Diaminodiphenylmethane (DDM): frequency of sensitization, clinical relevance and concomitant positive reactions.

Diaminodiphenylmethane (DDM) is an aromatic diamine used in the manufacture of rubber, plastics, diisocyanates, dyes and adhesives. It may cross-react with para-(amino)compounds. Allergic patch test reactions to DDM are relatively frequent, but their relevance is often difficult to detect. We report our experience in 6809 patients (4589 female, 2220 male, mean age 39.9+/-17.8 years) with suspected contact dermatitis patch tested during the period 1997-1999 by the North-East Italy Contact Dermatitis Group (NEICDG). A positive patch test to DDM was detected in 132 (1.9%) patients (88 female, 44 male, mean age 49.5+/-16.2 years). Eczema was mostly localized on the hands. The relevance was detected in 31 patients. A logistic regression analysis showed an association with patient's age (odds ratio 5.4 for age 30-59 years), absence of atopic diseases (odds ratio 3.1) and presence of leg ulcer (odds ratio 5). We found a highly significant correlation (p<0.001) between sensitivity to DDM and to para-phenylenediamine, Disperse Yellow 3, cobalt chloride, fragrance mix, benzocaine, paraben mix and primin. Positive patch test results to DDM were relatively frequent. The difficulty in detecting the relevance of these sensitizations may be related to the surprisingly high frequency of concomitant positive reactions to other allergens.