"Fever Fudge ... no one's seen that yet -"
"Well, yeah ... your temperature'll go right up."
"But you get these massive pus-filled boils, too ... and we haven't worked out how to get rid of them yet."
"... they're not in a place we generally display to the public."
"But they make sitting on a broom a right pain in the --"
-- The Weasley Twins (OP18)
One selection in the Weasley Twins’ Skiving Snackboxes (OP6).
- Eating Fever Fudge causes your temperature to go up, and pustules to form in a delicate place (making broom-sitting uncomfortable) (OP18).
- Essence of Murtlap clears up the boils from Fever Fudge, which the Twins learned from Lee Jordan, who learned it from Harry, who learned it from Hermione after his painful detention with Dolores Umbridge (OP15,OP25,OP26).