09:00 24 January 04
Exclusive from New Scientist Print Edition.
Frequent underarm shaving combined with deodorant use might increase women’s chances of getting breast cancer, claims a study based on a survey of over 400 women with breast cancer in the US. It is the first evidence of such a link to appear in a peer-reviewed journal, but it is far from conclusive.
Claims that deodorants cause breast cancer hit the headlines recently when Phillipa Darbre of the University of Reading in the UK published a paper reporting that preservatives used in antiperspirants and deodorants can be found in breast tumours. But this in no way proved that the preservatives, called para-hydroxybenzoic acids or parabens, actually caused the tumours, and most deodorants no longer contain any parabens.
The US study, by Chicago doctor Kris McGrath of Northwestern University, does suggest that deodorants or antiperspirants might be linked with breast cancer, but only together with underarm shaving. And it has too many weaknesses to be regarded as definitive.
The issue first gained publicity in the 1990s when a hoax email was widely circulated. It claimed that underarm shaving creates tiny nicks, allowing unnamed chemicals from deodorants or antiperspirants to enter the body and trigger tumours.
The first, and until now only, epidemiological study was published in 2002. Dana Mirick’s team at the Fred Hutchinson Cancer Research Center in Seattle included questions on underarm shaving and deodorant use in a study comparing 800 women with breast cancer with 800 randomly chosen women of similar age. Mirick found no evidence of any link.
McGrath’s study, published in December, was smaller. He divided 437 breast cancer patients into four groups depending on how often they shaved and applied deodorant. He found that the more zealous the underarm regime, the younger the women were when diagnosed with cancer.
Those who shaved at least three times a week and applied deodorant at least twice a week were almost 15 years younger when diagnosed than women who did neither (European Journal of Cancer Prevention, vol 12, p 479).
Neither shaving nor deodorant use alone was linked with a younger age of diagnosis. McGrath suspects the aluminium compounds found in many products might be to blame.
But Mirick says McGrath’s study has major limitations. The most serious is the absence of a control group without breast cancer, she says. That means there could be a simple explanation for the findings: younger women use antiperspirant and shave more often than older women.
McGrath admits that the study’s power is limited. But he claims it is the first to address the intensity of underarm hygiene regimes. “If a disease is from a lifestyle, those exposed to that lifestyle more should have an earlier diagnosis than those less exposed. For example, the more one consumes alcohol the sooner an alcohol-related disease should appear,” McGrath says.
“It is a landmark publication because it provides the first epidemiological evidence for a link between the use of antiperspirants/deodorants and breast cancer development,” claims Darbre.
Like Darbre, McGrath speculates that the steady rise in the incidence of breast cancers could be linked to deodorants. But in fact the rise in underarm deodorant use seems to parallel or even lag slightly behind the cancer rise, says David Philips of the Institute of Cancer Research in London – the opposite of what you would expect if there was a link.
Darbre cites as another cause for concern the fact that over half of breast cancers occur in the part of the breast nearest the armpit. But sceptics say this is because that quadrant has the largest amount of breast tissue.
Mirick’s work has convinced most experts that there is nothing to worry about. But McGrath and Darbre argue that their studies provide enough evidence to justify funding bigger and better studies.
Journal reference: European Journal of Cancer Prevention (vol 12, p 479)
Source: New Scientist, online at www.NewScientist.com