Patch test reactions to Biobans in metalworkers are often weak and not reproducible

Contact allergy to the industrial preservative group of Biobans has been reported in individual cases. We have performed a prospective study on 408 metalworkers who were tested with 6 different Biobans, formaldehyde and 5 other preservatives. Furthermore, retesting was performed after a time interval of 6 months to 4 years. The test results were also compared with those of the multicentric data provided by the Information Network of Departments of Dermatology in Germany and Austria (IVDK), particularly with regard to cross-reactivity between the various Biobans and formaldehyde. In 408 metalworkers 14 (3.4%) showed positive reactions to Biobans (2.2% P 1487, 2.0% CS 1246, 1.5% CS 1135), the majority being + reactions. On retesting 10 patients, the reactions were confirmed in only 2 cases (P 1487 and CS 1135). 4 patients showed positive reactions to 3 Biobans (P 1487, CS 1135, CS 1246), while 9 patients had only solitary sensitizations. Concomitant sensitization to formaldehyde was present in 5 out of 10 patients, being reproducible in 3 of them. In the IVDK data, sensitization prevalence in 3400 patients ranged from 1.8% (P 1487) to 0.8% (CS 1246). A high proportion of doubtful or irritant reactions as well as weak + reactions was observed. Cross-reactivity between the various Biobans was low, moderate agreement being calculated for CS 1135 and CS 1246 (kappa coefficient 0.43). The consensus pattern between formaldehyde and the tested Biobans was even lower. In conclusion, patch test reactions to Biobans are not rare among metalworkers but are often weak and not reproducible. Simultaneous reactivity to various Biobans and formaldehyde may be due to cross-reactivity or cosensitization from common exposure.