Why does chilli make my head itch?

Why don't birds get electrocuted on an electric fence? Why do I want to sing along to tunes I know? Does a cut onion soak up toxins from the air? Is Everest really the tallest mountain? Why does chilli make my head itch after I've shaved off my hair? What's the prospect of terraforming Mars? And can women synchronise their periods? Plus, news of the New Horizon's probes fly-by of Kuiper Belt Object (KBO) Ultima Thule, with Chris Smith and Eusebius McKaiser... Like this podcast? Please help us by supporting the Naked Scientists