Alum As Antiperspirant


A question about alum from Alice.

Hello Colin,

Thank you for taking the time to write such a informative blog. I have a question concering potassium alum. I have been researching this product and I keep seeing comments like “its a compound” so it does not contain aluminium. KAl(SO4)2  does contain potassium and aluminium so can you please explain to me (us) if there is Al in here for those of us who try to steer clear of this stuff in our deo/antiperspirants. Thank you very much. Kind regards, Alice

Hello Alice,

Thanks for the kind words and sorry it has taken a while to reply. 

I have taken the liberty of slightly modifying what appeared in my e-mail inbox to what I think you are referring to.  The compound that gets used in some natural antiperspirants is usually referred to as alum, though calling it potassium alum is more precise because there is a whole family of alums.  For example there is sodium alum where the role of the potassium is taken by sodium.  But they all contain aluminium which is the element that you are interested in.

Aluminium when dissolved in water is trivalent, which means it has three positive charges on it.  These act as hooks which can react with other compounds.  This can be a useful property.  For example aluminium salts are often used in water purification processes.  Large molecules react with the positive groups.  As there are three available, often three large molecules will end up joined to one aluminium one.  This new very large molecule is heavy and drops to the bottom of the tank, conveniently taking the aluminium with it.

The people who treat water know what they are doing and carefully match the amount of aluminium to the impurities they are working on.  But there was an incident in the UK in the eighties at a place called Camelford where far too much aluminium was used by mistake and which ended up contaminating some drinking water.  The people who drank the water were often physically sick and have suffered a range of symptoms ever since including skin colour changes and blisters, through to memory problems and dementia.

There have been long standing concerns that aluminium might play a role in Alzheimer’s disease and the mental problems of the Camelford victims do seem to add credence to this.

This was a big news story at the time and I can remember being quite shocked by it.   It did make one wonder about the suitability of aluminium for a number of applications.  I have to confess that it has probably prejudiced me against aluminium, so please bear my bias in mind.   Since then I have avoided aluminium cookware and I only use aluminium foil for cooking when it is unavoidable (i.e., when ‘cooking’  a turkey at Christmas – when I do it is more like an energy intensive dehydration process so nobody eats very much of it).

I don’t think anyone has ever worked out for sure how aluminium works as an antiperspirant, but I think it is probably down to its trivalent nature creating insoluble aluminium salts in the pores that reduce the rate of sweating simply by physically blocking it.

So is aluminium in antiperspirants a health risk?   It certainly sounds like there might be an issue there.  But aluminium is a naturally occurring element which we can cope with just fine at normal levels in our diet, so the small amounts we apply to our armpits are unlikely to contribute even a measurable amount to our blood levels.  And if it is working by forming insoluble compounds the chances are a lot of it is getting trapped in the pores and getting no further than the armpit.

In addition to this, according the Alzheimer Society the weight of evidence linking aluminium to brain damage is tipping away from aluminium being a problem.  I haven’t reviewed the data myself, but I imagine they know what they are talking about.  This is an issue that has bothered me for a long time but I think my mind is now at rest.

Which finally brings us to alum.   I think that the aluminium in the alum when applied to the skin will behave in a manner similar to the aluminium in conventional antiperspirants.  I don’t have any actual data, but I have tried alum myself.  I found that it worked a bit, but not as well as standard ones.  Purely on that basis my guess is that the rate of aluminium release is slower.  If aluminium dose pose a health risk as antiperspirant – I no longer think it does but I am not infallible – then alum is probably a lower risk but is not a zero risk. You’ll have to make your own mind up.

Thanks to Wikipedia for the moody shot of an alum crystal


3 thoughts on “Alum As Antiperspirant”

  1. I would be interested to know (if it is not too personal) if you use deodorant with any of the aluminium’s in ? I have been using potassium alum crystal for many years now and happily until articles mentioned above appeared. However, finding an alternative that isn’t stuffed full of flower extracts (to which I am allergic) isn’t easy. It is also a very costly trial and error event.

    1. I use a standard supermarket own brand which I guess contains about 4% aluminium. I would carry on doing what you are doing. You are getting a lower aluminium exposure than people like me, and the only lower aluminium alternative is to forego using a deodorant altogether.

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