Atopy in hypersensitivity is -

Type I hypersensitivity occurs in two forms : 1. Anaphylaxis 2. Atopv → → Acute, potentially fatal, systemic. Chronic. Nonfatal. Localized. Remember  Mast cells are the most important cells in type 1 hypersensitivity. O Eosinophils are the most important cells in the late phase reaction of type I hypersensitivity,  Histamine is the most important mediator in type 1 hypersensitivity.  1L-4 is particularly important, it is essential for turning on IgE secreening B cells.  PAF is the most important cytokine in the initiation of late phase reaction. Most potent eosinophilic activating cytokine is 1L-5.