THIMEROSAL POSITIVITIES - THE ROLE OF ORGANOMERCURY ALKYL-COMPOUNDS

Contact allergy to thimerosal (TH) has not been considered a marker fo r mercury allergy, since there is a low degree of cross-sensitivity to inorganic as well as to organic mercury salts. 40 subjects, who previ ously gave a positive patch test reaction only to thimerosal 0.1% pet. (Hermal), when simultaneously repatch-tested to solutions containing TH, mersalyl acid, p-amino-phenylmercuric acid, mercuric acetate and t hiosalicylic acid, respectively, gave positive reactions only to TH. 3 6 out of 40 subjects were divided into 2 groups of 18 subjects and sim ultaneously repatch-tested to solutions containing TH, methylmercury c hloride (MeHgCl), thiosalicylic acid, and, ethylmercury chloride (EtHg Cl), respectively. EtHgCl was tested in the Ist group at 0.031% and in the 2nd group at 0.015%. The results showed that all subjects gave co ncomitant positive reactions to TH, EtHgCl and MeHgCl. EtHgCl 0.031% g ave a higher number of +++ reactions than EtHgCl 0.015%, underlining t he role of the solvent in these reactions. Patch test results in 300 c onsecutive patients to a standard series, to which MeHgCl was added, s howed that MeHgCl and TH were never able to give isolated positive rea ctions, and that the concomitant positive reactions occurred in only 3 .6% of subjects. In conclusion, our data seem to suggest that the posi tive reactions to TH found in our patients were due to EtHgCl, and tha t the structural similarities with MeHgCl were so close that the skin reacted against each as if they were identical.