Allergic inflammation

[5] The reaction is caused by the release of histamine and mast cell granule proteins by a process called degranulation, as well as the production of leukotrienes, prostaglandins and cytokines, by mast cells following the cross-linking of allergen specific IgE molecules bound to mast cell FcεRI receptors.

[6] The late phase of a Type 1 reaction (which develops 8–12 hours and is mediated by mast cells)[5] should not be confused with delayed hypersensitivity Type IV allergic reaction (which takes 48–72 hours to develop and is mediated by T cells).

[7] The products of the early phase reaction include chemokines and molecules that act on endothelial cells and cause them to express Intercellular adhesion molecule (such as vascular cell adhesion molecule and selectins), which together result in the recruitment and activation of leukocytes from the blood into the site of the allergic reaction.

[3] Typically, the infiltrating cells observed in allergic reactions contain a high proportion of lymphocytes, and especially, of eosinophils.

The recruited eosinophils will degranulate releasing a number of cytotoxic molecules (including Major Basic Protein and eosinophil peroxidase) as well as produce a number of cytokines such as IL-5.