 The response is a classical example of delayed-type hypersensitivity reaction (DTH), a type IV of hypersensitivities.T cells and myeloid cells are attracted to the site of reaction in the timeframe of 1-3 days and generate local inflammation.The reaction is read by measuring the diameter of induration (palpable raised, hardened area) across the forearm (perpendicular to the long axis) in millimeters.