Alum stone, miracle deodorant or disguised aluminum?

Written on 05.Nov.19 by Anne-Marie - Updated 14.Jan.21

Alum stone is often cited as a healthy alternative to conventional deodorants filled with aluminum salts. Result of an effective communication plan or reality? What if everything doesn't smell so good with Alum stones? Before entrusting them with our armpits, let's take a closer look.

The alum stone, the perfect deodorant?

The alum stone has a really reassuring name, don't you think? It sounds REALLY natural, doesn't seem to refer to any controversial substance. It is understandable that it has been the refuge of our armpits when the harmful effects of conventional deodorants have been in the media.

Indeed, the alum stone is of mineral origin. And it has great assets for our fight against halos and unwanted odors. In terms of effectiveness, it is at the top: antiseptic against the bacteria responsible for bad smells, slightly astringent to gently regulate without blocking excessive perspiration, it remains effective for several hours. Even at high temperatures. It rarely irritates and does not cause allergies. Odourless, it leaves no trace on clothes and is very easy to use: simply apply it damp under clean, dry armpits.

Practical, it is easy to take it with you everywhere and passes air traffic control. And it's hard to find a more sustainable development : a single stone, which doesn't really need packaging, lasts for years. The icing on the cake is that it looks good in the bathroom, with its fake crystal look. It's close to perfection!

A not so natural stone...

You are already putting on your walking shoes to pick up your future deodorant in the mountains? Not so fast! Its name is misleading: the alum stone does not exist in its raw state in nature. Not so natural, our miracle deodorant... We're even on the verge of greenwashing.

In fact, there are 2 types of alum stones on the market. 100% synthetic stones, made from A to Z from Ammonium Alum or even synthetic Ammonium Sulphate, a by-product of the nylon chemical industry. We are far from our dream of stone picked up by the side of the road. And these are the ones usually found in the components of deodorants made from Alum stone . Antiperspirants, actually. What is the Alum stone... and which is not recommended for our good health (read more: Antiperspirants and deodorants: what's the difference?).

But the alum stone presented as natural is not really natural either. To make them, rocks rich in Alum potassium are extracted from mines, particularly in China where they are often socially and ecologically disastrous, rocks rich in Alum potassium: bauxite, Alum-K, kalunite, alunite. Then several chemical treatments are used to extract, purify and then recrystallize their Alum crystals: heating for several days at very high temperatures to remove their impurities, holding them in water for several months to make them porous, then filtering the crystals, which are then cut and polished. An ecobalance much less pleasing!

To know what you are dealing with: the so-called natural stones are called Potassium Alum . They are more translucent than the synthetic stones identified by the INCI name Ammonium Alum or Aluminium Alum . The whiter the alum stone, the more synthetic it is.

Alum stones: all good to throw away?

In reality, synthetic or pseudo natural, it doesn't matter. Alum stone contains aluminium whatever its origin. This is where the term Alum comes from. Yes, the picture was too good to be true: the miracle of the alum stone is due to aluminum salts... Oops! It was rightly presented as an alternative to conventional antiperspirants and deodorants, but it's not true. What's wrong with aluminium salts? They are suspected of promoting breast cancer, hormonal disorders, degenerative diseases, anaemia... (to find out more : Deodorant with natural active ingredients, effective and safe: how to avoid aluminium salts?). Our ideal deodorant is starting to smell really bad...

Whether we use 100% synthetic stone or more natural stone, aluminium is always deposited on the surface of our skin. One nuance, however: the National Agency for the Safety of Medicines and Health Products unequivocally recommends avoiding synthetic alum stones. But more natural stones would not present the same risks: the harmfulness of their aluminum salts has in any case not been demonstrated.

The manufacturers point out that the level of aluminium actually deposited on the skin is below the recommended limits and that Potassium Alum is not absorbed by the skin due to its molecular structure and negative ionic charge... while recommending not to use them when the skin is very permeable, after shaving, hair removal or in case of lesions . Hum.

So what to do? Faced with a conventional deodorant full of aluminium salts, preservatives and synthetic fragrances, one would of course prefer to turn to a so-called " natural " alum stone. But as a precautionary principle, we advise you to make a cross on ALL alum stones.

Even more so during pregnancy or in case of kidney failure. If it turns out that aluminum actually penetrates our bodies, the ingested doses would certainly not be huge. But daily. And in an area where the epidermis is particularly thin and permeable. And in addition to many other sources of aluminium, also on a daily basis, via our diet, in particular.

In short, you might as well not add to it when you have a choice. And it's all the easier since natural, effective and safe deodorant solutions exist. Natural underarms, without odours and without aluminum salts, yes, it's possible!