BACKGROUND: In Spring 1992, an epidemic outbreak of papular and follicular rashes caused by a new line of cosmetics occurred throughout Switzerland. OBJECTIVE: Epidemiological and clinical data were collected in order to identify the offending agent and to specify the pathophysiological mechanisms. METHODS: The data concerning 263 patients seen by dermatologists plus 642 additional cases directly reported by consumers to the manufacturer were analyzed. Seventy-seven patients were patch-tested, 26 extensively, and 15 performed a repeated open application test for a duration of 4 weeks. Control patch and use tests were performed in 73 and 25 patients, respectively. The results were analyzed statistically. In addition, 12 skin biopsies were performed for histological examination. Biochemical studies on the cosmetics (final products and offending ingredient) supplemented the clinical studies. RESULTS: The lesions were mainly papular and follicular, widely distributed, with pronounced pruritus, which was aggravated by sweating or heat exposure, and were long lasting. In a few cases, the papules were located on intensely erythematous, well-defined plaques, suggesting irritation rather than allergy. Both immediate and delayed onsets of the lesions were observed. Skin biopsies showed signs of folliculitis and perifolliculitis with little alteration of the interfollicular epidermis. Patch and use testing disclosed vitamin E linoleate (a mixture of tocopheryl esters, mainly tocopheryl linoleate) as the offending agent. An in vitro time-dependent formation of oxidative products under storage or oxidation-stimulating conditions was observed. CONCLUSION: Though vitamin E esters have been widely and safely used for decades in dermatological preparations and in cosmetics, vitamin E linoleate was the cause of about 1,000 cases of unusual papular mainly follicular contact dermatitis. Oxidized vitamin E derivatives could act in vivo as haptens and/or irritants, possibly with synergistic effects.