Long-term trend in patch test reactions: a 32-year statistical overview (1970-2002), part II.

Allergic contact dermatitis remains an important problem worldwide. The objective of this study was to analyze patch test positivity trends of the North American Contact Dermatitis Group. Publications from 1970 to 2002 were reviewed and re-analyzed. Statistical significance was determined with a Cochran-Armitage trend test. We observed a significant increase in positive reactions with carbamates, balsam of Peru, thimerosal, formaldehyde, imidazolidinyl urea, and methyldibromoglutaronitrile. The rates of positive reactions to Dimethylol dimethyl (DMDM) hydantoin, diazolidinyl urea, and methylchloroisothiazolone/methylisothiazolone remained unchanged. We showed a significant decrease in positive reactions for all other allergens. These data provide challenges in public health--for industry, government, and medicine--to decrease the frequency of allergic contact dermatitis. However, the complexities of evaluating a 32-year analysis are numerous, so the data should be interpreted with caution and within the context of this work.