AU idea where Character A is madly in love with Character B but becomes allergic to them and only them.
Up to you if Character B reciprocates their feelings, whether Character A is able to undergo any sort of immunotherapy and/or take meds to help with the symptoms and tolerate being around Character B again, what the extent of the allergy is, and whether Character B ever finds out about the allergy and/or the true reason Character A is suddenly avoiding them.
Variation: Character A is a hero and Character B is a villain, and Character A is supposed to capture Character B and bring them to justice. But that's going to be very difficult now with this allergy…especially once Character B finds out about the allergy.















