Guinea pigs doubly sensitized to 2,4-dinitrochlorobenzene (DNCB) and oxazolone (OX) were tested with DNCB, OX and croton oil and retested by epicutaneous application of DNCB and OX at the sites of prior contact reaction at the various intervals following skin testing. Antigen specificity of retest reaction to DNCB was demonstrated when retest of DNCB was performed 21 and 28 days after the skin testing. The significance of the findings is discussed
