Gold: an allergen of growing significance.

Gold moved into the limelight of medical literature thanks to the anti-inflammatory activity and effectiveness of gold compounds in the treatment of rheumatoid arthritis, but more recently also because of the growing incidence of hypersensitivity induced by it which is expressed in cutaneous and mucosal reactions. This review discusses dermatotoxicity associated with gold. In some countries gold has moved into second place as allergen, following nickel. Such recognition is mainly due to improved diagnostic methods and to its inclusion in routine dermal patch testing. Some unconventional manifestations of hypersensitivity are associated with use patterns which involve intimate contact with the metal as a component of jewelry. In-depth analysis of the growing number of cases of allergy has revealed various immunological idiosyncrasies as being characteristic of this metal. These include late reactions to challenge, extraordinary persistence of clinical effects, formation of intracutaneous nodules and immunogenic granuloma unresponsive to conventional steroid therapy, the occurrence of eczema at sites distant from the site of contact, and flare-ups of eczema upon systemic provocation with allergen which are characteristic of drug induced allergy. These manifestations demand investigations at the molecular level of the unusual mechanisms of action involved.