Antiallergic and antipsoriatic effects of Korean Red Ginseng (KRG, steamed root of Panax ginseng CA Meyer, Family Araliaceae) were measured. Orally administered KRG water extract potently inhibited passive cutaneous anaphylaxis (PCA). KRG water extract also showed the potent inhibition in oxazolone-induced mouse dermatitis, and suppressed mouse ear swelling by 39% at 16 days at a dose of 0.1 %. KRG water extract reduced the levels of mRNA of cyclooxygenase (COX)-2, IL-1β, TNF-α and IFN-γ increased in oxazolone-applied mouse ears, however, did not inhibit that of IL-4. KRG water extract also inhibited iNOS and COX-2 mRNA expression level of RAW264.7 cell induced by lipopolysaccharide. Based on these findings, we suggest that KRG can improve atopic and contact dermatitis by the regulation of IL-1β and TNF-α produced by macrophage cells and interferon-γ produced by Th1 cells.