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Antiperspirants
An antiperspirant reduces sweat; a deodorant only kills the bacteria that make sweat smell. That one mechanical difference is the whole debate. The internet has insisted for decades that the aluminium causes breast cancer or Alzheimer's, and both claims have been tested directly and come back null. The downside that is real, and that almost nobody warns you about, is a red itchy patch, and it's fixed entirely by how and when you put the stuff on.
Do ยท Daily Evidence Moderate Chapter Skin

The plug is built from your own sweat. The aluminium salt dissolves in the first bit of sweat it meets, grabs onto sweat proteins along the duct wall, and knits them into a thin film that thickens until the duct closes 1. It grows from the walls inward rather than capping the pore, and it sheds with normal skin turnover in 7 to 14 days, which is why you reapply daily. A deodorant does none of this; it kills the armpit bacteria that eat sweat and produce the smell, and leaves the sweat where it is.

A drugstore stick cuts armpit sweat by a quarter to a third. For most people that stops visible marks on a shirt, and it's not a contested effect. The group the articles forget: about one in twenty people sweats enough to meet the medical definition of hyperhidrosis, scoring the daily impact as severe as moderate psoriasis 2. For them the shelf stick is undertreatment, and the answer is a dermatologist and a prescription-strength lotion rather than another brand.

Timing does most of the work. Three rules, all cheap.

Deodorant is a complete answer if you don't care about wetness. It handles the smell and does nothing about the damp; switch and you'll notice within a day the smell is fine and within two the shirt is wet. There's no third product that gives dryness without aluminium. And the "natural" crystal or alum sticks are not aluminium-free โ€” alum is an aluminium salt, and it reduces sweat the same way, just slower. If avoiding aluminium is the point, a crystal stick is the wrong choice.

The fine print โ€” when to skip it, and what people get wrong

Breast cancer: null across the studies and a 2023 review 3 4. Alzheimer's: null 5. About 0.002% of what you apply reaches your blood, far below the milligrams you eat daily 6 7.

Never apply to broken skin, active eczema, or freshly shaved skin. If you flare, switch to a gentler formulation and add 1% hydrocortisone for a few days. True aluminium allergy is under 1% and recurs regardless of formulation.

References
  1. 1Bretagne et al. (2017). The mechanism of eccrine sweat pore plugging by aluminium salts using microfluidics combined with small angle X-ray scattering. Soft Matter. link
  2. 2Strutton DR, Kowalski JW, Glaser DA, Stang PE (2004). US prevalence of hyperhidrosis and impact on individuals with axillary hyperhidrosis: results from a national survey. Journal of the American Academy of Dermatology. link
  3. 3Moussaron et al. (2023). Correlation between daily life aluminium exposure and breast cancer risk: A systematic review. Journal of Trace Elements in Medicine and Biology. link
  4. 4National Cancer Institute (2022). Antiperspirants/Deodorants and Breast Cancer. link
  5. 5Graves AB, White E, Koepsell TD, Reifler BV, van Belle G, Larson EB (1990). The association between aluminum-containing products and Alzheimer's disease. Journal of Clinical Epidemiology. link
  6. 6de Ligt et al. (2018). Assessment of Dermal Absorption of Aluminum from a Representative Antiperspirant Formulation Using a 26Al Microtracer Approach. Clinical and Translational Science. link
  7. 7SCCS (2020). SCCS Opinion on the safety of aluminium in cosmetic products (SCCS/1613/19). link
Related in the handbook (2)
Related
  • โ€” Scented antiperspirants are a common fragrance source against thin underarm skin.
  • โ€” If you want to dodge these ingredients, antiperspirants are one product to check the label on.
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