A probable role for vaccines containing thimerosal in thimerosal hypersensitivity.

We patch tested 141 patients with 0.05% aq. thimerosal and 222 patients with 0.05% aq. mercuric chloride, including 63 children. The frequency of positive patch test reactions to thimerosal was 16.3%. There was a marked preponderance in the young age groups after vaccination, while none of 36 infants (aged 3-48 months) reacted to thimerosal. Positive reactions to mercuric chloride were found in 23 (10.4%) of 222 patients. We also sensitized guinea pigs with diphtheria-pertussis-tetanus (DPT) vaccine containing 0.01% thimerosal and succeeded in inducing hypersensitivity to thimerosal. From patch testing in humans and animal experiments, it is suggested that 0.01% thimerosal in vaccines can sensitize children, and that hypersensitivity to thimerosal is due to the thiosalicylic part of the molecule and correlates with photosensitivity to piroxicam.