Cross allergy between paranitro compounds including DNCB and chloramphenicol was studied in 42 patients. A total of 27 had been primarily sensitized to DNCB, and 15 patients with eczema exhibited a delayed‐type reaction to chloramphenicol, showing u positive patch lest. All 15 patients with chloramphenieol allergy cross reacted with chloramphenicol succinate and chloramphenicol palmitate. Three of them cross reacted with paranitrobenzoic acid, and two of these also with paradinitrobenzene. None of the 15 patients cross reacted with DNCB in acetone or DNCB in petrolatum, and none reacted to picric acid, paranitrophtnol or dinitroorthocresol. The 27 patients primarily sensitized to DNCB did not cross react with any of the paranitro compounds studied, in particular not with chloramphenicol or its salts. Thus, the study confirms the specificity of the DNCB sensitivit