The parabens, methyl-, propyl-, and parahydroxybenzoate, are the most commonly used preservatives in the United States. An estimated 75 to 90 percent of cosmetics parabens including shampoos, make-up, lotions, and deodorants baby lotions, and sunscreens contain parabens. Water is the only ingredient used more frequently in cosmetics. The parabens have a broad spectrum of antimicrobial activity, were believed to be safe to use, they are relatively nonirritating, nonsensitizing, and nonpoisonous-are stable in acidic or alkaline cosmetics, and are sufficiently soluble in water to be effective in liquids. The typical paraben preservative system contains 0.2 percent methyl- and 0.1 percent propylparaben. In 2004, there was a blip in concern, when a study published in the Journal of Applied Toxicology reported parabens may play a part in breast cancer. British researchers found traces of it in 20 women who had breast tumors. The parabens are believed to act like the female hormone estrogen. There were a number of earlier reports in the scientific literature that expressed concern at the connection between parabens and breast cancer, particularly in underarm deodorants. British researcher, Dr. P.W Harvey, for example, noted in the Journal of Applied Toxicology a year earlier,it was interesting certain parabens lacked activity when swallowed but were clearly active on the skin. Harvey wrote:"This was of "some relevance to the use of underarm cosmetics." He called for further work to establish whether or not the use of underarm cosmetics (particularly containing estrogenic formulas) contributes to the rising incidence of breast cancer. It would seem prudent to conduct this work because the current database is sparse and the effects of long-term low-level exposures to weakly estrogenic chemicals on human health, particularly their application to the underarm and the risks of breast cancer, are unknown.
What about men? It was previously shown that exposure of post-weaning rats and mice to butyl or propyl parabens adversely affects the secretion of testosterone and the function of the male reproductive system. In a study of mice by researchers at the Tokyo Metropolitan Institute of Public Health last November in Food and Chemical Toxicology ( 42(11):1845-9, it was reported that methyl and ethyl parabens do not adversely affect the secretion of sex hormones or the male rats' reproductive function.
The Canadian Department of Health has put parabens on its "Hot list". If a hotlist chemical appears on a label, it is flagged in Health Canada's Cosmetic Notification System (CNS) and the manufacturer is sent a letter of "Canadian Cosmetics Safety Programme's (cq) concern".
The connection between the estrogenic effects of the parabens and humans has faded from press attention today. Since parabens are so widely used in cosmetics, should you be concerned?
While there is no evidence that parabens directly cause cancer, Harvey pointed out in 2004: The hypothesis that underarm cosmetics may contribute to the incidence of breast cancer has obvious implications, not least because of the size of the population potentially exposed… The use of underarm cosmetics presents a special case because of the direct application of the compounds to skin."