Like all consumer products, sofas come with instructions for how best to use and maintain them.

But it may surprise you that many furniture companies warn medicines can seep out of your sweat or body oils to damage your leather sofa.

People who repair leather sofas warn about this too. They say this can lead to the leather fading, cracking or discolouring.

So which medicines are they talking about? And how worried should you be about them damaging your furniture?

Different drugs, different body parts

When you take a drug – as a tablet, injection or other form – it is distributed to different parts of the body. And someone would likely have a detectable amount in most bodily fluids. This includes breast milk, tears, seminal fluid, saliva and sweat.

How much of the drug reaches each part of the body, and where it ultimately accumulates, depends largely on the drug’s specific properties.

Water-soluble drugs, such as aspirin and paracetamol, tend to accumulate in blood serum and other bodily fluids. Oil-soluble drugs, such as testosterone and ketamine, tend to accumulate in the organs and fat stores.

When it comes to excretion, most of the drug will be filtered by the kidneys and removed from the body in urine. The amount of drug usually excreted in faeces is low and is mostly due to small quantities of drugs you take by mouth that didn’t end up getting........

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