Your guide to preservatives in cosmetics.

What Are Preservatives and Why Are They Important?

Preservatives protect cosmetic formulations from microbial contamination and spoilage. They ensure product safety by preventing bacterial and mold growth. Preservation is crucial in both production and consumer use, especially when products are exposed to non-sterile environments. The biggest public health risk when it comes to cosmetics is microbial contamination. You can go e.g. blind from contaminated products. An under-preserved product is an unsafe product.

Common Types of Preservatives

The Classics (e.g. Parabens & Formaldehyde Donors): Once widely used due to their broad-spectrum efficacy but are now controversial due to consumer misinformation. Cheap and easy to use. Despite the fear mongering, these ingredients are well supported to be safe *as used in cosmetics*

Aromatic Alcohols (e.g. Phenoxyethanol & Benzyl Alcohol): Effective against bacteria but weaker against yeast and mold. Should be coupled with other preservatives/boosters to achieve broad spectrumness. Compared to Parabens & Formaldehyde Donors, these preservatives are needed at higher input levels, which translates to higher costs to consumers.

Organic Acids & Their Salts (e.g. Sodium Benzoate): Good against yeast and mold but limited by low pHs (~below 4.5). Should be coupled with other preservatives/boosters to achieve broad spectrumness. Like the aromatic alcohols, these preservatives are needed at higher input levels, which translates to higher costs to consumers.

Multifunctional Ingredients: Offer some antimicrobial benefits while serving additional roles (e.g., moisturizing), though they generally require combination with other preservatives. Like the aromatic alcohols and organic acids, these preservatives are needed at higher input levels, which translates to higher costs to consumers.

Did you know parabens are some of the most well studied ingredients used in cosmetics? They are overwhelmingly supported to be safe. They also seem to be some of the most skin friendly, especially considering the total formulation context. E.g. they frequently win the non-allergen award of the year by the American Contact Dermatitis Society. No, paraben-free is not the “cautious option.”

Misconceptions About Preservatives

Natural options are safer! A challenge with natural ingredients is their consistency in terms of raw material composition - due to their variability, they can be inconsistent in efficacy. This leads to a significant safety risk for finished products. As a consequence, most of the preservative options out there are synthetically produced (even if they can be found in nature). This is to ensure that they are safe in the context of finished products.

Paraben-free is the “cautious option”! Parabens have significantly more safety data compared to other preservative options. The body of evidence, and not just a few single outlier studies, overwhelmingly supports safety. Their ease of use also represents a safety benefit - the move away from these preservatives is not without risk. In what world is something that has less data a “cautious option”? Reality, paraben free is the ignorant choice. It’s the one that panders to misinformation - which is fine, businesses have to be able to sell products to stay in business. But let’s call a spade a spade.

Formaldehyde-donor preservatives are toxic! Red-flag, anyone who calls something “toxic” without talking about the dose nessassary for the ingredient to cause harm. Virtually anything can be toxic, even oxygen. It’s the dose that makes the poison. Formaldehyde donor preservatives ARE NOT THE SAME THING as adding straight up formaldehyde. The amount of formaldehyde these preservatives release is equivallent, for a full finished product, to about the amount present in a pear. Or maybe a breath we exhale. Reality, these preservative types have good safety data, and are particularly useful in certain product categories due to their chemistry.

Waterless formulas don’t need preservatives. There is still moisture in the environment that can cause products to go moldy. E.g. lipsticks - it is not uncommon for microbial blooms to happen on the lipsticks during development if there’s no preservatives. Or eyeshadow pallets. Those don’t contain water, however there are many case examples of mold growing on eyeshadow. Preservation is still important in anhydrous formulas!

It’s easy to sub out one preservative for another. Absolutely not, especially when we’re talking about the newer preservative options. Preservative systems will have different use levels (e.g. classic preservatives may be used at ~0.1% while newer preservatives, closer to 1%), different pH ranges (e.g. the organic acid preservatives generally have to be in formulas below pH of 4.5... other ingredients in the formula also have specific pH tolerances which may or may not be compatible), different water solubility (for them to be effective, they have to stay in the water-phase of the formula where microbes grow), etc. This changes the whole formula. In terms of e.g. esthetics, viscocity, appearance, performance, skin safety, etc.

The constant ingredient bans from different retailers, also certain states (e.g. New York state is currently considering banning all parabens and formaldehyde donor preservatives... this consideration is based on misinformation. Misinformation also impacts the legislative level) creates a significant burden for brands to constantly have to reformulate - the reformulations, based on the evidence, aren’t going to make products safer... they may actually make them less safe in terms of potential for microbial contamination and skin safety. It certainly is going to make the products more expensive to produce... this cost will be passed down to the consumer.

Why are paraben-free products so much more expensive?

Because the newer preservative options are both more expensive (price doesn’t = better, economies of scale has a lot to do with this) and have to be used at higher input levels to have comparable efficacy. Development costs may also be higher due to the fact they are harder to work with. Reality, the benefit to consumers is very unclear... and there are definitely very clear downsides.

Other notes

Production Risks: Manufacturing environments can harbor persistent microbial contamination (e.g., biofilms in water systems). Continuous microbial monitoring and challenge testing are essential. Even if a product initially passed a preservative efficacy test (PET), they can still be at risk of being contaminated during production, particuarly if the manufacturing microbes are different than the microbes a product is challenged with in PET testing during product development. This also highlights the importance of Good Manufacturing Practices/clean production facilities.

The Waste Factor: Poor preservation leads to recalls and waste, because consumers may not use the product in time if the product has a short shelf life, which is a major sustainability issue. Longer shelf life = less waste = (often) better sustainability.

Future Innovations: Some ingredient companies are exploring biotechnology and fermentation for greener preservatives. The "holy grail", in terms of what the cosmetics industry wants, would be a low-cost, naturally derived, broad-spectrum preservative with no formulation issues, but this doesn’t yet exist.

Based on my podcast episode, A deep dive into cosmetics preservatives. All you ever wanted to know about preservatives... and more! In conversation with microbiologist and preservative expert, Sabrina Behnke PhD. Find the podcast here!