Background. Dimethyl fumarate (DMF) has been identified as being responsible for an outbreak of shoe contact dermatitis in Europe. All reported cases to date have involved the dorsa of the toes and the dorsa of the feet, sometimes in association with other areas.
Objectives. To establish a correlation between the site of the lesions and the concentration of DMF in different parts of the footwear from patients suffering from shoe contact dermatitis.
Methods. We performed a retrospective study of 8 patients with shoe contact dermatitis caused by DMF. Clinical data and patch test results obtained with DMF were recorded. The contents of DMF in different parts of eight samples of shoes involved were analysed with gas chromatography–mass spectrometry.
Results. The chemical analysis of all samples studied showed the presence of DMF, both in the uppers and the soles of the shoes. A clinical–analytical correlation was found in all cases. The presence of DMF in a child's boot was detected 1 year after withdrawal of the sachet with DMF from the shoe box.
Conclusions. A correlation exists between the concentrations of DMF in the different parts of the shoe and the localization of the lesions. Although DMF is a volatile substance, it can remain impregnated in shoes for a long period of time.