What is the rate of ACD with parabens?
One of the main reasons that parabens were designated as the ACDS nonallergen of the year is the very low rate of ACD associated with parabens. The North American Contact Dermatitis Group, a research group with members in the United States and Canada, reported a 0.6% positive reaction rate when patch testing with paraben mix 12%,7 which closely compares with a 0.8% positive reaction rate when patch testing with paraben mix 16% using the Mayo Clinic standard series.8 From the standpoint of ACD, this very low patch test reaction rate makes parabens one of the safest preservative options for use in cosmetic products.
Are there health risks associated with parabens?
The paraben controversy in the scientific literature and in the lay press centers around potential health risks and endocrine disruption. We will focus on the conversation regarding parabens and the risk for endocrine disruption and association with breast cancer.
Parabens have been reported to have estrogenic effects; however, the bulk of the data is limited to in vitro and animal studies, with less evidence of endocrine disruption in humans.2 In vitro studies have demonstrated that the estrogenic potency of parabens is much less than that of estrogen. In one study, parabens were shown to be 10,000-fold less potent than 17β-estradiol9; in a separate study, they had a maximum potency of only 1/4000 that of estrogen.10 Additionally, an in vitro study showed varying ability for parabens to bind estrogen receptors, with a greater ability to bind with longer alkyl side chains.11 The result is decreased or increased estrogen activity, dependent on side chain length and type of receptor.2 Finally, some studies add conflicting results that parabens may actually create an antiestrogenic effect in human breast cancer cells.12 From the standpoint of estrogen mimicry, there are no known studies in humans confirming harmful effects associated with paraben exposure.
The reported association between parabens and breast cancer is closely related to their theoretical estrogenic effects. The conversation regarding parabens and breast cancer has been fueled by the identification of parabens in human breast tumors and their presence in concentrations similar to what is needed to stimulate in vitro breast cancer cells.2 The existing data do not confirm causation. An association with parabens in topical axillary personal care products has been theorized but not confirmed; for example, it was shown that paraben levels were highest in the axillary region of breast cancer tissue, including women who had never used deodorant. It was concluded that the presence of axillary parabens was due to sources other than topical axillary personal care products.13 Another study confirmed there was not an increased risk for breast cancer in patients who applied personal care products to the axillary area within an hour of shaving.14 The existing data do not support topical paraben exposure as a risk for breast cancer.
Final Thoughts
Parabens are preservatives frequently found in personal care products and exhibit a very low rate of associated ACD. Consumers may be exposed to parabens through foods, cosmetics, and medications. Although there have been consumer concerns regarding endocrine disruption or carcinogenicity associated with parabens, definite evidence of their harm is lacking in the scientific literature, and many studies confirm their safety.2 With their high prevalence in personal care products and low rates of associated contact allergy, parabens remain ideal preservative agents.
Ultimately, contact dermatitis is a common yet often underrecognized dermatologic condition. To address this knowledge gap in clinical practice, we are proud to launch Final Interpretation, a new column in Cutis covering emerging trends in contact dermatitis. We will address pearls, pitfalls, and updates in contact dermatitis. Although our primary focus will be ACD, other important causes of contact dermatitis will be highlighted. Look for the inaugural column in the June 2019 issue of Cutis.