Nowadays, preservatives are considered harmful and toxic substances present in cosmetics therefore, there is an emerging interest in “preservative-free” cosmetics. Are these products really preservative-free? Or even more importantly, is it safe to use preservative-free products? To better evaluate this let’s review some scientific evidence and basic concepts about preservatives.
Most cosmetic formulations have a high percentage of water or have active ingredients that can be easily degraded by microorganisms, and therefore are prone to deterioration. As the name suggests, preservatives are synthetic or naturally derived chemical ingredients that are incorporated in low concentrations to prevent or delay cosmetic products from degradation. Preservatives inhibit the growth of microorganisms by several mechanisms depending on their chemical structure and reactivity. These mechanisms include disruption of microorganism’s outer membrane, inhibition of protein synthesis, and acidification of the external environment making it unfavorable to microbial growth(1,2).
Why are they considered harmful?
Preservatives in cosmetics have gained a bad reputation since a study in 2004 showed that the oldest and most commonly used preservative was found in breast tumor tissue. And yes, I’m talking about parabens. Darbre et al.3 reported that parabens were detected in tissue samples from human breast tumors in 19 out of 20 patients studied, concluding that parabens and other chemicals in underarm cosmetics may contribute to the rising incidence of breast cancer. However, subsequent studies have discussed and raised some concerns about the study results and design. Harvey et al.4 stated that Darbre’s study cannot prove a causal relationship between parabens and breast cancer due to several limitations among which (1) the small sample size, (2) they did not identify the route of paraben assimilation, and (3) they did not analyze the parabens concentration in normal tissue samples. Therefore, the study did not have an appropriate control to compare the results with.
Moreover, at the time of writing, the Food and Drug Administration (FDA) states that there is not enough information to show/prove that parabens, as they are used in cosmetics, affect human health. Nevertheless, scientists must continue to evaluate new data in this area to review paraben safety 5.
Preservative-free products aren’t necessarily safe!
“Preservative-free” cosmetic products have been extensively promoted to the public even though they do have preservatives in their formulation. All cosmetics have to be preserved in a certain way to prevent the growth of bacteria, yeast, and mold above a certain concentration; for this, manufacturers use different strategies. One of these strategies is to use ingredients that are not commonly recognized as preservatives but are able to provide different levels of protection against microorganisms. These ingredients include antioxidants (butylated hydroxyanisole, tocopherol, urea, citric acid) and naturally occurring ingredients with antimicrobial activity that fall under another classification like emollients, humectants, etc6.
On the other hand, if you want to make your cosmetics at home completely preservative-free, keep in mind that their shelf life, even if they are refrigerated, will be limited to days. You should treat them like fresh fruits or vegetables and understand that since most of them will contain water and flower or fruit extracts, they are highly vulnerable to bacterial growth. Even if your cosmetic product does not include water in its formulation, the moment you use it with wet hands, the process of bacterial contamination begins2.
The preservative-free concept is just a marketing technique that can cause confusion and fear in consumers, but the bottom line is that preservatives are always a good option to protect your cosmetic from contamination and, if a product indeed has no preservatives listed on the label, be cautious.
Synthetic vs Naturally derived preservatives
So what are your options when choosing a preservative? Here are the benefits and drawbacks of natural and synthetic preservatives.
The commonly used synthetic preservatives are parabens (methylparaben, ethylparaben, propylparaben, butylparaben, isobutylparaben), aldehydes (formaldehyde, DMDM hydantoin, imadozolidinyl urea, diazolidinyl urea), glycol ethers (phenoxyethanol and caprylyl glycol), isothiazolinones and organic acids (benzoic acid, sorbic acid, levulinic acid, anisic acid). As advantages, synthetic preservatives have a broad-spectrum of activity against bacteria and fungi, their safety and toxicity profiles are well understood, they are required in low concentrations to work effectively, and generally, they do not interfere with fragrance, color, or other aspects of the formulation. However, as drawbacks, they are often based on petroleum and some consumers find them irritating on the skin 1,7.
Natural preservatives include alcohols (benzyl alcohol from burgundy rose and damask rose essential oil, farnesol, hinokitiol), phenols with antioxidant activity (ferulic acid, caffeic acid, p-coumaric acid, thymol), medium-chain fatty acids (glyceril caprylate from coconut or palm oil triglycerides), essential oils, and plant extracts. As advantages, they are generally preferred by consumers and some of them can provide a natural fragrance to cosmetics. As for drawbacks, they often do not inhibit microbial growth as well as their synthetic counterparts, often lack broad-spectrum activity, they may require relatively high concentrations in formulations to be effective and can cause skin sensitization and allergies1,7.
Taking everything into account, whether you prefer a synthetic or natural preservative, they have successfully preserved thousands of cosmetics and therefore are essential in cosmetics formulation to keep your products safe and fresh. I hope this article has increased your understanding of preservatives and helps you to make an informed decision the next time you buy a cosmetic product.
References
1. Id, Z. B., Boucherit, K., Rodrigues, E. & Ferreira, I. C. F. R. Cosmetics Preservation : A Review on Present Strategies. Int. J. Mol. Sci. 23, 1–41 (2018).
2. Anderson, E. Preservatives – Keeping our cosmetics safe & fresh. Michigan State University (2019). Available at: https://www.canr.msu.edu/news/preservatives-cosmetics-safe-fresh. (Accessed: 19th May 2020)
3. Darbre, P. D. et al. Concentrations of Parabens in Human Breast Tumours. J. Appl. Toxicol. 13, 5–13 (2004).
4. Harvey, P. W. & Everett, D. J. Significance of the Detection of Esters of p -Hydroxybenzoic Acid ( Parabens ) in Human Breast Tumours. J. Appl. Toxicol. 4, 1–4 (2004).
5. FDA. Parabens in Cosmetics. (2018). Available at: https://www.fda.gov/cosmetics/cosmetic-ingredients/parabens-cosmetics#are_parabens_safe. (Accessed: 19th May 2020)
6. Fraise, A. P., Lambert, P. A. & Maillard, J.-Y. Principles and Practice of Disinfection, Preservation and Sterilization. (2008).
7. Natural vs. Synthetic Preservatives. Microchem Laboratory Available at: https://microchemlab.com/information/natural-vs-synthetic-preservatives. (Accessed: 18th May 2020)