Since I'm not sure how Tycho and Gabe would feel about Miss Mumpy reproducing their wonderful comic, I am putting a link here to one of their new installments "Men Are From Krypton". This ranks up their with one of my personal favorites "Pain Dot Com".
The brilliance of MAFK is that this is exactly what it is like when you have food allergies. The Superman analogy is perfect. If you have a food allergy (Superman) and eat even a trace of that food (kryptonite), then you either become very sick (best case scenario, lots of fun on a dinner date) or you die (which is technically the worst case scenario but when you are bowing to the porcelain god and feeling like you are being turned inside out against your will then the latter option does have it's appeal).
**While on the topic there is a brilliant short-story in the collection Between Myself and Them: Stories of Disability and Difference, one of Mumpy's picks for the Best of 2005, Something Like a Vampire by Sara Scharf which draws the Superman vs Kryptonite and Vampire vs Garlic analogies to how life altering it can be dealing with food allergies.