Capsaicin binds to the pain receptor TRPV1, which our brains also use to detect changes in temperature - that's why we think chillies are hot.But after being over-stimulated the neurons stop responding, killing the pain. This process involves the release of endorphins, which can give us a "rush" not dissimilar from the feeling of having exercised well. This may explain why some people believe that hot food is addictive.

It is sometimes said that people in hot countries use more chilli because it makes them sweat, which cools them down. But in 1998, researchers at Cornell University pointed out that the greater use of spices in countries such as India, Thailand and China was likely to be linked to their anti-microbial function. By studying recipe books from all over the world, the researchers found that spices including chilli were more likely to be used close to the equator, and were also used more in humid valleys than on high plateaux.

That may just explain the spice's world-conquering success. Just two or three years after Columbus brought capsicum seeds back from the New World in 1493, Portuguese merchants took the plants to Asia, where they would transform the cuisine.