The truth: The American Cancer Society says, "There is no proof that the use of antiperspirants or deodorants causes breast cancer." In fact, one study debunks this widely spread Internet myth. Researchers in Seattle studied 813 women who were first diagnosed with breast cancer from 1992 to 1995 and then compared them to 793 women without the disease. Whether the women used antiperspirants or deodorants, whether they shaved with a blade razor or used another form of underarm hair removal, there was no evidence of a link to the risk of breast cancer. The study was published in the Journal of the National Cancer Institute (Vol. 94, No. 20: 1578-1580).

You can read more about the study on the American Cancer Society Website.