In addition, quercetin (3) and kaempferol (4) also inhibited PLCγ and PKC pathways of the IgE-mediated allergic reaction by reducing the expression of 5-lipoxygenase, cyclooxygenase-2 and the production of leukotriene B4 and prostaglandin E2 [43]. Here, PTGS2 is linked to allergic disease.