The Bone Chillers episode where their lunchlady gets replace by someone feeding them food with larvae that can be thrown up if they consume mustard also left a mark but only for a matter of days; I remember foregoing ketchup and getting mustard on my school lunch, the next day. I think I was in elementary school, at the time.

https://www.reddit.com/r/ObscureMedia/comments/mdsdbi/bone_chillers_1996_abc_saturday_morning_kids_show/, for those curious.