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The Current State of Preservatives
By: Ahmed Abdullah, MD
Posted: July 1, 2013, from the July 2013 issue of Skin Inc. magazine.
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New research by Darbre continues to raise more questions than answers about the effects of parabens. Her latest study demonstrates that parabens can induce the growth of breast cancer cells.9 Although any mention of cancer in relation to a skin care ingredient is alarming, the fact is that, yet again, this study fails to show that parabens cause cancer. In fact, certain herbs, such as dong quai and ginseng, have been shown to induce the growth of cancer cells.10 Thus, it is obvious that further research is needed.
Other popular preservatives have also been criticized, albeit to a lesser extent than parabens. Formaldehyde-releasers, such as quaternium-15, DMDM hydantoin, imidazolidinyl urea and diazolidinyl urea, are used in approximately 20% of cosmetics and personal care products.11 During a product’s shelf life, these preservatives release miniscule amounts of methylene glycol, the alcohol form of formaldehyde, which is a gas. Given that formaldehyde is considered carcinogenic by the World Health Organization’s International Agency for Research on Cancer (IARC)12, the relationship—albeit a very distant one—between formaldehyde-releasers and formaldehyde has made the public jumpy. But adding to their concern is the finding that when certain formaldehyde-releasers, such as bronopol (2–bromo–2-nitropropane–1,3–diol), are combined in a formulation with amines, such as Cocamide MEA or DEA, nitrosamines can be inadvertently created.13 Nitrosamines are carcinogenic substances with the ability to penetrate the skin.
The reality is that reputable skin care companies that choose to preserve their products with formaldehyde–releasers do so using the smallest necessary concentrations, the result of which is the release of minute levels of formaldehyde. What’s more, formaldehyde is carcinogenic when inhaled in large doses—a scenario that doesn’t apply to skin care products or cosmetics. Finally, cosmetic chemists understand the risk of combining formaldehyde-releasers with amines and, therefore, avoid including both ingredients in any formulation.
Of the three main preservative categories, just isothiazolinones remain. Although this preservative category—which includes methylchloroisothiazolinone and methylisothiazolinone—is considered noncarcinogenic, a segment of the public has demanded isothiazolinone–free skin care products because of the ingredient’s status as “one of the most frequent causes of preservative contact allergy.”14
Considering the alternatives
Given the concerns surrounding traditional preservatives, skin care product manufacturers have looked to alternative ingredients. This has given rise to synthetic preservatives, such as phenoxyethanol, which has actually encountered its own share of controversy, as well as natural preservative blends that utilize essential oils, organic acids and plant extracts. Phenoxyethanol is a synthetic preservative that is often used as a replacement for parabens in cosmetic products. While it is generally safe for use, some individuals may experience side effects, including dermatitis or a worsening of eczema. While some studies have shown that, in high doses, phenoxyethanol can cause depression of the central nervous system, there is no conclusive research regarding this statement. The amount used in cosmetic ingredients, including skin care, is just a very small fraction of that used in the published research. Therefore, for most individuals, the potential for risk from phenoxyethanol exposure is minimal.
Preservatives for Cosmetics is updated with new chapters including regulatory and controversial parabens. If you are interested in cosmetic preservatives, order the book from Alluredbooks.