The antiperspirant-breast cancer claim has achieved something akin to urban legend status on the Internet and in the popular press, despite that fact that few clinical studies in humans have addressed the issue.
One of the strongest, published in 2002, found no link between antiperspirant or deodorant use and breast cancer risk. Researchers compared usage patterns among roughly 800 breast cancer patients and a similar number of women without the disease.
Easing Women's Fears
Biostatistician Dana Mirick, MS, who led the study, says the findings should ease women's fears.
"I think that the people who do this type of research consider the matter closed," she tells WebMD.
But cancer researcher Philippa Darbre, PhD, of the University of Reading in England, sees it differently. She says the evidence is mounting that the aluminum-based active ingredient in antiperspirants can mimic estrogen in the body.
"Lifetime exposure to estrogen is the risk factor which is tied most strongly to breast cancer," Darbre tells WebMD. "If the aluminum salts in antiperspirants enter the body and mimic estrogen it stands to reason that constant exposure over many years may pose a risk."
Risks Of Aluminum Exposure?
Aluminum salts are the active ingredient in the vast majority of antiperspirants, and antiperspirants are a major source of exposure to aluminum in humans.
Products labeled as deodorants alone may not have aluminum, but the vast majority of commercially available antiperspirants do contain aluminum salts. They make up as much as a quarter of the volume of some antiperspirants.
Darbre says her own cellular research shows that aluminum salt exposure can influence estrogen activity. Because antiperspirants are used so closely to the breast, and are often used by women directly after shaving — which might allow for easier absorption — she says it is reasonable to question whether antiperspirant exposure could influence breast cancer risk.
She adds that women should consider cutting down on their antiperspirant use or cutting them out entirely.
"If a product is labeled antiperspirant it probably contains aluminum salts," she says. "I stopped using these products eight years ago, and now I wonder why I ever bothered. Soap and water and maybe a little talcum powder seem to do the job nicely."
She acknowledges, however, that cellular studies fall far short of proving that regular use of antiperspirants poses any kind of cancer risk.
In earlier studies she found that preservatives commonly found in antiperspirants and other cosmetics, known as parabens, may also influence breast cancer risk by mimicking estrogen. Other studies show that the metal cadmium, found in the environment and a component of cigarette smoke, does the same thing.
"Each of these agents on their own may not have a powerful effect, but we need to see what happens when a number of them act together, she says. "It could be that this would have a significant effect on disease like breast cancer."
Cancer Groups Weigh In
In a report released in 2004, officials with the National Cancer Institute concluded that there was "no conclusive research" linking the use of underarm antiperspirants or deodorants to breast cancer.
Likewise, a recently released report from the American Cancer Society concluded that "there is no good scientific evidence to support the claim" that antiperspirants raise a woman's risk of developing breast cancer.
ACS spokeswoman Elizabeth Ward, PhD, tells WebMD that there is not much evidence that any environmental exposure has a big impact on breast cancer risk. She points out that studies examining pesticides known to mimic estrogen have failed to show a link between exposure and breast cancer.
"This is a topic that is still under study, and it is important to study it further," she says. "But no strong evidence has emerged of a relationship [between breast cancer risk] and exposure to environmental contaminants."
A major government study involving 50,000 sisters of women with breast cancer may provide some answers about environmental and genetic causes of the disease.
The 10-year Sister Study, begun in 2004, will be the most detailed study ever to address the question of how environmental exposures, including cosmetic exposures, influence breast cancer risk, she says.
SOURCES: Darbre, P.D. Journal of Applied Toxicology, Feb. 28, 2006, online edition. Philippa Darbre, PhD, senior lecturer in oncology, University of Reading, Reading, U.K. Dana K. Mirick, MS, biostatistician, Fred Hutchinson Cancer Research Center, Seattle. Elizabeth Ward, PhD, director of surveillance research, American Cancer Society.
By Salynn Boyles
Reviewed by Louise Chang, MD
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