TNF and urticaria: It is due to release of histamine, PGD2,[19] leukotrienes, platelet activating factor,[20] TNFα, autoantibodies like IgE and IgM has been recorded.[21] Delayed pressure urticaria was diagnosed in 2% as in the literature and is estimated to be between 2-5% and is due to the release of chemo attractant factors with the up-regulation of vascular adhesion molecules, E-selectin and VCAM 1.[22]