
- What are preservatives?
- How preservatives work and why we need them in our products
- Broad spectrum preservatives, helper ingredients, and other formulation considerations
- The great safety debate
Preservatives. A word that doesn’t exactly evoke the same excitement as sexy ingredients like peptides or Vitamin C. But while they don’t bring to mind the image of glowing, hydrated skin, they are no less important - without them, your products wouldn’t be safe to use.
Cosmetic Ingredients
In skincare, there’s a lot of discussion on “actives.” This is a tricky topic as while there may be evidence behind ingredients like ascorbic acid and peptides, we cannot make drug claims about cosmetic ingredients. This means that unless it’s an Over the Counter (OTC) drug, we cannot claim that any ingredient will influence the structure or function of the skin - and calling cosmetic ingredients “actives” can imply that. A better term used in the industry by chemists is functional ingredients, cosmetic ingredients that offer a benefit to the consumer.
In addition to functional cosmetic ingredients like retinoids, exfoliants, and antioxidants, we have other categories of ingredients that make up the rest of the formula. They are equally important as without them, we wouldn’t have a product that is stable or enjoyable to use. While chocolate is the best part of a chocolate cake, you still need eggs and flour.
Before we delve into preservatives, let’s briefly go over some of these categories.
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Stabilizers. Ingredients like preservatives, chelators, and even emulsifiers that keep a product from separating, spoiling, or changing color/texture/efficacy.. They keep the product stable and safe to use.
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Sensorial and Aesthetic Ingredients are added to influence the texture, feel, application, and overall experience of using a product. This can include thickeners, emollients, colorants, and even fragrance.
Diluents and Solvents. There is no such thing as “fillers” in cosmetics as even water fulfills a key function. Ingredients need to be dissolved and diluted down to their recommended usage rate otherwise they can be irritating (and no one wants to rub a powder or other raw ingredient on their face.)
How Preservatives Work
In simple terms, preservatives keep icky things from growing in your cosmetics. No one wants to reach for their favorite moisturizer only to realize that a product they’ve purchased has spoiled. That’s not only a waste of your money but a serious safety concern.
We’re surrounded by microorganisms. Our own skin has its own diverse community of tiny bacteria, viruses, and yeast too small for the naked eye to see, called the skin microbiota. This is nothing to be afraid of as many of these microorganisms are crucial to our skin’s health.
A cosmetic product that has spoiled could be teaming with infectious microorganisms, which may overwhelm our immune defenses, throw off the balance of our skin microbiota, and get into our body. In addition to the risk of infection from microbial contamination, products that aren’t stable won’t be as effective. Preservatives are added to prevent the growth of any microorganisms that a product comes in contact with. But it’s not as simple as tossing in a preservative and being done.
There’s a lot that goes into selecting the appropriate preservative for each individual formulation. Depending on the formulation, “helper” ingredients may also be required to boost the efficacy of the preservative system used as well as other preservation methods like hurdle technology (combining different preservation methods) and sterilization (destroying all microorganisms). And it doesn’t end there - when a product undergoes testing before hitting shelves, it’s not just tested to make sure it doesn’t spoil. We actually do preservative challenge tests, where we add a few of the most common bacteria and molds to the formula; in order to pass the challenge test, those microorganisms have to dwindle down to zero over a few days. In other words, the preservative system needs to be strong enough that it doesn’t just protect from bugs, it can keep a formula safe even after contamination.
Preservative Types and Formulation
In cosmetics, the presence of water means there’s potential for microbial growth. This includes aqueous (water based) products like toners and serums, emulsions like moisturizers and cleansers, and even products like oils if they’re designed to be used in the shower. This also includes “waterless” skincare that uses aloe vera, hydrosols, or other water-containing ingredients.
In addition to water, there’s a few other things that can make a product more favorable for microbial growth. Nutrients, temperature, pH level, and oxygen are some of the main ones though it can depend on the type of bacteria or microorganism in question. We consider all of these factors when formulating our products as that will directly impact which preservatives will work best.
Preservatives should be “broad spectrum,” meaning they protect against all the microorganisms that can be found in cosmetics. You wouldn’t want to add a preservative that only protects against certain strains of bacteria or doesn’t protect against fungi. Luckily, there are many available options from manufacturers now with a lot of information available on what formulations they work best for. And testing of the final product should always be conducted.
We won’t bore you with an exhaustive list but here’s a few that you’ll see popping up in your skincare!
Germall Plus
INCI: Propylene Glycol (and) Diazolidinyl Urea (and) Iodopropynyl Butylcarbamate
Excellent broad spectrum preservative great for water based products and moisturizers as well as wash off products like cleansers.
Germaben II
INCI: Propylene Glycol (and) Diazolidinyl Urea (and) Methylparaben (and) Propylparaben
Broad spectrum and parabens are most of the most well studied, well tolerated preservatives on the market. Requires a pH range of 3-7.5 and doesn’t work well if there’s too many oil soluble ingredients.
Optiphen
INCI: Phenoxyethanol (and) Caprylyl Glycol
A popular option for brands marketing to consumers who want to avoid other preservatives like parabens. Works well and can be used to preserve products containing mostly oils but may not be active enough against yeasts and molds for all formulations.
In addition to preservative systems, formulators will also add various “helper” ingredients that boost preservative efficacy. Ethoxydiglycol, a solvent and penetration enhancer, is one such example. Chelating agents like disodium EDTA help metal impurities from discoloring the formula and aid stability. While chelating agents, antioxidants, and other helper ingredients aren’t substitutes for preservatives, they boost their efficacy - and are important for tricky to preserve products.
The Debate on Safety
It’s impossible to be on social media and not notice the many posts raising concerns over the safety of cosmetics. Preservatives in particular are often maligned and content that plays off our fears is more likely to get views and clicks, making it feel like we’re constantly hearing about the dangers lurking in our skincare products.
Ultimately though, it comes down to science. And lucky for us, there’s a huge amount of data looking at the safety of cosmetics. In addition to this evidence and the Food and Drug Administration (FDA), we also have the Cosmetic Ingredient Review. This independent panel has been performing safety assessments for over 40 years, like this one on parabens, and helps develop safe usage rates. And of course we have an entire field dedicated to determining the safety of medications and other substances we come into contact with - toxicology.
Toxicology Principles
Mohammed Kanadil (@moskinlab) is a toxicologist and pharmacist who works as a safety assessor of cosmetics. According to Kanadil, even harmful substances have a hard time getting into our body as it’s been specifically designed to keep out anything harmful - with multiple organs that can assist in removing toxins from our body. As a result, we really don’t need to be too worried that everyday substances we come into contact with are harming us.
There are some basic principles behind toxicology that we can apply to cosmetic safety: the dose of the ingredient and the route of administration as well as duration, frequency, and bioaccumulation. When it comes to dose, Kanadil says “everything can be toxic with the right dose and the question is always when a chemical is going to be toxic, not whether a chemical is toxic or not.” For example, he stresses even water can be toxic if you drink too much.
In addition to the dose, the route that a cosmetic ingredient or drug is being applied is also considered in regards to establishing safety. Kanadil says that when it comes to the route of exposure, “generally we are looking at how much of a chemical is getting into the bloodstream. Because of this, the most serious route will be intravenous medications while topical administration is last because the skin is an amazing barrier.”
Some other important considerations are the duration and frequency that an ingredient is being applied as well as bioaccumulation (how much of an ingredient is accumulating in the body). Kanadil stresses that duration is important because “the amount of time an ingredient stays on your skin will affect how much your skin absorbs.” And that’s not all, aggregate exposure (exposure from all sources and routes) and cumulative exposure (total exposure) are one of many other considerations when assessing ingredient safety.
You can learn more about toxicology by following Mohammed Kanadil on Instagram and YouTube.
Preservative Safety
Parabens and formaldehyde-releasing preservatives are subject to the most scrutiny. Despite being some of the best tolerated and safest preservatives, parabens have been unfairly demonized ever since a 2004 study on breast cancer was misinterpreted. (Our founder, Alli, walked through the issues with that study in this TikTok video.) Concerns over endocrine disrupting ability are similarly overblown as the studies show they are thousands of times weaker than our own hormones and therefore unlikely to disrupt them. The reality is that many alternatives to parabens don’t have the same level of safety data behind them.
Okay, what about formaldehyde releasing preservatives then? Formaldehyde sounds scary. After all, it’s used in embalming fluid and there’s some concern over it causing cancer. But like any toxicologist will tell you, “the dose makes the poison.” Formaldehyde is naturally occurring - our bodies produce it daily as part of our normal metabolism and we consume trace amounts daily in fruit, veggies, and some meats. Formaldehyde releasing preservatives release less than the amount found in a medium pear and like parabens, there’s lots of quality research on their safety.
At the end of the day, preservatives are an essential component of any cosmetic product. They ensure that the skincare we were using remains effective and is safe to use. Contaminated products have an established risk to our health while preservatives have a long track record of safety. Stratia selects ones that are highly effective for each specific formulation and backed by robust safety data. So when you see preservatives in the ingredient deck, remember this post and everything these ingredients are doing for that product!
References
https://chemistscorner.com/8-types-of-cosmetic-ingredients-in-formulas/
https://openstax.org/books/microbiology/pages/13-1-controlling-microbial-growth
https://www.fiosgenomics.com/microbiome-vs-microbiota/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9436228/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6099538/
https://cdn.shopify.com/s/files/1/0026/8317/5001/files/TIB_VC-850_Optiphen.pdf?v=1686081230
Mira is a skincare educator, blogger, and the content creator behind Skin Science by Mira and The Skincare Forum on Facebook. While skincare keeps her busy, she’s also pursuing her degree in Nursing and loves to spend her free time hiking. As a content writer for Stratia Skin, Mira shares her evidence-based approach to skincare topics and a passion for making science accessible.
