Background Metallic allergens such as nickel are among the most common causes of allergic contact dermatitis (ACD), but frequencies of contact dermatitis to these allergens may vary in different areas.
Objectives This study aimed to determine the frequencies of ACD caused by three common metallic allergens: nickel sulfate; potassium dichromate; and cobalt chloride.
Methods Data for 1137 patients with clinical diagnoses of contact dermatitis and/or atopic dermatitis evaluated by patch testing in Iran during a 5-year period were retrospectively studied to establish the frequencies of hypersensitivity to these metallic allergens.
Results A total of 313 patients (27.5%) gave positive patch test results for at least one metallic allergen. Allergy to nickel (229 cases, 20.0%) was the most commonly observed, followed by allergy to cobalt (90 cases, 8.0%) and allergy to chromium (70 cases, 6.2%). Nickel allergy was significantly more frequent in females and in subjects aged <40 years, whereas chromium hypersensitivity was more common in males and in subjects aged >40 years. Sensitivity to nickel or chromium was a risk factor for cobalt allergy.
Conclusions Nickel was most commonly identified as a metallic allergen in Iran and tended to affect women aged <40 years. Regulations pertaining to nickel release may decrease the frequency of nickel hypersensitivity in Iran.