Long-lasting patch reactions to gold sodium thiosulfate occurs frequently in healthy volunteers.

In a skin irritancy study in healthy volunteers with 3 metal salts, aqueous gold sodium thiosulfate (GSTS) in a dilution series caused unexpectedly frequent and strong patch test reactions on volar forearm skin in 22 of 31 participants (71%). The reactions showed morphological features consistent with a contact allergic reaction, and the crescendo type of the response speaks in favour of an allergic nature. Further, 8 of the 31 (26%) developed long-lasting test reactions. A follow-up interview among 28/31 participants 10 years later showed that none had experienced long-term consequences in the form of skin and/or mucosal complaints related to exposure to gold items. The results indicate that inclusion of GSTS in routine patch testing may cause problems regarding interpretation and clinical relevance of positive GSTS patch tests, which fulfil the clinical criteria of a contact allergy.