Science Questions

How do odour-abating insoles work?

Sun, 14th Mar 2010

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Craig Campbell asked:

Hi Chris


I always try and listen to your show on 567 and 702 Cape Talk its most interesting.


What is your take on this product?


I have been wearing a shoe insole that has a activated carbon content , this is to kill the odour of smelly feet and shoes.


I have been using this product for about 3 month and find that my feet and even the shoes do not smell,do you have any knowledge on this type of product ?


Can activated carbon harm the skin if it makes contact? I find the product works great just wondering what the science behind the removal of the odour is?


Once a month†I rinse the insoles under the tap to wash them clean as recommended by the makers


Look forward to your comments,


Kind regards



Chris -   Most of them have got activated charcoal in them.  All that means is that itís charcoal with a big surface area, and this means you've got carbon, which can soak up noxious odours.

So you have something that can lock away odours, thatís the first point, and it will also do another thing, which is soak up water.

Your feet squirt into your socks something like a quarter to half a litre of sweat every day.  At the same time, you've got skin cells falling off at the rate of thousands every second from all parts of your body, but your feet especially because the skin on your feet is a bit thicker. 

So what you've got are all of the elements of the perfect microbiological or bacterial banquet going on on your feet:  youíve got food in the form of dead cells, you've got water in the form of sweat, and you have warmth.

All these things add together to very active, hungry bacteria being well fed. Consequently, they produce various chemicals, some of which are whiffy Ė smelly; they're volatiles.

But if you put these odour eating things into your shoes, they soak up the water for a start, which means that thereís less to keep the bacteria lubricated so they don't grow as well, and they also soak up some of the noxious gases because they have a big surface area and they can adsorb those materials, which prevents them from being so pungent. 

So they work in a number of ways, but thatís chiefly how it does it.


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