Percutaneous absorption of gold sodium thiosulfate used for patch testing

Contact allergy to gold has been shown to be correlated to wearing of golden jewellery as well as to the presence of dental gold. The prerequisite for sensitization and elicitation of an allergic contact dermatitis to gold is ionization and percutaneous absorption of the allergen. The present study was undertaken with the aim to demonstrate gold in blood after an occlusive patch testing with gold sodium thiosulfate (GSTS). Patients were patch tested with GSTS 0.5, 2.0 and 5.0% in petrolatum. Venous blood was sampled before testing as well as on day 3 (D3) or day 7 (D7). Blood gold levels were analysed by inductively coupled plasma mass spectrometry. In all 66 patients, the blood level of gold was significantly higher in the 2nd blood sample than in the 1st (median 0.34 versus 0.03 micro g/l). The increase was similar in patients allergic and not allergic to gold. There was no difference between gold levels on D3 and on D7 after epicutaneous application. Presumably, other allergens may also be taken up in blood during patch testing.