A 10-year Retrospective Study on Palladium Sensitivity

Olayemi Durosaro; Rokea A. el-Azhary


Dermatitis. 2009;20(4):208-213. 

In This Article


There are two key findings in our study. In the first, the frequency of palladium sensitivity in our US patch-test patients who were tested with palladium was 12.1%; a higher frequency was observed in patients with mucous membrane diseases. In the second, the incidence of co-reactivity of gold with palladium approached that of the co-reactivity of nickel.

Our frequency was higher than the sensitization rate found in European studies, which ranged between 8% and 10%, but was similar to the sensitization rate in the study from Israel, in which the investigators reported a rate of 13%.[9] The use of palladium in dental alloys in the United States is reportedly greater than its use in Europe,[2] which might account for the difference in sensitivity between European studies and our US-based study. However, to our knowledge, there is no indication of an increased use of palladium in jewelry produced in the United States as compared to Europe.[4] Currently, there are no reports in the medical literature on the frequency of palladium sensitivity in a US patch-test population for comparison with our results.

No relevance data were available from any of the published series on palladium.[5,6,8–10,13] Although we had a relevance of 54.7% as extracted from the histories, we found it difficult to verify this relevance in a large series of patients retrospectively, similar to other investigators. In one case in our series, the clinician tested the oral amalgam adjacent to the lichenoid lesions and found it to contain palladium and no gold. That patient had reaction to both metals; therefore, the palladium allergy was deemed valid and relevant. This difficulty of determining relevance is particularly true for a metal such as palladium, which is present in various concentrations and electrochemical configurations in many alloys[3,14,15] and which co-reacts with many other metals. In addition, palladium is used in dentistry in the cores of crowns; hence, it may not be directly visible to the examining physician as a silver-colored filling. The solubility of palladium and other noble metals in the alloy has been the subject of extensive research and depends on the method by which the alloy is prepared, as well as the length of time the alloy is in the mouth and in contact with saliva, leading to corrosion.[14,15] Garhammer and colleagues reported that deposition of metals (including gold, silver, and palladium) was noted in biopsy samples of affected mucosal skin directly adjacent to dental alloy.[16] In 84% of cases, the investigators found the metal from lesional mucosa as opposed to unaffected mucosa. This finding indicated that metals do leach out of the alloy and may have a direct role in the skin disease. Because the patients may have had dental alloy from different manufacturers and may have had it applied at different times in their lives, the relevance data extracted from the charts may not be dependable. True relevance can be determined only by having information on the composition of the dental alloy (or obtaining a sample of the amalgam for analysis to confirm the presence of the metal) and by having an accurate history that tells when the alloy was placed in the mouth, neither of which were available to us in this study.

Exclusive palladium-only metal sensitivity is a rare phenomenon, and it is thought that these isolated cases may help determine the true allergenic potential of the metal.[9] In our study, 9 (8.2%) of 110 patients had palladium metal monosensitivity. Of these 9 patients, 4 had preventive patch tests and had no dermatologic complaints at the time of the patch testing. The other 5 patients consisted of 4 with oral involvement and 1 with skin dermatitis. A study in Italy reported a 7.2% (17 of 236 patients) occurrence of palladium monosensitivity.[8] Only one patient in this study had an oral symptom, noted to be burning mouth, and the other 16 patients had dermatitis. Orion and colleagues reported a single dermatitis case in the Israeli study but did not specify the location of the dermatitis.[9]

The etiology of BMS is unknown but is thought to be multifactorial, possibly involving local and systemic factors. There have been controversial suggestions that contact hypersensitivity might have a role in BMS.[17] In a study by Lamey and colleagues, as many as 65% of patients with positive patch-test reactions were reported to have intermittent BMS.[18] A study by Dal Sacco and colleagues showed that 13% of patients with BMS had a relevant contact hypersensitivity.[17] No studies in the literature have specifically linked palladium to the etiology of BMS. In a recent study by Torgerson and colleagues, 9.7% of 196 patients with BMS had patch-test results that were positive for palladium.[19] Our study showed that 13.2% of palladium-sensitive patients had BMS, 1 patient having monosensitization to palladium. These findings raise the question of whether palladium sensitivity is related to BMS. Focused studies are needed to validate this association.

Our study showed that 15.1% of patients with sensitivity to palladium had oral lichen planus; of these patients, 6.3% had monosensitization to palladium. We found no US studies that reported the frequency of lichen planus in regard to palladium sensitivity; however, a study on palladium contact sensitivity indicated that lichenoid reactions are one of the common manifestations of palladium sensitivity in the clinical setting.[10] A recent study from the Czech Republic noted a frequency of 12.9% for lichenoid reactions in the oral mucosa for palladium-sensitive patients, which ranked second to mercury and higher than gold in frequency.[20]

Nickel allergy was found in 57.0% of patients sensitized to palladium. Our results are in line with those of previous studies, which have shown a co-reactivity as high as 94.1% between the two metals.[1,9,13,21] This co-reactivity is thought to be either a cross-reaction (because both metals belong to group VIII of the periodic table)[22,23] or a combined sensitization to both metals.[10]

The high incidence of co-reactivity of gold with palladium in our study has not been previously described. These two metals are far from each other in the periodic table, but both have been reported to cause lichenoid eruptions.[1,24] In the oral mucosa, we found high gold co-reactivity, which is most likely related to the individual allergenicity of the two noble metals being present in the same alloy (either in jewelry or in oral dental alloys).

The high female preponderance of 92% in our study was noted in all groups of palladium-sensitive patients. The female preponderance in patients with BMS has been previously documented but is somewhat controversial in the other groups.[19,25–28]

The limitations of our study include the retrospective nature of data retrieval and the difficulty in assigning relevance. In addition, our clinic is a referral center, and our patients may not be reflective of the general population.


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