Chromate-allergic patients challenged orally with potassium dichromate

30 patients who had positive patch tests to potassium dichromate participated in a placebo‐controlled oral challenge with 2.5 mg chromium given as potassium dichromate. 17 reacted to chromate but not to the placebo, 2 reacted to both chromate and the placebo, and 4 reacted to the placebo but not chromate. 7 patients had no reaction. A specific reaction to chromate was most common among patients with dermatitis of the hands and/or feet.