Dear Doctor: I know that doctors say there's no connection between breast cancer and deodorants/antiperspirants. But has this ever been tested?
Dear Reader: First, we should explain the difference between deodorants and antiperspirants because each has chemicals that cause concern. Deodorants, as the name implies, remove the odor from axillary (underarm) sweat by killing, or stopping the growth of, bacteria. Antiperspirants decrease the amount of sweat excreted by sweat glands. Stick and roll-on products often contain a combination of deodorant and antiperspirant, and their wide use is intertwined with modern living -- they remove the pungent odors that can act as barriers to human interaction.
More than 50 percent of breast cancers occur in the upper outer quadrants of the breast, near the underarm. The concern many people have is that chemicals applied to the underarm may find their way to the breast tissue. The thinking goes like this: Because many breast cancers are stimulated by estrogen -- and underarm products often contain estrogenlike chemicals -- such products may stimulate breast cancers.
It's true that deodorants contain phenol compounds, such as triclosan, which have estrogenlike properties, and antiperspirants often contain aluminum, which activates estrogen receptors. Further, the parabens used as preservatives in underarm products also have estrogenlike properties.
Lastly, aluminum chloride and aluminum chlorohydrate, which are often found in antiperspirants, have been shown to decrease BCRA-1 gene function in the breast and also decrease many of the repair genes within the breast. This could increase susceptibility to breast cancer -- again, so the thinking goes.
But do all these factors add up to actual risk? A 2002 study looked at 813 women diagnosed with breast cancer between 1992 and 1995 and compared them with 793 women without breast cancer. The authors asked the women whether they had used deodorant/antiperspirants -- and if so, how regularly -- and whether they had used the products within one hour after shaving. Some people suspect that shaving creates minute cuts in the skin that allow the underarm products to do more damage. The authors found no difference in the rates of underarm-product use between those who had breast cancer and those who didn't.
Another study, this one in 2003, asked 437 women diagnosed with breast cancer about their antiperspirant/deodorant use and underarm shaving. Those who shaved and used underarm products the most were diagnosed with breast cancer 12.6 years earlier on average than those who did this infrequently. Those women who began shaving and using underarm products before the age of 16 had a diagnosis of breast cancer 9.6 years earlier than those who began this practice after age 16.
Note, however, that both studies were retrospective, meaning that they looked back after the disease had already occurred. What would be more convincing is a prospective study -- with similar populations of people who use and don't use underarm products -- that follows participants for many years. An estimated 90 percent of people use antiperspirants/deodorants in the United States, so a prospective type of study may finally lay to rest the link between underarm products and breast cancer.
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