Authors: Dr. ZITOUT Amira Hania, Dr. DAOUD Lamia, Dr. BOUMARAF Khawla
Seven thirty in the morning, in the bathroom. A gesture performed without a second thought since adolescence: the antiperspirant, applied in a second, tossed back in the bag, forgotten just as quickly. And yet, for the past twenty years or so, this small ritual has fed a persistent worry: what if the aluminum salts it contains were not entirely risk-free for the breast? A review of the scientific literature sorts out what is established from what remains uncertain.
This article was contributed by the Algerian Society of Cosmetology.
An Unremarkable Ritual
In the bathroom, the antiperspirant is one of those products we no longer really notice. Yet it performs a precise task. Its aluminum salts (aluminum chlorohydrate, aluminum-zirconium complexes) form a temporary plug at the opening of the sweat glands, thereby reducing perspiration.
It is this very regularity that caught researchers’ attention. A product applied every day, for decades, just a few centimeters from the breast: the question of cumulative exposure arose naturally.
Aluminum Salts and Breast Cancer: The Association Making Headlines
Breast cancer is the most common cancer among women: according to World Health Organization (WHO) data, about 2.3 million new cases were recorded worldwide in 2022. In Algeria, the National Network of Cancer Registries (RNRC) reports more than 14,000 new cases in 2023.
A significant proportion of tumors occur in the upper outer area of the breast, close to the armpit — precisely where these products are applied.
This proximity was enough to give rise to a hypothesis. But a hypothesis is not proof. To find out what actually holds up, a literature review conducted at the Faculty of Pharmacy in Algiers (as part of a master’s degree in cosmetology and dermopharmacy) examined 23 scientific studies.
In the Lab, Signals Worth Raising an Eyebrow Over
First level: the test tube. Human breast cells, cultured in the laboratory, were exposed to aluminum salts. The observations are attention-grabbing. Under these conditions, aluminum appears to inhibit proteins responsible for repairing DNA, including BRCA1 and Rad51. It also seems to partly mimic the action of estrogens — the hormones that fuel the growth of many breast cancers — which has earned it the label “metalloestrogen.” Finally, exposed cells move faster and lose some of their natural restraint on multiplication.
Striking? Yes. But these experiments take place on isolated cells, with no skin to protect them, no immune system, and none of the body’s natural filters. These results alone are not enough to conclude that the aluminum in antiperspirants produces the same effects inside a human body.
From Bottle to Breast: Aluminum on the Trail
Second level: tissue. Analyses have detected aluminum in breast tissue, in fluid drawn from the nipple, and in fluid from certain breast cysts. One striking detail: it appears to concentrate more heavily in the outer part of the breast, on the armpit side.
Another piece of the puzzle: in laboratory tests on human skin samples, freshly shaved skin lets through more aluminum than intact skin — a plausible clue as to how it might cross the skin barrier, though for now this remains strictly a laboratory observation.
But aluminum is ubiquitous in our environment. It is also found in healthy tissue, and results diverge when diseased and healthy tissue are compared. Its mere presence therefore tells us neither where it came from nor whether it plays any role in the disease.
Among Women, the Story Gets Blurry
What matters most remains: what actually happens in women themselves? Only three of the 23 studies address this question — and they do not tell the same story.
The first compares 209 women with breast cancer to 209 women without the disease. It finds a higher risk among those who reported using these products several times a day before age 30. The figure often cited — roughly four times higher — is striking, but highly imprecise: the statistical range runs from barely any increase in risk to nearly fifteen times higher. It also applies to a very narrow subgroup.
The second, involving 437 patients, found that those reporting the most frequent use (combined with shaving) were diagnosed earlier: 52.6 years old on average, versus 67.3 years for non-users. But it includes only women who were already ill, with no comparison group, so it cannot establish a cause.
The third, with 384 patients and 384 healthy women, found no difference at all: roughly the same proportion of users in both groups.
Why the Answer Keeps Slipping Away
Each level of evidence has its own blind spots.
In the lab, conditions are far removed from real life. What’s more, striking results tend to get published more often than null results, which can distort the overall picture.
In tissue, it’s impossible to know whether the aluminum was there before the disease or whether it accumulates in tissue already affected. The upper outer area of the breast is also richer in glandular tissue, which could explain both the frequency of tumors there and the buildup of substances, independent of anything applied under the arms. And since aluminum is everywhere, contamination during analysis is easy to introduce.
Among women, the data rely on questionnaires: participants must recall habits from twenty or thirty years earlier, and people who are ill may remember their past differently. The study groups are small, and other factors — age, lifestyle habits — further cloud the picture.
What This Means for the Cosmetics Industry
Major institutions remain cautious. In the United States, the National Cancer Institute and the American Cancer Society consider that current knowledge does not support establishing a cause-and-effect link. In Europe, the Scientific Committee on Consumer Safety regards aluminum as safe for cosmetic use, provided strict limits are respected: 6.25% for non-spray products (roll-ons, sticks) and 10.60% for sprays.
All of these institutions acknowledge that further research is still needed into long-term use, absorption through the skin, and the underlying biological mechanisms.
On store shelves, the “aluminum-free” trend has obvious appeal. These findings alone do not support the conclusion that an aluminum-free deodorant is safer, nor that a conventional antiperspirant is dangerous. These are two products with different functions: one limits perspiration, the other targets odor.
The Advice Worth Remembering
None of this is cause for panic, nor a reason to throw out your antiperspirant. If you’d rather err on the side of caution, aluminum-free alternatives do exist — as long as you accept that they won’t stop perspiration itself. To check a product’s composition, look on the label for aluminum-based ingredient names, such as aluminum chlorohydrate. If you have personal concerns, your pharmacist or doctor remains the best person to talk to.
What the Science Tells Us
Main finding: current evidence does not support establishing a cause-and-effect link between aluminum-based antiperspirants and breast cancer. The signals observed in the lab are not consistently reproduced in women.
What was reviewed: 23 studies, including about ten on human cells, about ten on tissue, fluids, and product composition, and only 3 involving women (209 cases and 209 controls; 437 patients; 384 cases and 384 controls).
Method: systematic literature review (PubMed, Cochrane Library, Google Scholar), study selection following the PRISMA 2020 method by two independent reviewers, qualitative synthesis without combined statistical analysis.
Main results: in the lab, effects on DNA repair, hormonal activity, and cell behavior. In tissue, presence of aluminum, notably on the armpit side, with inconsistent differences between diseased and healthy tissue. In women, contradictory results.
What can actually be concluded: the question remains open — neither proven nor ruled out. Large, long-term studies following women over many years, with objective measurement of exposure, are still lacking.
Beauty: What Does This Change?
Consumers: no reason to be alarmed based on this data. Choosing an aluminum-free product is a matter of personal precaution, not a demonstrated safety benefit.
Brands: this research does not support claiming that an “aluminum-free” product is safer. Honest communication should keep a product’s actual function (odor control versus perspiration control) separate from any health claim.
Formulators: the European limits (6.25% and 10.60%) remain the reference framework. The open questions concern skin absorption and cumulative exposure.
Pharmacists and dermatologists: an educational role to play — explaining the difference between a laboratory signal, a presence in tissue, and a demonstrated risk in humans.
Cosmetics industry: the need for high-quality studies, using objective measurement of exposure rather than questionnaires, is a matter of credibility for the entire sector.
Conclusion
The morning ritual hasn’t changed: a quick pass under each arm, and the day begins. What has changed is the way we look at it. The science of beauty isn’t about handing down verdicts, but about being able to say clearly what has been demonstrated, what is plausible, and what remains unknown. When it comes to the aluminum in antiperspirants, the science is still being written. Between the test tube and the bathroom sink lies an entire human body — and that is where the next answers will have to be found.
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