boil cure potion potion - Simple potion to cure boils. Taught to first-years in their first Potions class with Snape (PS8)
ingredients: dried nettles, crushed snake fangs, stewed horned slugs, porcupine quills (added after taking the cauldron off the fire)
If the porcupine quills are added before the cauldron is taken off the fire, the mixture produces clouds of acid green smoke and a loud hissing, melts the cauldron, and burns holes in people's shoes. This happened to Neville, who was splashed by it and sprouted angry red boils (PS8)
c.f. BULBADOX POWDER, FURNUNCULUS (used on Malfoy by Harry CH. 37 of GoF - doesn't play nice with the Jelly Legs jinx), WARTCAP POWDER