Several weeks ago, I received a fax from an allergist regarding a mutual patient. The patient had gone through a routine allergy skin test and some interesting results came up.

The patient tested positive for gold sodium thiosulfate which is a gold derivative used for screening of contact allergy to dental gold materials. I found these results quite surprising. We are all familiar with allergies to nickel and other base metals, but I had yet run across a patient with this allergy. I spoke to some colleagues who were also unfamiliar with any patients with gold allergies. We are taught that gold is a noble metal producing the most ideal of gingival responses.

After a quick PubMed search, I found the following article:
Investigation of contact allergy to dental metals in 206 patients.
Raap U, Stiesch M, Reh H, Kapp A, Werfel T.
Contact Dermatitis. 2009 Jun;60(6):339-43.

The authors found that out of 206 patients, 28 had positive patch tests to some dental metal. The number of positive patch test reactions was highest for gold sodium thiosulfate, palladium chloride, and nickel sulfate.

Wow! So out of dental metals, gold is one of the most common allergies. The sample size is quite small on this study. It would be interesting to see the results with a sample size of 1000 or 2000. My instinct tells me that we would see a much higher incidence of nickel allergy with a larger sample size, however those results are not evident with the smaller sample size.