IGHE and IgE responsiveness, atopic: In contrast with IgE-mediated immediate drug hypersensitivity reactions (IDHRs) (type I hypersensitivity reaction—IgE mediated—, according to Gell and Coombs classification system of immune reaction), which occur mostly within one hour after the drug exposure, NIDHRs (type II—IgG/IgM cytotoxic reactions –, type III—IgM/IgG immune complexes mediated—and type IV—T-cell mediated—hypersensitivity reactions) are antibody or cell-mediated reactions and arise usually days or weeks after initial drug administration.