Background: Keys are an important exposure source of metal allergens to consumers and confer a significant problem for nickel-allergic individuals because of repeated daily use.
Objectives: The aims of this study were to investigate the frequency of nickel and cobalt release in keys and to consider the effectiveness of coatings for preventing metallic allergen release from common metal allergen-releasing keys.
Methods: Keys from a variety of common stores were nickel and cobalt spot tested. Nickel-releasing keys were coated with enamel sprays, subjected to a use test, and retested to assess for metal allergen release.
Results: Of 55 tested keys, 80% showed a strong positive result to the nickel spot test. None of the tested keys exhibited cobalt release. No keys initially released nickel after enamel coatings. Key coatings chipped at the portion inserted into a lock after 30 insertions, and keys were found to release nickel. The handle of the key was not found to release nickel after 60 insertions.
Conclusions: Nickel release from keys is very common; nickel-allergic consumers should consider purchasing keys that do not release nickel (eg, brass, anodized). Enamel coating may be useful in protecting nickel-sensitive individuals from their keys but cannot consistently prevent nickel-release from portions used frequently.