The idea of such a connection has been floating around for years, but appears meritless.
The theory had been that women were putting themselves at risk by applying deodorants or antiperspirants within a short time of shaving their armpits, thereby introducing chemicals into their bloodstream. But in the best epidemiological study to date, published in 2002 in the Journal of the National Cancer Institute, researchers studying 1,600 women found no link to breast cancer, with either antiperspirants, which limit perspiration, or deodorants, which suppress odor.
The National Cancer Institute says on its website http://cis.nci.nih.gov/fact/3 66.htm that “there is no conclusive research linking the use of underarm antiperspirants or deodorants and the subsequent development of breast cancer.”
That doesn’t totally settle things, however. In 2003, a study in the European Journal of Cancer Prevention of 437 women who had had breast cancer found that the age of diagnosis was earlier in women who had used deodorants or antiperspirants and who shaved under their arms more frequently than those who did not. This study is inconclusive for several reasons, including the fact that there was no control group of women without cancer.
Some toxicology studies have also hinted at a potential link. One 2004 study in the Journal of Applied Toxicology looked at 20 samples of breast tumors and found preservatives used in underarm cosmetics. But, the study was flawed and did not directly link deodorant or antiperspirant use to the preservatives, said Dr. Kala Visvanathan, a cancer specialist at the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins.
“I don’t think there is reason to be greatly concerned,” said Dr. Eric Winer, director of the breast oncology center at Dana-Farber Cancer Institute. “In the absence of additional research, I would encourage a friend to put this out of her mind.”