noun
also id·i·o·syn·cra·cy ˌidēəˈsiŋkrəsē, -dēoˈ-, -sink-, -rəsi
Etymology: Greek idiosynkrasia, from idio- + -synkrasia (from synkrasis action of commingling or blending — from synkerannynai to commingle, blend, from syn- + kerannynai to mingle, mix — + -ia -y) — more at crater
1. : characteristic peculiarity of habit or structure
2.
a. : a peculiarity of physical or mental constitution or temperament : a characteristic distinguishing an individual ; broadly : eccentricity
b. : individual hypersensitiveness (as to a drug or food)
anemia accompanying the use of a sulfa drug is usually considered to be due to idiosyncrasy