Hypersensitivity to mercuric fluorescein compounds.

The mercurial compounds are known to be a common cause of allergic contact dermatitis. Immediate hypersensitivity is rarely induced by mercurial organic derivatives. However, none of the published cases showed both immediate and delayed hypersensitivity as was the case of one of our two patients. A boy and a woman experienced urticaria and anaphylaxis, respectively after topical application of Merchromine (Merbromine). We were able to demonstrate immediate hypersensitivity in both patients to mercuric fluorescein compounds by skin test and histamine liberation. In addition, the child but not the woman, showed delayed hypersensitivity to mercurial compounds.