Skin testing with gold sodium thiomalate and gold sodium thiosulfate

Recently gold sodium thiosulfate was found to be the most common sensitizer after nickel sulfate in our routinely patch tested dermatitis patients. When patients hypertensive to gold sodium thiosulfate were tested with another monovalent gold salt, gold sodium thiomalate, at equimolar concentrations, in principle, no positive reactions were obtained. Gold sodium thiomalate is used for treatment of rheumatoid arthritis, a treatment with a high frequency of adverse skin reactions. To investigate whether the reactivity difference between the 2 gold salts was due to differences in bioavailability, some experiments were carried out. Intracutaneous tests with the 2 gold salts at equimolar concentrations yielded equivalent reactions. When the concentration of gold sodium thiomalate for epicutaneous testing was increased, all 12 gold-allergic patients reacted positively. Therefore, in our department, contact allergy to gold sodium thiomalate is probably as common as contact allergy to gold sodium thiosulfate.