Intradermal testing in doubtful cases of contact allergy to metals

Among 1670 consecutively patch tested patients an intradermal test with chromium, cobalt and nickel was added in 66 cases. There were three indications for intradermal testing: 1) the patch test reaction at 72 h was difficult to interpret; among 49 patients with one or more doubtful reactions a metal allergy was confirmed in 24 and rejected in 54. 2) ten patients with a negative patch test in spite of a positive history of metal allergy; among these, one was positive to cobalt, two to nickel and the other seven negative. 3) seven patients checked for a previously diagnosed allergy; a metal allergy was confirmed in four. Intradermal testing is recommended for confirmation of doubtful patch test reactions, particularly to disclose false positive reactions to metals.