Patch testing with substances not included in the standard series.

During a 5-year period, 3664 consecutive patients were patch tested in a private dermatology practice with the Standard Series of the International Contact Dermatitis Research Group (ICDRG). 454 of these were tested with one or more additional substances which were suspected of having caused their dermatitis. 194 of the 454 patients had positive reactions to one or more of the additional substances. Most of these reactions were of current relevance, and in only 25% of the patients could the allergies have been predicted by the use of the Standard Series alone. In approximately 50% of the patients, the reactions to additional substances could be traced to occupational sources.