How can you remove body odour from clothes?

07 May 2019

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Shirts drying on a washing line

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Question

How can you remove body odour from materials?

Answer

Izzie Clarke received this chemical query from Europan Ocean on The Naked Scientists Forum, which also inspired fellow panellist Bill Colledge to chip in. It was over to chemist and writer, Kit Chapman, to sniff out an answer for them...

Kit - Well, you could set the material on fire, that will certainly get rid of everything. But assuming you want to keep your clothes, let's have a look at what body odour is. Your body will naturally release all kinds of secretions, sweat is a great example, and the natural bacteria that live on your skin, and everyone has it it's perfectly normal, they will start breaking those down and release molecules that stink. And they'll react with your nose sensors and that's how your find out that you're a bit wiffy.

So when things dry on your clothes, what can you do? One thing is to wash them. Water is fantastic for getting rid of those horrible smells and also you can use a detergent. Now, detergents are fantastically shaped molecules because they have what we call a hydrophobic tail.

Izzie - Now, that means that they are essentially afraid of water?

Kit - Exactly. The tail is afraid of water, but the head loves water. So it sticks the tail in those fats, it breaks things up and gets rid of them, and that's how we get rid of dirt, and that's why you use washing-up liquid to clean your plates, same kind of principle. So you can get rid of stenches that way.

The other thing you can do is try and neutralise them. One thing that works very well is actually using white vinegar in a bowl of water and that will absorb the smells from the room and neutralise them.

Izzie  - And so why is it that combining that with water, that white vinegar, gets rid of it?

Kit - It's not necessarily combining it with the water, it's just making sure that the white vinegar is actually going around the room essentially. It's because of an acid-base reaction. It's very very basic chemistry.

Speaking of basic chemistry another thing, and other brands are available, but Febreze is a great example of how you can actually trap these smells. Febreze has a structure in it called a cyclodextrin and that's shaped like a donut. It has a big hole in the middle, it's a sort of a circular molecule. And what it'll do is it will get those molecules in there that are causing the horrible smells inside that circle and trap them. You can't smell it and the molecules are still there, but the BO's gone.

Izzie - Oh Bill, you've got a question.

Bill - Yeah. I know some people use sodium bicarbonate to put in the microwave to eliminate smells. How does that work?

Kit - We're going exactly the same kind of route as the vinegar. Sodium bicarbonate is a great version of a base and it will cause that same kind of reaction. So it depends really what the smells are as to how you get rid of them. But sodium bicarbonate - fantastic for cleaning products and these things are really really cheap. Everyone thinks that you need to go for really expensive cleaning product, but actually white vinegar, sodium bicarbonate, things that we've used for over a hundred years now are just terrific.

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