Cobalt spot test used for diagnosis of occupationally-related exposure to cobalt-containing powder.

A cobalt spot test was recently developed (1). Testing for cobalt release is performed by dipping a white cotton stick into a clear yellow cobalt test solution containing nitroso R salt, followed by rubbing of the cotton stick for 20–30 seconds against the test item. A colour change from yellow to red–orange indicates a positive test reaction. The spot test detects approximately 8 ppm cobalt in a solution (1, 2). The cobalt spot test has proven to be useful for screening purposes, and we have shown that surprisingly few jewellery items, hair clasps, mobile phones and work tools release cobalt in significant amounts (3–5). We have also used the cobalt test in the diagnostic work-up of patients with allergic cobalt dermatitis, but have only identified cobalt release in very few cases (6). Here, we report a novel use of the cobalt spot test in a patient with allergic cobalt dermatitis in whom exposure resulted from a powdered product.