Although beneficial effects of placenta extract from various animals have been noticed for a long time, the definitive action mechanism was not clear. In this study we have shown the potent immunomodulatory function of porcine PE in experimental contact hypersensitivity. Porcine PE treatment inhibited macrophage activation and production of TNF-α in vitro. Topical application of porcine PE suppressed CHS progression by down-regulating the key cytokines of CHS pathogenesis such as IL-1β, TNF-α, IL-12 and IL-17. In addition, PE treatment reduced serum IgE levels and IL-4 expression. These results suggest that PE may exert its anti-inflammatory effect by reducing the hyper-activation of antigen presenting cells, which in turn decreased production of inflammatory cytokines by T helper cells and other lymphocytes. Identification of the active compounds responsible for immunomodulatory activity of porcine PE in CHS progression will potentiate its use. Currently, we are in the process of identifying and comparing the effects of the individual components of porcine PE with the whole extract. Although, we still need to define the anti-inflammatory mediators and exact components of the extract responsible for this property, porcine PE does exert a beneficial role in decreasing or modulating the severity of the inflammatory responses associated with CHS and thereafter.