3 cases of allergic contact dermatitis from industrial rubber products were investigated using a combination of patch testing in patients and chemical analysis of causative rubber products by gas chromatography (GC), GC‐mass spectrometry (GC‐MS) and high‐performance liquid chromatography (HPLC). Our studies revealed N‐isopropyl‐N′‐phenyl‐p‐phenylenediamine (IPPD), a typical rubber allergen, as a causative chemical in a case from a brand of heavy‐duty rubber gloves and a case from a black rubber ring for car manufacture, and zinc ethylphenyldithiocarbamate (ZEPC), a dithiocarbamate (DTC)‐type accelerator, as a causative chemical in a case from a brand of rubber work gloves: both IPPD and ZEPC, which showed positive patch test reactions, were confirmed in the extracts of the causative rubber products by