Contact dermatitis caused by a new rubber compound detected in canvas shoes

In 2015 and 2016, female patients in Flanders consulted a dermatologist because they developed skin lesions after wearing a specific brand of canvas shoes.

To identify the culprit allergen in the shoes.

Eighteen young females aged 14-22 years presented with itching and erythematous to purple-coloured eczematous lesions on both feet. They were patch tested by 10 dermatologists with the European baseline series. Some patients underwent testing with additional series. Pieces of the shoe fabrics were tested in 11 of 18 patients. Chemical analysis of the shoe materials was performed. Finally, patients were tested with a thin-layer chromatogram of the shoe extracts and dilutions of the suspected rubber compound.

All 18 patients showed positive reactions to thiuram mix. Ten of 11 patients reacted to a piece of shoe fabric. Chemical analysis showed the presence of dimethylthiocarbamylbenzothiazole sulfide (DMTBS). No thiurams were detected. Four patients tested with the chromatogram developed positive reactions to DMTBS. Positive reactions to low concentrations were observed in the 4 patients tested with a DMTBS dilution series; one patient reacted to 0.00001% in acetone.

DMTBS, the culprit allergen, is a component formed during rubber vulcanization that probably cross-reacts with the thiuram mix.