How drugs leach out of your sweat (and can spoil your sofa)

Many medicines can seep into sweat and body oils, potentially damaging leather furniture. Water-soluble drugs like aspirin and paracetamol tend to accumulate in blood serum and other bodily fluids, while oil-soluble drugs such as testosterone and ketamine accumulate in organs and fat stores. When these drugs excrete, they can be found in urine, feces, sweat, and skin oil.

Studies have shown that various drugs, including antibiotics, anti-inflammatories, chemotherapy medications, and even common legal and illegal substances, can be detected in sweat samples. The concentration of drugs in sweat depends on factors such as the drug's solubility, molecular size, pH, the timing of drug intake, and sweating conditions.

While the drug concentration in sweat is typically very low, nanograms per milliliter, there is a potential for staining or discoloration of leather furniture due to prolonged contact. However, the study of this issue is anecdotal, and no formal research has been published. To minimize potential damage, it is advised to avoid sitting on the sofa if especially sweaty or to cover it with a protective blanket or towel.