Walk into any organic market or high-end cosmetics store and you'll find shelves stocked with alternative deodorants, many of them loudly advertising that they're aluminum free.
This, of course, raises an important body odor question: Did all the deodorants you've been rubbing into your pits until this point contain aluminum, and did that impair your health in any way?
The answer (unless you're allergic to aluminum) is an emphatic no. All the major research into aluminum antiperspirants since the early 2000s has suggested that they're not a problem, according to Dr. Susan Massick, a dermatologist at The Ohio State University Wexner Medical Center.
"The claim that aluminum-containing antiperspirants cause cancer is a myth that has been debunked in the minds of doctors and scientists," she said. [7 Ways Air Pollution Can Harm Your Health]
The idea that antiperspirants with aluminum could be linked to cancer dates back to studies like this one from the early 2000s, showing that if you apply a lot of Old Spice to some cells in a petri dish, those cells suffer DNA damage. Some researchers suggested that the aluminum in the deodorant might be the culprit, and that aluminum-bearing deodorants might be causing breast cancer in women. The main bit of evidence offered for the supposed link? Breast cancer seems more likely to turn up close to the armpit than far away from it.
The problem with this line of thinking is that there are lots of things that cause DNA damage to individual cells in petri dishes that don't actually cause cancer in humans. Dunking some loose cells in a heavy chemical bath is a decent first step if you want to know whether a chemical might be dangerous. But all that sort of study can tell you is whether the chemical is worth studying further, not whether it's actually a problem the way humans use it.
To get to the bottom of the issue, scientists took a deep dive into the world of antiperspirants. Their results thoroughly debunked the idea that women who use aluminum-based antiperspirants get breast cancer more often than those who don't, Massick told Live Science. She pointed to this paper, published in the journal Critical Reviews in Toxicology in 2014, which carefully examined all the existing research into health issues surrounding aluminum and found no evidence that antiperspirant poses any particular danger to human health.
Deodorant makers put aluminum in their formulas, Massick explained, because it blocks the sweat ducts but doesn't penetrate deeper into the skin. That makes it an effective antiperspirant. [7 Ways Alcohol Affects Your Health]
"For a compound to cause cancer," she said, "a mechanism would likely be related to absorption into the bloodstream at a concentration high enough to cause toxicity, and that is not likely with a topical compound applied only to the [armpit]."
In other words, for the chemical to cause cancer it has to actually enter the body in high doses. A small daily dab of aluminum to the armpit just doesn't do that.
To really purge aluminum from the body, you'd have to get rid of more than just deodorant. Marijuana and tobacco contain aluminum, the researchers said in that 2014 review. And, of course, it's present in aluminum foil and in cookware.
The people who actually are at risk for aluminum-related cancers, the researchers found, are industrial workers at smelters and other plants, where there's a high concentration of aluminum-laced dust in the air. But that's a different situation from dabbing a gel onto skin.
"Our skin is the mighty barrier to the outside world," Massick said, so it keeps us safe.
The real exception, she said, are patients with allergies or who otherwise find regular antiperspirants irritating.
"For these patients I would recommend alternative options, such as glycopyrrolate ... and Botox injections [to block sweating]," she said.
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Originally published on Live Science.