The impact of various patient factors on contact allergy to nickel, cobalt, and chromate.

Background: Positive patch-test results to nickel, cobalt, and chromate alone and in combinations with one another are well known to occur. Patient factors that may play a role in isolated and concurrent sensitization to these allergens have not been studied in the US population.
Objective: We sought to determine the prevalence of isolated and concurrent nickel, cobalt, and chromate sensitizations and to investigate the impact of various patient factors on their development.
Methods: A retrospective analysis was carried out on patch-test data of 1187 patients evaluated at one US center from January 1, 1995, to December 31, 2004, 208 of whom had a positive reaction to at least one metal. Statistical analyses to evaluate associations of metal contact allergy with patient factors were performed using the chi(2) test and conditional odds ratio.
Results: All patients who reacted to metal had increased odds of cosensitization to another metal. Patients who reacted to nickel were more likely to be female. Those who reacted to chromate were more likely to be male and to have an occupational cause for their dermatitis. There was a strong trend for patients who reacted to cobalt to be non-Caucasian. All those who reacted to metal had increased odds of a history of atopic eczema. Chromate reactions and isolated cobalt reactions were less likely to have known relevance than other (nonmetal) allergens. Several metal allergy combinations showed a predilection toward specific dermatitis sites, especially the scalp, eyelids, ears, and lips.
Limitations: The study was a retrospective analysis, exploratory in nature, and had relatively small numbers of patients with particular multiple metal allergy combinations.
Conclusion: This research confirms the sex predilections toward nickel and chromate allergy and suggests enhanced sensitivity to metals among those with atopic eczema. The results also serve to raise questions regarding occupationally related chromate allergy in men, the relevance of cobalt allergy, exposure patterns resulting in enhanced sensitivity to cobalt in non-Caucasians, and associations between metal allergens and dermatitis site. The answers to these questions require more detailed studies.