-ergic as in sentences like Y is Xergic denotes that Y has the property of being sensitive to X or that Y produces X. In simple terms, it means that the noun does something with x. In my field of study, this os true for e.g. dopaminergic-, serotonergic-, and glutamatergic neurons which are neurons that are sensitive to these respective neurotransmitters and/or releases them.
But the word allergic seems to denote only a sensitivity to allergens but not a production of allergens? An allergic person does not release pollen. Is the word allergic too general and therefore a misnomer?