The auricular edema is achieved by applying 12-0- Tetradecanoil Forbol-13 Acetate (TPA), one of the components responsible for the irritating action of croton oil, into the auditory pavilion of the mouse. The inflammatory reaction consists of erythema, edema and infiltration by polymorphonuclear leukocytes. As such, eicosanoid -type mediators are freed, inducing degranulation of the mast cell.