The primary focus of Nature’s Pulchritude is to educate. This post is the fourth in a series of in depth posts that will educate you about the various preservatives in hair and skin products, as well as their potential toxicity.
Preservatives are added to cosmetics, personal care products, and food to maintain a products integrity and stability by inhibiting or reducing the growth of microorganisms such as bacteria and fungus (FDA). Most products sold via retail sit for extended periods of time during shipping, in a warehouse, and on store shelfs that allow enough time for a product to spoil or cause microbial growth which render the product unfit for use. This is particularly true for products that contain water, such as many conditioners and moisturizers, and other active ingredients (antioxidants and emulsifiers) that would otherwise lose their effectiveness and stability over time.
Preservatives are chosen in cosmetics based on a variety of factors which include ability to inhibit growth over a broad spectrum and method of derivation (natural vs. synthetic). Preservatives tend to be in concentrations less than 2% of the weight of the formula, however, widespread use of potentially harmful preservatives, such as parabens, has been a great cause of concern for some scientists and consumers. The Food, Drug, and Cosmetic Act does not grant the Food & Drug Administration the authority to regulate the use of preservatives unless it is known to be “poisonous or deleterious” (FDA).
Potassium Sorbate is the potassium salt (neutralization reaction of an acid and a base) of sorbic acid. It is created by using potassium hydroxide (KOH) to neutralize sorbic acid (C6H8O2). Sorbic acid is naturally occurring in the rowan berry, however, it is primarily produced synthetically. Potassium Sorbate (C6H7KO2) is a common food and wine preservative that is used to inhibit the growth of mold and yeast, and is also used in various personal care products. Potassium sorbate has been regarded as a safe replacement for parabens in cosmetics and personal care products. Potassium sorbate is believed to have a long safety record, though it can be a cause of concern. Use of sorbic acids and its salts (potassium sorbate) are limited to 0.6% by the EU.
Potassium sorbate was found in 9% of 204 tested cosmetics products (92 shampoos, 61 conditioners, 34 liquid soaps, and 17 wet tissues), making it the 12th most abundant preservative detected (Yazar et al. 2010). Potassium sorbate is considered generally safe by the FDA, and has been found to be relatively non-toxic. A study conducted in 1990 found potassium sorbate to show “a very low level of mammalian toxic,” even at up to 10% of the diet, devoid of carcinogenic activity, and non-mutagenic in in vitro and in vivo tests (Walker 1990). Potassium sorbate is also considered a nonirritant to the eyes and only slightly irritating to the skin. In contrast, a 1992 study found potassium sorbate to be a low-level mutagen, which supported studies from 1977 that found similar results in in vitro hamster cells (Würgler et. al 1992). Additionally, 2010 study found potassium sorbate to be genotoxic to human peripheral (close to surface) blood lymphocytes (white blood cell) in vitro, causing damage to DNA (Mamur et al. 2010).
Potassium sorbate is considered one of the safest synthetic preservatives used in cosmetics. By and large, potassium sorbate is regarded as generally safe, is not a carcinogen and has relatively low toxicity and mutagenic activity. As of 2006, the Cosmetic Ingredient Review lists potassium sorbate as safe for use in cosmetics and did not find it to be mutagenic within accepted guidelines (0.00003% – 0.7%) (CFTA 2006; CIR 2008). It is a prevalent preservative in food as compared to cosmetics. Only one of the papers specifically researched potassium sorbate in cosmetics, and that paper did not go into detail about deleterious effects of it as a preservative. Additional research should be done on the toxicity of potassium sorbate in cosmetics and personal care products. There is a chance that dermal exposure could be just as or more harmful than oral exposure, but there is presently no information to support that possibility.
Cosmetic Ingredient Review. 2008. “Annual review of cosmetic ingredient safety assessments: 2005/2006.” International Journal of Toxicology. 27(Supp. 1): 77-142.
Mamar,S., Yüzbaşıoğlu, D., Ünal, F., and S. Yılmaz. 2010. “Does potassium sorbate induce genotoxic or mutagenic effects in lymphocytes?” Toxicology in Vitro. 24(3): 790-794.
Yazar, K., Johnsson, S., Lind, M., Boman, A., and C. Liden. 2010. “Preservatives and fragrance in selected consumer-available cosmetics and detergents.” Contact Dermatitis. 64: 265-272.
Walker, R. 1990. “Toxicology of sorbic acid and sorbates.” Food Additives and Contaminants. 7(5): 671-676.
Würgler, F.E., Schlatter K., and P. Maier. 1992. “The genotoxicity status of sorbic acid, potassium sorbate and sodium sorbate.” Mutation Research. 283: 107-111.