In honour of the annual hoards if bleary-eyed hayfever sufferers, we are joined by Carrock Sewell who describes how the immune system works, what causes allergic reactions and how we might be able to cure them, and Mark Booth discusses parasites, how they suppress and evade the immune system and how the Matangini Project attempts to provide parasite-free water in Africa. Sticking with the African continent, Derek Thorne travels to Tanzania to learn how to make ugali in Kitchen Science.