A case of prurigo pigmentosa considered to be contact allergy to chromium in an acupuncture needle.

A 53-year-old male developed prurigo pigmentosa on his back, after undergoing acupuncture for 3 years. The eruptions were ceased on discontinuing the therapy but recurred with its resumption. The acupuncture needle contained 18.12% chromium. Erythema was induced by patch testing with potassium dichromate, and a flare-up was observed in the area of the patch test on resumption of acupuncture. We consider that the eruptions were induced by contact allergy to the chromium component of the acupuncture needles.