S2, E16: Melinda (guest star Michelle Trachtenberg), a rebellious teenage girl who is immunocompromised as a result of medications she’s taking after a heart transplant, has a severe allergic reaction and goes into shock despite living in a "clean" room. House and the team step in to figure out exactly what caused the reaction, but end up playing referee between Melinda, her overprotective mother (guest star Mel Harris) and her boyfriend.