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Metal salts, especially aluminum compounds are used in antiperspirants to prevent sweating. I found out aluminum chloride hexahydrate, which is found in most antiperspirants, undergoes an acid-base reaction with water which causes the proteins to denaturate, thus these proteins are precipitated out as a gel blocking the sweat glands. Additionally, aluminum is able to bind water molecules.

However, I would like to understand the biological and chemical processes in more detail as I am not quite sure why there is no effective alternative to metal salts to prevent sweating. There are many compounds that could undergo an acid-base reaction with water. There are also different metal salts which are able to bind several layers of water.

My specific questions are:

  • Which biological and chemical processes underlie the effect of antiperspirants that make metal salts so effective?
  • Why are aluminum salts used most commonly?
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    $\begingroup$ Zirconium is also used. See en.wikipedia.org/wiki/Aluminium_zirconium_tetrachlorohydrex_gly $\endgroup$ – DrMoishe Pippik May 23 '19 at 2:25
  • $\begingroup$ Is there any reason to believe that aluminum is the 'most effective' at preventing sweating, as opposed to 'effective enough' given cost, toxicity, manufacturability, and a dozen other dimensions? $\endgroup$ – Jon Custer May 23 '19 at 12:40
  • $\begingroup$ Aluminum ions are also used for medical purposes (hyperhidrosis). If there was a better option, wouldn't it be used for those applications? $\endgroup$ – jona173 May 23 '19 at 15:33
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    $\begingroup$ Great question! I've often thought this myself! $\endgroup$ – Melanie May 25 '19 at 7:27
  • $\begingroup$ @Melanie I thought of answering some old unanswered questions, so here is one ;) $\endgroup$ – Nilay Ghosh Jun 25 '20 at 5:56
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  • Which biological and chemical processes underlie the effect of antiperspirants that make metal salts so effective?

Aluminium-based complexes present in the antiperspirants react with the electrolytes in the sweat to form a gel plug in the duct of the sweat gland. The plugs prevent the gland from excreting liquid and are removed over time by the natural sloughing of the skin. From a biological point of view, it interact with the keratin fibrils in the sweat ducts and form a physical plug that prevents sweat from reaching the skin’s surface.

  • Why are aluminium salts used most commonly?

Aluminium salts have a astringent effect on the pores causing them to contract, further preventing sweat from reaching the surface of the skin. Aluminium salts are also natural antimicrobial agents, so they control bacteria on the skin, reducing unpleasant odors.

Some of the aluminium salts used in antiperspirants:

  1. Aluminium chloride
  2. Aluminium chlorohydrate
  3. Aluminium zirconium tetrachlorohydrex gly (an aluminium-zirconium compound)
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