Moreover, IL-9 has also been implicated as a key cytokine for allergic response to foods and IL-9 was the highest differentially expressed gene in peanut-activated memory CD4+ T cells from peanut-allergic children comparing with those from children without peanut allergy [64,71] while IL-9 was also secreted by PBMCs from egg-allergic children but not from non-allergic children after stimulation with egg white protein [64,78]. This evidence concerns the gene IL9 and peanut allergic reaction.