Hypersensitivity (to food, eg) (7)
I believe the answer is:
allergy
(Other definitions for allergy that I've seen before include "Antipathy (colloq.)" , "Hypersensitive reaction of the body to a foreign substance" , "Abnormal sensitivity to a food" , "Unfavourable reaction to pollen, certain foods etc" , "Unfavourable reaction to, say, pollen" .)