2.6.1. Induction of experimental contact hypersensitivity in mouse ear
For the induction of contact hypersensitivity (CHS), mice were divided into 3 groups with 5 mice per each treatment group; normal healthy control treated with PBS alone without CHS induction, treatment groups treated either with vacant gel or gel containing placenta extract. CHS was induced by painting 20l (per ear lobe) of 1% 2,4-dinitrocholorobenzene (DNCB) after stripping each ear lobe with surgical tape. Control group mice were painted with PBS after ear stripping. DNCB painting was done after every 2 days in a week for 1 month. At the end of 2 weeks, serum IgE concentration was estimated to check induction and thereafter treatment was done every day by painting 50l (per ear lobe) of vehicle (vacant gel) or gel containing placenta extract (PE group). Ear thickness was measured 24 h after each application of DNCB with calipers. To confirm the inefficacy and inertness of vehicle (vacant gel), vehicle and PBS were applied separately to DNCB-induced CHS mice. Both groups failed to enhance dermatopathological symptoms of CHS.