How do painkillers ‘know’ where to take away pain?

Most pain is caused by damage to the body’s cells, communicated by specialised nerve cells called nociceptors, which run between the spinal cord and skin, muscles, some internal organs and our teeth. When something is distressing your body enough that it may
damage your cells, nociceptors send an electrical message to your brain that you experience as pain.

Typically, nociceptors only fire when sensations reach a high threshold. When cells in your body are damaged, they can lower this threshold by releasing tuning chemicals. Ibuprofen or aspirin stop the production of one class of tuning chemicals, called prostaglandins.

This keeps the nociceptor firing threshold higher to minimise the pain we experience. The blocking chemical enters your bloodstream, which carries it throughout your body. So, painkillers don’t ‘know’ – they go everywhere, reaching the damaged cells in the process.