Cobalt release from implants and consumer items and characteristics of cobalt sensitized patients with dermatitis

Background. Cobalt allergy is prevalent in dermatitis patients. Very little documentation exists about current sources of cobalt exposure.Objectives. To investigate and discuss putative sources of cobalt exposure and to present selected epidemiological data on cobalt allergy from patch-tested dermatitis patients in an attempt to better understand cobalt allergy.Materials and methods. 19 780 dermatitis patients aged 4-99 years were patch tested with nickel, chromium or cobalt between 1985 and 2010. The cobalt spot test was used to test for cobalt ion release from mobile phones as well as cobalt-containing dental alloys and revised hip implant components.Results. Six of eight dental alloys and 10 of 98 revised hip implant components released cobalt in the cobalt spot test, whereas none of 50 mobile phones gave positive reactions. The clinical relevance of positive cobalt test reactions was difficult to determine in the majority of patients. Isolated patch test reactivity to cobalt was less associated with occupational dermatitis and hand eczema than patch test reactivity to cobalt in combination with other contact allergies.Conclusions. It is often difficult to interpret the relevance of a positive patch test reaction to cobalt, and there is a need for further studies to determine sources of cobalt exposure.