Potassium Alum – Aluminium or Not?

Danielle, who is a chemist, left a great comment on an earlier post not too long ago. Her comment inspired me to revisit the ingredient you see above (in crystal form) and try to answer a few questions.

This ingredient is used – among many other things – as an active in deodorants. It's called potassium alum.

So, what the heck is Potassium Alum?

Potassium alum is a naturally occurring chemical compound. This compound occurs when certain minerals (sulphide and potassium-bearing ones) come into contact with oxygen molecules. When this happens, potassium alum appears as encrustations on the minerals.

These encrustations of potassium alum can be found all over the planet, but predominately in Europe, North and South America (see this post for a map of potassium alum hotspots).

Potassium alum can also be described as an aluminium salt.

Aluminum - The Element and The Salts

There is aluminium - the element. There are also aluminium salts. They are 'related', but there are differences.  I've linked to nerdy stuff here and there (as well as below), but will give you a few headines here.

Although aluminium is the 3rd most abundant element on the planet, aluminium – the metal – is not nearly as common in nature as aluminum salts are.

Aluminium metal is very reactive (read: depending on what it comes into contact with, it will change form, or react in one way or another. See this page for more info).

The metal is commonly found in packaging, wires, food containers, etc.

Aluminium salts are the result of a process (for example, how potassium alum occurs in the description above).

The salts are commonly found in medicines, foods, and cosmetics (such as deodorants).

Where This Particular Salt Shines

Potassium alum has many uses: for example for water-purification, in dyes, and for tanning. It is also likely sitting in your kitchen cupboard right now if you have happen to have baking powder in the house.

Potassium alum has a history of use as an astringent, and its anti-sceptic properties make it ideal for helping stop bleeding in minor cuts.

If you happen to know someone who shaves 'the old fashioned way', you may also find they have a small bar of 'shaving alum', which is 100% potassium alum. It is used to stop bleeding from minor cuts.

I've tried using potassium alum to stop a minor cut from bleeding and it was super effective and didn't even sting. No wonder razor-shaving gents swear by their shaving alum.

So, Does Potassium Alum Contain Aluminium?

Danielle answered this quite well in (part of) her comment:
"All commercial deodorants containing aluminum contain it in a salt form (not the metal form). The salt form may effect the bio-availability of aluminum ion, but all aluminum salts contain the element aluminum."

 Aluminum?! Should We be Worried? Is it Safe?

To answer, I will refer you to what science has been able to establish about aluminium and deodorant. To date, science has not been able to link any sickness or disease to aluminium in antiperspirants.

Science is still studying the effects of exposure to aluminium. What can be considered as a 'safe amount' of aluminium exposure has still not been established.

A small percentage of people are allergic to aluminium. People who are allergic to aluminium will obviously have a reaction to being exposed to it.

A few informational tidbits:

Wikipedias article on aluminum - under the section, Health Concerns:
'Aluminum salts are remarkably nontoxic' (link)
"Although there is little evidence that normal exposure to aluminium presents a risk to healthy adults, some studies point to risks associated with increased exposure to the metal." (link)

In 2001 Aluminum clorohydrate absorption from one-time use was tested.
"Results indicate that only 0.012% of the applied aluminium was absorbed through the skin. At this rate, about 4 microg of aluminium is absorbed from a single use of ACH (aluminum clorohydrate) on both underarms. This is about 2.5% of the aluminium typically absorbed by the gut from food over the same time period. Therefore, a one-time use of ACH applied to the skin is not a significant contribution to the body burden of aluminium." (link)

Antiperspirant and deodorant allergy test results
"The most commonly occurring allergen in 107 tested deodorants and antiperspirants was fragrance - perfume." (link)

USA: Agency for Toxic Substances and Disease Registry
"An average American adult eats about 7-9 mg of aluminium every day through their food." (link)

LisaLise on Potassium Alum

My daily deodorant for years has been either potassium alum in the form of a crystal deodorant, or a deodorant of my making that contains some potassium alum. My extremely sensitive skin doesn't react to it at all and I find it both effective yet gentle.

I do, however, continue to follow scientific study on aluminium exposure with great interest. So far, no scientific evidence has given me any cause to search for alternatives to what I am using.

In short, I am quite comfortable using potassium alum on a daily basis.

Potassium Alum Fun

Did you know you can actually grow your own potassium alum crystals? Check this page for a how-to.

Links to More as well as some Nerdy Stuff

Aluminum, antiperspirants and breast cancer (pubMed - 2005)
Dermal absorption of aluminum from antiperspirants (pubMed- 2001)
Metalloestrogens (PubMed - 2006) 
SCCS (Scientific Commitee on Consumer Safety) on Aluminium in Cosmetics (2014)
Earlier post on this blog about aluminum and anti-perspirants
Human Health Risk Assessment for aluminium (J Toxicologic Envir. Health)
Aluminum - the metal (wikipedia)
Aluminum sulphate (wikipedia)
Potassium alum (wikipedia)
Antiperspirant and deodorant allergy (pubmed case)
The post with Danielles comment (scroll to the near bottom to find Danielles comment)
Is aluminium really a silent killer? (2012 article from the Daily Telegraph)
US: Public Health Statement about aluminium (2008 - Agency for toxic substances and Disease registry)

Photo of potassium alum crystal at top of page - courtesy of Wikipedia


María Zamora said…
I'm not sure if my comment was published, it seems not.
Just to say how much I loved and enjoyed this post of yours, so full of objective information without the typical scaremongering background.
Thank you so so much :)
Lise M Andersen said…
Thank you Maria! :D
Steve said…
Thanks. Brilliantly written. I actually understood you. Now I know what to do and why I was struggling.
Lise M Andersen said…
Thank you for your kind comment Steve.