In summary, our data provide evidence for a novel action of corticosteroids: suppression of allergic inflammation through a rapid inhibitory effect on GATA-3 nuclear translocation by preferential binding to the shared nuclear import protein importin-α and by a second mechanism involving increased synthesis of MKP-1, which inhibits p38 MAPK, thus preventing the phosphorylation of GATA-3 that is necessary for nuclear translocation of GATA-3.