Nickel allergy and nickel-containing dental alloys.

Test pieces from five cobalt-chromium casting alloys intended for use in removable partial dentures were attached to the skin of 10 women with known allergy to nickel. Patch tests were also performed with nickel and cobalt salts. Nine of the 10 women showed clear-cut or strong patch test reactions to the alloy with 7% nickel, one patient also to one of the other alloys (less than 1% nickel). In five patients with contact allergy reactions to both nickel and cobalt salts mild or marked responses to some of the other alloys were observed. Corresponding observations were made in three out of the five patients with contact allergy reactions to nickel salt but not cobalt salt.