Part of the show Fireworks, Explosions and Chemistry
Linda in Norwich asked:
Why do we feel better after sneezing?
A sneeze is a bit like an itch in your nose. When you have an itch, it's extremely pleasurable to scratch it. Unless you have really long fingers, it's not that easy to scratch that far up your nose! So what sneezes do is use air to perform a metaphorical scratch. What we know about itching is that there is a special class of very small nerve fibres, and they signal itchiness. In fact, you can switch off the signals into the spinal cord and brain for itchiness if you cause a little bit of pain. That's why scratching an itch actually helps to relieve an itch, because you cause a little bit of pain and it switches off the itch signal. In sneezing, you get that pleasant relief because you've got rid of the itchy sensation, and also dislodged some of the gunge that's in your sinuses.