This is the ingredient that makes an antiperspirant an antiperspirant. Everything else in the stick is texture, scent and marketing. It is also the ingredient people have been told most often to fear, usually by a brand selling something without it.
| Field | Aluminium salts |
|---|---|
| What it is | A family of aluminium based salts, most commonly aluminium chlorohydrate in everyday products and aluminium chloride hexahydrate in stronger clinical strength ones. On a label they appear by name, near the top of the list. |
| What it does | Reduces the volume of sweat reaching the skin surface by forming a temporary plug in the upper sweat duct. It does not address odour directly, and it does nothing for apocrine secretion beyond reducing the moisture bacteria feed on. |
| Evidence strength | Strong for the effect. Sweat reduction from topical aluminium salts is long established, dose dependent and the basis of clinical treatment for excessive sweating. Weak to absent for the claims made against it, which are covered below. |
| Who avoids it | Anyone with broken, freshly shaved or actively irritated underarm skin, until it settles. Anyone who has reacted to it repeatedly. If you have kidney disease, aluminium exposure is a question for your clinician rather than a website. |
| What it clashes with | Shaving immediately before application, damp skin, and stacking a clinical strength product on top of a daily one. Nothing in a skincare routine interacts with it chemically, because it is not doing anything to the rest of your face. |
What happens in the duct
Sweat comes from eccrine glands, which are distributed across most of the body and produce a watery, largely odourless fluid for cooling. When an aluminium salt dissolves in that sweat, the aluminium forms an insoluble gel with proteins and other material already in the duct. That gel sits as a plug in the upper part of the duct and physically limits flow.
The plug is temporary. It is shed as the surface layers of skin turn over, which is why an antiperspirant needs reapplying every day or two rather than once a season, and why the effect builds over the first few days of consistent use rather than arriving fully formed on day one.
Two consequences follow, and both are practical. Because the salt has to dissolve in sweat to work, applying it to skin already running with sweat mostly washes it away. And because sweat production is at its lowest overnight, the plug forms most effectively when you apply before bed rather than after a morning shower.
Apply to dry skin, at night, and do not wash it off in a panic in the morning. That single change does more than switching brands.
Strength, and where the ceiling is
Everyday antiperspirants use aluminium chlorohydrate at cosmetic concentrations. Products aimed at heavier sweating typically use aluminium chloride hexahydrate, which is more effective and more irritating, and which is the same active used in the first line treatment for excessive underarm sweating. The trade off is straightforward: more sweat reduction, more chance of stinging and itching, particularly on shaved skin.
The exact salts permitted, and at what concentration, vary between markets and between product formats, so the ingredients list on the pack in your hand is the only reliable statement of what you are applying. Aerosols, roll ons and sticks are not interchangeable in this respect.
If a clinical strength product used correctly for a few weeks is still not enough, the next steps are medical rather than cosmetic, and excessive sweating has recognised treatment pathways. That is a conversation with a GP, and the NHS page on hyperhidrosis sets out what those pathways are.
Deodorant and antiperspirant are not the same product
A deodorant targets odour. Fresh eccrine sweat is close to odourless; the smell comes from skin bacteria breaking down the richer secretion produced by apocrine glands, which are concentrated in the underarm. Deodorants work by reducing that bacterial population, by altering skin surface conditions, or by masking with fragrance.
An antiperspirant reduces the sweat itself. Most commercial products do both jobs, which is why the distinction gets lost. It matters when a product is failing. If you are dry but still smell, the problem is bacterial and an antiperspirant will not fix it. If you are soaking through shirts, no amount of fragrance is the answer. The mechanism behind that split is covered in our feature on sweat, odour and what actually controls it.
The claims made against aluminium salts
Two claims circulate widely, and both are worth stating precisely rather than dismissing.
The first is that antiperspirants cause breast cancer, usually via a story about blocked toxins or absorbed aluminium. Cancer Research UK addresses this among the cancer claims it examines, and the position is that there is no good evidence linking antiperspirant or deodorant use to breast cancer risk. The underlying premise is also wrong: sweat is not a route by which the body clears carcinogens.
The second is a link with neurological disease. Aluminium exposure from cosmetics has been formally reassessed by the European scientific committee that evaluates cosmetic ingredient safety, which considered dermal absorption data and concluded that use in these product types is safe within the concentrations it set out. The absorbed fraction through intact skin is very small relative to dietary intake, which is where most human aluminium exposure comes from.
None of that makes an aluminium salt compulsory. If you do not sweat much, a deodorant without one is a perfectly reasonable product and there is no penalty for choosing it. What we would not do is choose it out of a fear that the evidence does not support.
Getting more out of the one you already own
- Apply at night, to fully dry skin. The single highest impact change.
- Do not shave immediately before applying. Leave it to the following day if the skin feels raw.
- Give it three or four consecutive nights before judging whether it works.
- Do not scrub it off in the morning shower. A rinse is fine; a vigorous exfoliation removes the plug you spent the night forming.
- If it stings, drop the strength rather than the habit.
What this card does not cover
This is a card about one ingredient. It is not a routine, not a product recommendation and not clinical advice. We name no brands here and never will. Excessive sweating that affects your life is a medical matter with real treatments behind it, and the right move is a GP appointment rather than a fourth stick from a supermarket shelf.
Sources
- NHS, excessive sweating and its treatment pathways, including the role of stronger aluminium chloride preparations. Accessed 15 August 2026.
- Cancer Research UK, on claims that link everyday products including antiperspirants to cancer risk. Accessed 15 August 2026.
- Scientific Committee on Consumer Safety, the body that published the safety reassessment of aluminium compounds in cosmetic products. Accessed 15 August 2026.
- British Association of Dermatologists, patient information on hyperhidrosis and underarm skin irritation. Accessed 15 August 2026.
Reviewed 15 August 2026. The safety assessments are the part of this card most likely to be revised, and they are the part we recheck.