The immunoglobulin involved in type I hypersensitivity reaction is:

Type I or anaphylactic or reagin dependent hypersensitivity reactions are mediated by IgE antibodies. Type II or cytotoxic reactions are mediated by IgG and rarely by IgM. IgG, IgM and leucocytes are involved in Type III or immune complex reactions. T cells, lymphokines and macrophages are involved in Type IV or delayed hypersensitivity reactions.Ref: Pathologic Basis Of Disease, Robbins, 6th Edition, Page 172; 7th/207; Chandrasoma Taylor 2nd Edition, Page 103; Textbook of Microbiology, Ananthanarayan and Paniker, 7th Edition, Chapter 18, Page 160.