Abstract
Background:Isocyanates are mainly considered respiratory allergens but can also cause contact allergy. Diphenylmethane-4,4′-diamine (4,4′-MDA) has been considered a marker for diphenylmethane-4,4′-diisocyanate (4,4′-MDI) contact allergy. Furthermore, overrepresentation of positive patch-test reactions top-phenylenediamine (PPD) in 4,4′-MDA positive patients have been reported.Objectives:To investigate the sensitizing capacities of toluene-2,4-diisocyanate (2,4-TDI) and PPD and the cross-reactivity of 4,4′-MDA, 2,4-TDI, dicyclohexylmethane-4,4′-diamine (4,4′-DMDA), dicyclohexylmethane-4,4′-diisocyanate (4,4′-DMDI), 4,4′-MDI and PPD.Methods:The Guinea Pig Maximization Test (GPMT) was used.Results:PPD was shown to be a strong sensitizer (p<0.001). Animals sensitized to PPD showed cross-reactivity to 4,4′-MDA (p<0.001). Animals sensitized to 4,4′-MDA did not show cross-reactivity to PPD. 8 animals sensitized to 2,4-TDI were sacrificed due to toxic reactions at the induction site and could thus not be fully evaluated.Conclusion:PPD was shown to be a strong sensitizer. However, it cannot be used as a marker for isocyanate contact allergy. On the other hand, positive reactions to 4,4′-MDA could indicate a PPD allergy. The intradermal induction concentration of 2,4-TDI (0.70% w/v) can induce strong local toxic reactions in guinea-pigs and should be lowered.
Highlights
Diisocyanates are reactive compounds used in the production of polyurethane (PUR)
Allergic contact dermatitis caused by isocyanates is mainly considered to be an occupational problem and consumers are rarely exposed to isocyanates
Animals sensitized to PPD showed cross-reactivity to 4,4′-MDA (p
Summary
Diisocyanates are reactive compounds used in the production of polyurethane (PUR). PUR products are widely used and can be found in applications stretching from rigid and flexible foams to coatings, elastomers (rubber) and adhesives [1]. The structurally related amine, diphenylmethane-4,4′-diamine (4,4′-MDA), has been suggested as a marker for 4,4′-MDI allergy [9, 10] since several reports show that workers exposed to MDI react positively to 4,4′-MDA but not to 4,4′-MDI [9 - 11]. This was confirmed in a recent animal study where the crossreactivity patterns of 4,4′-MDI, 4,4′-MDA, dicyclohexylmethane-4,4′-diisocyanate (4,4′-DMDI) and dicylohexylmethane-4,4′-diamine (4,4′-DMDA) were investigated [12]. Overrepresentation of positive patch-test reactions to p-phenylenediamine (PPD) in 4,4′-MDA positive patients have been reported
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