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Metallic gold is known for its electrochemical nobility, and resulting lack of reactivity. Thus, it is usually accepted to be a non-allergenic metal.
For this reason, contact dermatitis due to gold has been rare, and difficult to prove. It was Kligman who first found that gold chloride could cause sensitization.
Fowler later initiated the use of 0.5% w/w gold sodium thiosulfate (GSTS) in petrolatum as a test preparation to determine the presence of contact allergy to gold. At present, varying concentrations of GSTS in petrolatum are in use.
Patients who are allergic to gold often present with contact dermatitis, contact stomatitis, or oral lichen planus.
Skin manifestations such as a papular pruritic rash are most commonly found on the ears, eyelids or the area around the eyes, the fingers, and the neck.
Reactions in remote areas far from contact are also possible. Gold allergy is more commonly found in women.
It has been found that one in ten patients with eczema had positive reactions when their standard patch tests included gold patch testing (as GSTS). Thus, gold is a potent sensitizer, second only to nickel sulfate.
Dental patients with gold fillings, or individuals who wear gold allergy, show an incidence of allergy that is higher than normal, which means the gold in the fillings could be a major cause of gold allergy.
At the same time, patients with contact allergy to gold have a higher chance of sensitivity to other monovalent gold salts, such as gold sodium thiomalate, as well as to nickel and cobalt.
The presence of a contact allergy to gold is confirmed by a positive patch test to GSTS, consisting of a persistent papular reaction.
The test reaction may often persist for months after the patch application. Patch size must be measured at 3 days, 1 week, and even at 3 weeks, because many reactions take a longer time than expected to appear when the patch test is used.
With intracutaneous testing, however, all reactions occur within the first week, and dermal nodules are often formed.
Percutaneous absorption of ionized gold is essential for the formation of a positive reaction.
An in vitro test for gold allergy looks for the appearance of blast transformation induced by gold salts.
Treatment of gold allergy comprises the use of local emollients and corticosteroids to suppress local allergic manifestations, as well as the treatment of any secondary bacterial infection.
Exposure to gold salts must be minimized in order to prevent future allergic reactions.