 A famous case report called the Mortician's Mystery in the New England Journal of Medicine back in the 80s described a man whose testicles started shrinking and breasts started growing. Turns out he failed to wear gloves as he massaged embalming cream onto his corpse. They conclude there must have been some estrogenic compound in the cream that got absorbed through his skin into his body, one of the first such cases described. This case was cited as inspiration by a group of researchers that came up with a new theory to explain a breast cancer mystery. Why do most breast cancers occur in the upper outer corner of the breast? The standard explanation was simply because that's where most of the breast tissue is located, as the so-called tail of the breast extends up into the armpit. But that doesn't explain this. It didn't always used to be that way. There's been a shift towards that upper corner. And it doesn't explain this. Greater genomic instability, chromosome abnormalities that may signal pre-cancerous changes. There definitely seems to be something happening to that side of the breast. And something relatively new, just in the last 50 years or so, is it possible that the increasing use of underarm antiperspirant, which parallels increasing breast cancer incidents, could be an explanation for the greater number of tumors and the disproportionate incidence of breast cancer in the upper outer quadrant of the breast near where the stick sprayer roll-on is applied. There's a free flow of lymph fluid back and forth between the breast and the armpit, and if you measure aluminum levels in breasts removed after mastectomies, the aluminum content of breast tissue in the outer regions near the armpits was significantly higher, presumably due to closer proximity to the underarm region. This is a concern, because in a Petri dish at least, it has been demonstrated that aluminum is a so-called metalloestrogen, having proestrogenic effects on breast cancer cells. Long-term exposure of normal breast tissue cells in a test tube to aluminum concentrations in the range of those found in the breast results in pre-cancerous type changes. And then once the cells have turned, those same concentrations can increase the migratory and invasive activity of human breast cancer cells in a Petri dish. This is important because women don't die from the tumor in the breast itself, but from the ability of the cancer cells to spread and grow at distant sites like the bones, lungs, liver, or brain. But we don't care about Petri dishes, we care about people. In 2002, a paper was published in the Journal of the National Cancer Institute, in which the underarm antiperspirant habits of 800 breast cancer survivors was compared to women who never got breast cancer, the first study of its kind, and they found no indication of a link between the two. Based on this study, Harvard Women's Health Watch assured women that antiperspirants do not cause breast cancer. Women who are worried that antiperspirants might cause breast cancer can finally rest easy. But two months later, this study. Frequency and early onset of antiperspirant deodorant usage with underarm shaving was associated with an earlier age of breast cancer diagnosis as much as 20 years earlier. In women using antiperspirant and shaving their armpits more than three times a week, and the earlier they started before versus after their sweet 16, appeared to move up their breast cancer 10 or 20 years. They conclude that underarm shaving with antiperspirant use may play a role in breast cancer after all. But what does shaving have to do with it? Shaving removes more than just armpit hair. It removes armpit skin. You end up shaving off the top skin layer. And while there's very little aluminum absorption through intact skin, when you strip off that outer layer with a razor and then rub on some antiperspirant, you get a six-fold increase in aluminum absorption through the skin. So good news for women who don't shave, but on the other hand, the high through-the-skin aluminum uptake on shaved skin should compel antiperspirant manufacturers to proceed with the utmost caution. European safety authorities and the FDA specifically advise against using aluminum antiperspirants on damaged or broken skin, yet shaving before antiperspirant application can create abrasions in the skin. I'm sure everyone knows about the FDA warning having read Title 21, Part 350, subpart C50-5C1 of the Code of Federal Regulations. But we get so much aluminum in our diet from processed foods, anti-caking agents in like pancake mix, melting agents in American cheese, meat binders, gravy thickeners, baking powder, candy. That the contribution from underarm antiperspirants would presumably be minimal in comparison, but everything was turned topsy-turvy in 2004 when a case was reported of a woman with bone pain and fatigue suffering from aluminum toxicity. But within months of stopping the antiperspirant, which she was applying daily to her regularly shaved pits, her aluminum levels came down and her symptoms resolved. Although not everyone sucks up that much aluminum, the case suggests that caution should be exercised when using aluminum containing antiperspirants frequently. Recently, it was shown that women with breast cancer have twice the level of aluminum in their breasts compared to women without breast cancer, though this doesn't prove cause and effect. Maybe the aluminum contributed to the cancer, or maybe the cancer contributed to the aluminum. Maybe tumors just suck up more aluminum? Subsequent research suggests this alternative explanation is unlikely. So where do we stand now? The latest review on the subject concluded that as a consequence of the new data, given that aluminum can be toxic and we have no need for the stuff, reducing the concentration of this metal in antiperspirants is a matter of urgency. Or at the very least, it should say on the label, do not use after shaving. Or we could cease usage of aluminum containing antiperspirants altogether, but then won't we stink? Ironically, antiperspirants can make us stink worse. They increase the types of bacteria that cause body odor. It's like the story with antidepressant drugs, how they can actually make you more depressed in the long run. The more we use antiperspirants, the more we may need them. Awfully convenient for a billion-dollar industry.