Forty-two cases of contact sensitivity to N-isopropyl-N'-phenylparaphenylenediamine (IPPD), an amine antiozonant used in rubber manufacture, were collated from several firms and plants dealing with tyres. Ten motor car tyres manufactured by eight different firms all induce sensitivity reactions in seven subjects allergic to IPPD. Clinical cross-reaction tests show that 100% of the subjects sensitive to IPPD are also sensitive to N-phenyl-N'-cyclohexy-paraphenylenediamine (CPPD), another amine antiozonant, and 37% to paraphenylenediamine (PPD). The various types of tyres were analyzed by gas chromatography and then by infra-red and thin-layer chromatography where necessary. None of the 12 tyres examined was found to be free from aromatic amines. Test reactions carried out with various automobile accessories on subjects allergic to IPPD in tyres gave positive results precisely in those cases where the articles contained IPPD. The authors then studied occupational sensitivity to N-dimethyl-1,3 butyl-N'-phenylparaphenylenediamine (DMPPD), a rubber antiozonant purported to be non-sensitizing and marketed in the United States. The The DMPPD tests were positive for all the IPPD-allergic patients tested; there is no doubt as to the allergenic nature of DMPPD. The irritant and sensitizing potentials of the four amines in question were tested in laboratory animals: PPD proved to be the most allergenic product, IPPD the least allergenic, and DMPPD and CPPD seem to give identical results. All these products produce positive cross-reactions in varying degrees of severity.

During 1972-1984, 13 cases of allergy to safety shoes were found. It generally affects young men. The allergens are very different from those in other types of shoe. The presence of mercaptobenzothiazole and dibenzothiazyl disulfide detected in some nonwoven materials is worthy of note.

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