Sensitization and cross-reactivity patterns of contact allergy to diisocyanates and corresponding amines: investigation of diphenylmethane-4,4′-diisocyanate, diphenylmethane-4,4′-diamine, dicyclohexylmethane-4,4′-diisocyanate, and dicylohexylmethane-4,4′-diamine

Abstract

Background: Isocyanates are used in polyurethane production. Dermal exposure to isocyanates can induce contact allergy. The most common isocyanate is diphenylmethane diisocyanate used for industrial purposes. The isomer diphenylmethane-4,4′-diisocyanate (4,4′-MDI) is used in patch testing. Diphenylmethane-4,4′-diamine (4,4′-MDA) is its corresponding amine. Concurrent reactions to 4,4′-MDI and 4,4′-MDA have been reported, as have concurrent reactions to 4,4′-MDI and dicyclohexylmethane-4,4′-diisocyanate (4,4′-DMDI). Objectives: To investigate the sensitization capacities and the cross-reactivity of 4,4′-MDI, 4,4′-MDA, 4,4′-DMDI, and dicyclohexylmethane-4,4′-diamine (4,4′-DMDA). Methods: The guinea-pig maximization test (GPMT) was used. Results: The GPMT showed sensitizing capacities for all investigated substances: 4,4′-MDI, 4,4′-MDA, 4,4′-DMDI, and 4,4′-DMDA (all p < 0.001). 4,4′-MDI-sensitized animals showed cross-reactivity to 4,4′-MDA (p < 0.001) and 4,4′-DMDI (all p < 0.05). 4,4′-MDA-sensitized animals showed cross-reactivity to 4,4′-DMDA (p = 0.008). Conclusion: All of the investigated substances were shown to be strong sensitizers. Animals sensitized to 4,4′-MDI showed cross-reactivity to 4,4′-MDA and 4,4′-DMDI, supporting previous findings in the literature. The aromatic amine 4,4′-MDA showed cross-reactivity to the aliphatic amine 4,4′-DMDA.