Does “Clean” Beauty Have A Mould Problem?

Growing beauty communities on social media platforms like TikTok and Reddit have effectively democratised the industry by giving beauty fans the power to amplify their praise and concerns around products and brands. While that feedback can be indispensable to other shoppers making their own purchasing decisions, it’s not always good news for brands — like Kosas, the “clean” beauty brand whose beloved Revealer Concealer recently entered the conversation for all the wrong reasons.

In January, a Reddit thread from last June, in which a user claimed to have found mould in their 13-month-old tube of Revealer Concealer, was discovered and recirculated on TikTok. The accusation quickly went viral, with other TikTokers coming forward to say that they also believed their concealer had turned, citing inconsistencies in smell and appearance.

The resulting conversation didn’t stop at Kosas. The TikTok community was quick to cast aspersions at not only the brand, but the “clean” beauty category as a whole, newly wary of whether the preservatives used in those products are adequate to keep them safe.

Clean, or non-toxic, beauty is a broad, non-scientific and non-regulated term generally used by brands that avoid synthetic compounds — including preservatives like parabens, widely used throughout cosmetics for decades. Dubious claims have been driving the notion that clean beauty is inherently better for a user’s health for years. Parabens in particular have long been a hot topic, with detractors claiming that their presence in cosmetics can cause breast cancer through hormone disruption, though that has been debunked by both the U.S. Food and Drug Administration and the European Union’s Scientific Committee on Consumer Safety.

Despite the evidence to the contrary, some people remain leery about synthetic preservatives, which is why “clean” beauty brands tend to eschew them. But does that mean you have to choose between using “chemicals” that the “non-toxic” beauty community has been vilifying for years or concealer that develops a “blue cheese smell”? We asked cosmetic experts and “clean” brands to break down what’s going on — and why you can, and should, remain calm.

On the whole, nearly all cosmetics companies are using some form of preservatives as they work to combat the slipperiest of culprits: water. “Looking at cosmetic products, 99% of cosmetics in the market are water-based,” says Krupa Koestline, founder of KKT Consultants and a cosmetic chemist specialising in “clean” beauty product development.

Given water’s ubiquity in and around cosmetic products, Koestline explains that, “in order to avoid the growth of any microbes, and therefore an infection risk, cosmetic chemists always use preservatives.” Products that claim to be formulated without preservatives as part of perceived “clean beauty” standards actually pose a serious health risk. “Microbes, particularly bacteria and fungi, readily grow anywhere that is humid and has available nutrients,” says Koestline. “Products are also used in non-sterile environments, like your bathroom, and come in contact with millions of microbes any time they’re opened or come in contact with your skin.”

As for “natural” preservatives (like sodium benzoate and phenoxyethanol) vs. “chemical” preservatives (like parabens), Koestline says that there really needn’t be a distinction. “All preservatives, even the ‘natural’ ones, are lab-derived,” she says. “The big question is whether the preservative of choice works in the formula as a whole.” The Journal of Cosmetic Dermatology published a study in 2021 indicating that some preservatives in cosmetics do have the potential for skin irritation, and Koestline notes that preservatives that have been linked to this or adverse health effects, including methylisothiazolinone, BHT, and diazolidinyl urea (among others), should naturally be avoided if you have a sensitivity.

With that said, Esther Olu, cosmetic chemist and licensed aesthetician, advises that “science is a lot more complex than brands, marketing, and sensationalism make it to be,” noting that there isn’t substantial evidence indicating that preservatives in cosmetics cause harm to humans. Olu does mention that everyone’s skin is different. If you find yourself sensitive to one preservative or category of preservatives, then you should avoid it.

If a product contains water, preservatives are more of a “need to have” than a “nice to have,” says Olu. “Preservatives are necessary to keep our cosmetics safe, especially during their intended use and overall shelf life,” she explains. There are some instances in which preservatives might not be technically necessary, like if a product is entirely water-free (as in the case of an oil or balm) or has a very low or very high pH level.

Speaking to beauty and personal-care brands across the industry, the embracing consensus is that user safety and shelf stability are paramount. The “clean” beauty companies we spoke to reinforced their commitment to testing and ensuring efficacy. 

“It is of the utmost importance to us to develop clean and safe products, which means having formulas that pass full micro testing. This ensures the preservative system is strong enough to ward off mildew [a type of fungus], mould, and bacteria,” says Emily H. Rudman, founder of clean beauty brand Emilie Heathe. “In some formulas this can mean relying solely on one preservative, like phenoxyethanol, or utilising multiple systems. The type of formula and the amount of water contained in that formula often determines how we proceed.”

Alyson Wilson, VP of Brand Innovation at Alo Beauty & Wellness (a division of the enormously popular activewear brand), says that Alo’s products similarly undergo extensive testing for both preservative efficacy and product stability. “Together, both tests can assess the quality of the products’ preservation system, evaluate their physical, chemical, and microbiological integrity, and their ability to resist common stressors, such as extreme temperatures,” says Wilson.

On Kosas’ end, the brand has been responsive to consumer concerns. In a reply to a TikTok video, Kosas assured its extensive fanbase that it uses “safe, broad-spectrum preservatives that are effective against mould.” (Kosas declined Refinery29’s request for comment.) The updated FAQ page on the brand’s website states that Kosas uses “safe, effective preservatives and antimicrobial stabilisers which prevent mould, yeast, and pathogens. All products must pass rigorous preservative efficacy testing in accordance with the USP 51 protocol by an independent analytical lab for us to bring a product to market.” The USP 51 test method, which is used to determine the effectiveness of a material's antimicrobial preservatives, involves incubating test samples and determining the number of living microorganisms at various intervals over the course of 28 days.

Other brands we spoke with are approaching preservation from a different angle — with the understanding that water is causing moulding, they are choosing to work with a lot less H2O, and therefore cut back on the need for preservatives. 

Cosmetics brand Lush says that minimising water content in its line of "self-preserving" products eliminates the need for a high level of synthetic preservatives, which the brand claims can "deplete the natural diversity of your microbiome" (the community of microorganisms that form part of your skin barrier and have an important role in protecting from infection). The formulations, including the new Peace Self-Preserving Moisturizer, employ naturally antimicrobial ingredients like salt, honey, and cocoa butter in lieu of added preservatives.

“Water is an essential skin-care ingredient and important to formulate with, but it's also an ideal medium for microbial growth, which has to be considered when making a product,” wrote Helen Ambrosen, Lush co-founder, and Milly Alqhuist, Lush skin-care category lead and researcher, in an email to Refinery29. The easiest and cheapest way to deal with this is to use a preservative. “At Lush we have pioneered ways to reduce our use of preservatives and create entirely self-preserving formulas, as defined under Annex 5 of the E.U. Cosmetic Regulations [the list of preservatives allowed in cosmetics in the E.U.] because we recognise their potential for irritation and don't think they are beneficial for your microbiome.”

Lush reports that around 90% of its core range in 2022 was self-preserving, and 86.9% of global Lush product sales between 2021 and 2022 were from customers purchasing self-preserving products. The company conducted microbiological testing by comparing the stability of the preserved products to the self-preserving. For self-preserving products, Lush looked at the microbiology levels of testers' samples when first made and then after use at around the three-month mark and again at six months to ensure that the product is stable to the very end of its shelf life. 

Speaking of shelf life, it is crucial that the self-preserving products be used strictly by their expiration dates (as should all cosmetic products, generally), as they are not intended to have extended shelf lives. Many clean beauty products, including Kosas’ concealer, list expiration dates as soon as six months after their on-sale date. The fewer preservatives there are in water-rich formulas, the faster they will expire.

Cosmetic and skin-care brand NUDESTIX is also conscious of water content, says president and founder Jenny Frankel. “Many of NUDESTIX formulations are cream anhydrous-based [no water present] and therefore can have preservative-free formulations,” she explains. “However, to provide extra microbial protection from potential cross contamination by consumers, we choose to use low levels of phenoxyethanol.” Phenoxyethanol is a popular preservative in “clean” beauty as it can be found naturally in green tea and chicory; it is developed in a lab for cosmetic use.

Despite every brand’s best efforts, you should still always trust your sense. “Just like you examine food for smell, colour, and consistency before consuming, so should we be examining the products applied to our skin, as this gets absorbed by the body, too,” says Kseniya Kobets, MD, Director of Cosmetic Dermatology at Montefiore Advanced Care. “If you see any mould inside any product, you should not use it. Bacteria- or mould-ridden products applied to skin can cause irritation, or worse, an infection, especially if your skin is sensitive or eczema-prone.”

So, while it’s still important to remain vigilant, make sure your products pass the sniff and sight test. There’s no real need for panic. Preservatives in cosmetics are doing their job efficiently and keeping your products safe — and, most importantly, the vast majority of brands are approaching product preservation thoughtfully and directionally. Just pay attention to those expiration dates.