Patch testing with a large series of metal allergens: Findings from more than 1,000 patients in one decade at Mayo Clinic

Background: The standard allergen series used in patch testing contains metals that most commonly cause allergic contact dermatitis, but testing with additional metal allergens is warranted for select patients. Objective: To report our experience with patch testing of metals. Methods: We retrospectively analyzed outcomes of 1,112 patients suspected of having metal allergies. Patients were seen from January 1, 2000, through December 31, 2009. Patch testing was performed with 42 metal preparations (6 in the standard series, 36 in the metal series). Results: Patch testing most commonly was performed for patients with oral disease (almost half the patients), hand dermatitis, generalized dermatitis, and dermatitis affecting the lips, legs, arms, trunk, or face. At least one positive reaction was reported for 633 patients (57%). Metals with the highest allergic patch-test reaction rates were nickel, gold, manganese, palladium, cobalt, Ticonium, mercury, beryllium, chromium, and silver. Metals causing no allergic patch-test reactions were titanium, Vitallium, and aluminum powder. Metals with extremely low rates of allergic patch-test reactions included zinc, ferric chloride, and tin. Reaction rates varied depending on metal salt, concentration, and timing of readings. Conclusion: Many metals not in the standard series were associated with allergic patch-test reactions. The many questions raised by these findings, concerning patch testing with individual metals, will be the subject of future studies.