Scientists have — for the first time — shown how chemical triggers in the nervous system can amplify the pain experienced by mammals in response to certain stimuli.

The pain system probably evolved to alert them to life-threatening dangers. As they approach objects that are extremely hot or cold or are biting them, they experience intense pain — allowing them to get out of harm’s way.

But in certain diseases, that defence mechanism malfunctions and rather than providing a short, sharp shock — it produces long-term, chronic pain, seen with some conditions affecting humans such as neuropathies, arthritic pains or migraines.