My research on this topic - Aluminium Antiperspirants and Breast Cancer Risk, began as a discussion session in one of the conferences I was invited to speak at.

The Story Behind

Transcript

Two common concerns often come up when we talk about deodorants and antiperspirants.

First, does current evidence say that using deodorants causes breast cancer? The answer so far is no.
Second, are aluminium-based antiperspirants safe? To answer this, we need to look at:

• How sweat glands work
• How aluminium functions in antiperspirants
• What research tells us about absorption
• What practical precautions make sense in daily life

Let’s Begin with Sweat, Bacteria and Odour

There are two main types of sweat glands in our skin - eccrine glands and apocrine glands.

• Eccrine glands, or common sweat glands, are found almost everywhere on the body and are active from birth. Their primary job is to cool us down. They produce a watery sweat made mostly of water, salts, small amounts of natural acids, and trace antimicrobial agents. The ducts open directly onto the skin surface through tiny pores.
• Apocrine glands, on the other hand, are seen only in certain areas - the underarms and the groin. They usually become active at puberty. They are larger than eccrine glands, and instead of opening directly into the skin, their ducts open into hair follicles. Their secretion is thicker and more oily, rich in fatty acids, proteins, and steroids, and it mixes with natural skin oils before it reaches the surface.

Interestingly, fresh sweat from both types of glands is actually odourless. The smell happens because of the bacterial action on the sweat itself.

The Underarm Microbiome

Microbiome simply means the complete list of all microorganisms in a given environment. In the underarm setting, the microbiome includes bacteria such as Propionibacterium, Micrococci, Staphylococcus, and Corynebacterium.

Of these, Staphylococcus and Corynebacterium are the biggest odour producers.

• Staphylococcus hominis produces a sulphur compound so potent that our noses can detect it in billionths of a gram.
• Corynebacterium species produce fatty acids with a pungent smell.

Other chemicals, like aldehydes, contribute to the recognisable sharp note of body odour.

So, sweat + bacteria + chemistry = body odour.

Aluminium: The Hero Ingredient in Antiperspirants

Aluminium salts have been the backbone of antiperspirant formulations for more than a century. The first official aluminium based deodorant debuted in 1903, called Everdry.

Since then, many formulations have entered everyday use. If an antiperspirant works well, it most likely contains aluminium. Other agents, such as zirconium or titanium exist, but aluminium does the heavy lifting.

Common forms of aluminium in antiperspirants include:

• Aluminium chloride
• Aluminium chloride hexahydrate (ACH)
• Aluminium chlorohydrate
• Aluminium–zirconium complexes
• Aluminium chlorosesquihydrate (newer, gentler)
• Alum (potassium aluminium sulfate, natural but still an aluminium salt)

Of these, aluminium chloride is the most potent and considered prescription strength, though more irritating.

How Aluminium Works to Reduce Sweating

Here’s the sequence of what happens on your skin when you apply an aluminium antiperspirant:

1. Dissolution – Aluminium salts dissolve in sweat or skin moisture.
2. Reaction – The ions react with electrolytes and proteins in sweat to form an insoluble gel-like precipitate.
3. Plugging – This gel forms a physical plug in the acrosyringium (the opening of the eccrine duct), like a cork in a bottle.
4. Temporary changes – Repeated use causes mild duct swelling, prolonging the effect even after skipping use.
5. Shedding – Plugs are temporary and shed naturally with skin renewal.

By blocking sweat from reaching the surface, aluminium reduces the “fuel” for odour causing bacteria. This is why antiperspirants, unlike deodorants, tackle both sweat and smell.

Strength Matters

The performance of the antiperspirant depends on the concentration of aluminium in your product.

• OTC products: up to ~12.5% aluminium chlorohydrate - enough for daily sweat control with low irritation risk. The exact limit differs from country to country.
• Prescription products: 15–20% aluminium chloride hexahydrate. These form deeper plugs but are more likely to cause skin irritation because of the hydrochloric acid released during the reaction with sweat. This is more common with plain aluminium chloride compared to the more compounded salts, but it can also be due to the plug formation itself.

The Absorption Question

Can aluminium salts from antiperspirants enter the body through the skin?

The first human absorption study we have is from 2001.

• Two volunteers applied radiolabelled aluminium chlorohydrate to their underarms. In other words, tagged aluminium on their underarms, which could be picked up from the blood using special tests - if it did get absorbed.
• What they found was the amount absorbed into the bloodstream was 0.012% of the applied dose - so low that the authors concluded topical aluminium chlorohydrate doesn’t meaningfully add to the body’s aluminium burden.

But things got complicated in 2004, when a case report described a woman with abnormally high blood aluminium and persistent bone pain. She had applied an aluminium antiperspirant daily for four years to freshly shaved underarms - a situation where the shaving could have compromised the skin and that could have led to increased absorption. She was evaluated by doctors who considered her deodorant to be the problem agent, and she was asked to stop using it. And, when she stopped using it, her blood aluminium dropped back to normal, and her symptoms resolved. This was one of the first instances that received wide medical attention, where aluminium from deodorants could actually create trouble for its users.

The Role of Shaving in Aluminium Absorption

Now, another detail comes up when you look closely at the research - When you shave, wax, or use abrasive exfoliators in the underarm area, you don’t just remove hair, you also create microscopic cuts and scrapes in the skin’s surface.

These micro-injuries can weaken the barrier that normally keeps substances out, creating tiny entry points for whatever you apply next. Basically, you have done the shaving, waxing etc, which has opened up the skin, and right after you apply the antiperspirant, which allows the aluminium in the product to enter the skin through the small cuts and skin damage.

A French ANSM lab model showed that on intact skin, aluminium penetration from an antiperspirant was extremely low. But when the same skin was “stripped” to mimic barrier damage, aluminium penetration increased sixfold. This is a lab simulation, which doesn’t tell us how much gets into the bloodstream in real life, but it does show that barrier integrity matters.

Aluminium and Breast Cancer: What the Research Shows

2003 study: Researchers studied 437 breast cancer survivors and found something concerning. Women who shaved frequently and used antiperspirants, particularly those who began both habits at a young age, were diagnosed with breast cancer at an earlier age than those who shaved less often or applied products less frequently. This isn’t proof of causation. But biologically, it fits the idea that damaged skin might allow more aluminium to enter, and that earlier onset, longer exposure could matter more for some women than others, maybe those with a genetic predisposition, for example, it may make a difference in their risk for cancer.

• Mirick et al.: Compared breast cancer patients with controls and found no difference in antiperspirant or deodorant use.
• 2024 meta-analysis: Pooled data from seven case-control studies - a pretty good quality one and still found no statistically significant association (OR 0.96, 95% CI 0.78–1.17) between antiperspirant use and cancer risk.
• Breast cancer patients in radiotherapy: Aluminium deodorants did not increase skin toxicity; banning them often caused distress about body odour.
• 2023 bromhidrosis (a condition marked by strong underarm odour) study: The researchers used a specially formulated staining antiperspirant before surgery to track where aluminium particles ended up. Under the microscope, they found no deposits in apocrine sweat glands. The aluminium stayed confined to the superficial eccrine ducts, where it exerts its sweat blocking effect.

These studies plus the 2024 meta-analysis are on one end, and on the other end, some studies, like the shaving plus antiperspirant, plus the report of the lady with high blood aluminium levels, show some risk. Some researchers, like Darbre and others, have reported higher aluminium concentrations in tumour tissue, especially in the upper outer quadrant of the breast - the same area closest to the underarm, where these products are applied.

So at this point, we cannot say that aluminium in deodorant causes cancer, we also can't say that you can use these forever. Because aluminium is a metalloestrogen and can interact with hormone receptors in the body.

Putting Aluminium in Perspective

• From antiperspirants: 50,000–75,000 μg/day applied, but only a trace absorbed.
• From diet: 4,000–9,000 μg/day (tea leaves, cereals, shellfish).
• From antacids: Millions of μg/day.

So, even if aluminium penetrates skin under certain conditions, antiperspirants add only a fraction of overall aluminium exposure.

Then, why are aluminium antiperspirants often singled out? Largely because the application site is close to breast tissue, the use is frequent and long-term, and unlike diet or pollution, it’s an exposure we can choose to modify more easily.

The Regulatory View

• EU SCCS (2020): Concludes that non-spray antiperspirants are safe on healthy skin at concentrations of up to 10.6% elemental aluminium.
• US FDA: Permits up to 25% aluminium chlorohydrate, reflecting long-standing OTC antiperspirant monograph limits. So the 25% limit is drawn from research that has gone into these monographs.
• French AFSSAPS: Takes the most cautious position, recommending no more than 0.6% aluminium chloride and avoiding use on broken or irritated skin.

Here’s the problem: 0.6% aluminium is well below the threshold needed to form the gel like plugs in sweat ducts that give antiperspirants their effect. At that level, you have essentially stripped away the “anti-sweat” function, leaving only odour masking. In other words, it may be safer by precautionary standards, but it’s no longer an antiperspirant in the true sense.

Practical Takeaways

1. Avoid applying aluminium based antiperspirants immediately shaving, waxing, or exfoliation.
   • Damaged skin = more absorption. Micro-cuts and stripped skin can increase aluminium absorption by up to six times.
   • If you need odour control right after shaving, consider a non-antiperspirant deodorant for that day, then resume antiperspirant use once the skin has recovered. Or shave the previous night, and you can use the antiperspirant the next morning.
   • Reduce the frequency of shaving; if you catch yourself shaving often, then you may enjoy laser hair removal. Again, no aluminium antiperspirant for a few days after laser hair removal.
2. Low-aluminium ≠ functional antiperspirant.
   • At the 0.6% aluminium level, which is what you may see from some imported products or those calling themselves natural and non toxic, sweat duct plug formation is negligible, meaning you get almost no sweat reduction effect. This is fine if odour masking is your only goal, but it’s not a functional antiperspirant.
3. Stick to healthy, intact skin.
   • Intact skin has a low absorption rate (0.012% in the Flarend human study). Compromised skin, through irritation, dermatitis, or barrier damage, can allow much higher uptake.
   • If you have recurrent underarm irritation, alternate with aluminium-free days or switch to a gentler formulation, or speak to your dermatologist.
4. Residue management
   • If you are concerned about long-term surface build-up, occasional mild exfoliation (e.g., with lactic acid rather than salicylic acid for better tolerance in the underarm) can help clear residues without irritating the skin.
   • Again, leave a gap between exfoliation and applying antiperspirant.
5. Weigh personal risk factors
   • For most people, current evidence does not support a ban on aluminium-based antiperspirants when used as directed.
   • Those with a high genetic predisposition to breast cancer (e.g., BRCA mutations) or compromised skin barriers may choose a lower-aluminium or aluminium-free option as part of a broader precautionary approach - we call this the precautionary principle.
   • Sometimes, you may not be able to do this on your own, so consult your dermatologist.

To conclude, Aluminium containing antiperspirants remain an effective and generally safe choice for sweat control within existing regulatory limits. The clearest evidence-based advice is: do not apply them on broken or freshly shaved skin. Beyond that, the choice comes down to personal comfort with risk rather than a directive from current science.

1. Aluminium and the human breast. Darbre PD.Morphologie. 2016.
2. Aluminium and breast cancer: Sources of exposure, tissue measurements and mechanisms of toxicological actions on breast biology. Darbre et al., J Inorg Biochem. 2013.
3. Effect of aluminium on migration of oestrogen unresponsive MDA-MB-231 human breast cancer cells in culture. Bakir et al., J Inorg Biochem. 2015
4. Aluminium, antiperspirants and breast cancer. Darbre PD., J Inorg Biochem. 2005.
5. Aluminium and human breast diseases. Darbre et al., J Inorg Biochem. 2011.
6. Metalloestrogens: an emerging class of inorganic xenoestrogens with potential to add to the oestrogenic burden of the human breast.Darbre et al., J Appl Toxicol. 2006.
7. Aluminium in cosmetics and personal care products. Sanajou et al., J Appl Toxicol. 2021.
8. Are Antiperspirants Safe? Shedding Light on the Distribution of Aluminum Compounds in Sweat Glands. Ho WT., Plast Aesthet Nurs (Phila). 2023
9. Avoiding antiperspirants during breast radiation therapy: Myth or sound advice? Baumann et al., Radiother Oncol. 2017.
10. Antiperspirant use and the risk of breast cancer. Mirick et al., J Natl Cancer Inst. 2002.
11. Breast Cancer and Deodorants/Antiperspirants: a Systematic Review. Allam MF. Cent Eur J Public Health. 2016.
12. Aluminum Content of Human Milk and Antiperspirant Use. Rochman et al., Breastfeed Med. 2021.
13. Systematic review of potential health risks posed by pharmaceutical, occupational and consumer exposures to metallic and nanoscale aluminum, aluminum oxides, aluminum hydroxide and its soluble salts. Willhite et al., Crit Rev Toxicol. 2014.
14. SCCS (Scientific Committee on Consumer Safety). Opinion on the safety of aluminium in cosmetic products – Submission II. SCCS/1613/19. Final Opinion, 3–4 March 2020
15. Deodorants and antiperspirants: New trends in their active agents and testing methods. Teerasumran et al., Int J Cosmet Sci. 2023 Aug;45(4):426-443.
16. The Potential Metalloestrogenic Effect of Aluminum on Breast Cancer Risk for Antiperspirant Users. Sawicka et al., 2024.
17. If exposure to aluminium in antiperspirants presents health risks, its content should be reduced. Pineau et al., J Trace Elem Med Biol. 2014.
18. The Health Effects of Aluminum Exposure. Klotz et al., 2017.
19. Exploring the Potential Link between Aluminum-Containing Deodorants/Antiperspirants and Breast Cancer: A Comprehensive Review. Hangan et al., 2025.
20. Correlation between daily life aluminium exposure and breast cancer risk: A systematic review. Moussaron et al., 2023.
21. Use of Antiperspirant Products and Risk of Breast Cancer: A Meta-Analysis of Case-Control Studies. Trinh et al., Cancer Invest. 2024.
22. National Cancer Institute. Antiperspirants/deodorants and breast cancer [Internet]. Bethesda (MD): National Cancer Institute; 2023 [cited 2025 Sep 10].