Occupational airborne contact urticaria and asthma: simultaneous immediate and delayed allergy to diphenylmethane-4,4’-diisocyanate

Exposure to isocyanates may cause health risks, mainly in occupational environment. The most common disease is asthma, while allergic or irritant contact dermatitis, contact urticaria and systemic toxicity have been rarely reported. In this article the 1st case of concomitant type I and type IV sensitivities to diphenylmethane-4,49-diisocyanate (MDI) is described. A 52-year-old non-atopic man, employed in a chemical factory manufacturing adhesives, consulted us for breathing difficulties and urticaria on his face. The symptoms developed few minutes after every working exposure to Isonate M143® glue in his working environment. This product contains MDI. Patch testing with Isonate M143® 2% pet. showed an immediate urticarial type positive reaction. Eczematous reactions to Isonate M143® 1% and 0.5% and to MDI were observed. Quantification of isocyanate specific immunoglobulin E (IgE) by fluoroenzymeimmunoassay showed class 3 positivity to MDI (11.7 kU/l) and to 1,6-hexamethylenediisocyanate (HDI) (4.76 kU/l) and class 2 positivity to toluenediisocyanate (TDI) (0.88 kU/l). The patient was never been occupationally exposed to HDI and TDI. Provocation test simulating working duties with Isonate M143® was also positive. Isocyanates are chemicals increasingly used in the plastic industry. These chemicals are divided in aromatic (MDI and TDI) and aliphatic isocyanates (HDI). We suppose that in our patient a Tcell-mediated immune response could be considered to be involved in diisocyanate asthma, while immediate positive patch test and detection of serum MDI–IgE antibodies could justify contact urticaria.