Parabens – friend or foe?

Propylparaben

Propylparaben is the ester form of p-hydroxybenzoic acid that has been esterified with n-propanol. It is the most commonly used antimicrobial preservative in foods, cosmetics, and drugs. It is readily absorbed through the skin and GI tract. It is quickly hydrolyzed and excreted in the urine and does not accumulate in the body.

Estrogenic activity of parabens

Dr. Leslie S. Baumann

In a 2004 study, Darbre et al. reported on the discovery of parabens-like substances in breast tissue and published these findings in the Journal of Applied Toxicology.¹⁰ The media and public panicked, saying that parabens have estrogenic activity and can cause breast cancer. However, many studies have shown that certain parabens do not have estrogenic activity. Although some parabens have been shown to impart estrogenic effects in vitro, these are very weak. The four most commonly used parabens in cosmetic products are 10,000-fold or less potent than 17beta-estradiol.¹¹ The potential to result in an adverse effect mediated via an estrogen mode of action has not been established in humans.⁶ Paraben exposure differs geographically. No correlation has been found between the amount of parabens in a geographic location and the incidence of breast cancer. Current scientific knowledge is insufficient to demonstrate a clear cancer risk caused by the topical application of cosmetics that contain parabens on normal intact skin.¹¹

Parabens and contact dermatitis

Paraben compounds are capable of minimal penetrance through intact skin.¹² When they are able to penetrate the skin – a capacity that varies among the class – parabens are rapidly metabolized to p-hydroxybenzoic acid and promptly excreted in the urine.^3,11 Parabens for many years were thought to cause contact dermatitis, and there are many reports of this. However, the incidence is much lower than previously thought. In fact, parabens were named “Nonallergen of the Year in 2018” because of the low incidence of reactions in patch tests.¹³ Higher concentrations of parabens applied topically to skin – especially “nonintact” skin – have been shown to cause mild irritant reactions. It is likely that many of these reported cases of “contact dermatitis” were actually irritant dermatitis. Longstanding concerns about the allergenicity of parabens in relation to the skin have been rendered insignificant, as the wealth of evidence reveals little to no support for the cutaneous toxicity of these substances.¹¹ Yim et al. add that parabens remain far less sensitizing than agents newly introduced for use in personal care products.⁴

Daily average exposure to parabens

It is estimated that parabens are found in 10% of personal care products. In most cases, these products contain 1% or less of parabens. If the average patient uses 50 g of personal care products a day, then the average daily exposure to parabens topically is 0.05 g. Parabens also are found in food and drugs, so the total paraben exposure per day is assumed to be about 1 mg/day. (See the 2002 Food and Chemical Toxicology article for details of how this was calculated.)⁷ When food, personal care products, and drug exposure rates are added, the average person is exposed to 1.29 mg/kg per day or 77.5 mg/day for a 60-kg individual. You can see that personal care products account for a fraction of exposure, as most paraben exposure comes from food.