Electron microscopy of epidermal and dermal Langerhans' cells in long-lasting allergy patch tests

GOLD: human exposure and update on toxic risks

Gold is ubiquitous in the human environment and most people are in contact with it through wearing jewelry, dental devices, implants or therapies for rheumatoid arthritis. Gold is not a nutrient but people are exposed to it as a food colorant and in food chains. The present review discusses the hazards faced in personal and domestic use of gold and the far greater risks presented through occupational exposure to the metal in mining and processing gold ores. In the last situation, regular manual contact or inhalation of toxic or carcinogenic materials like mercury or arsenic, respectively, presents far greater hazard and greatly complicates the evaluation of gold toxicity. The uses and risks presented by new technology and use of nanoparticulate gold in anti-cancer therapies and diagnostic medicine forms a major consideration in gold toxicity, where tissue uptake and distribution are determined largely by particle size and surface characteristics. Many human problems arise through the ability of metallic gold to induce allergic contact hypersensitivity. While gold in jewelry can evoke allergic reactions, other metals such as nickel, chromium and copper present in white gold or alloys exhibit more serious clinical problems. It is concluded that toxic risks associated with gold are low in relation to the vast range of potential routes of exposure to the metal in everyday life.

Long-lasting allergic patch test reaction caused by gold

Allergic contact dermatitis caused by gold is rare, and only isolated cases have been reported. Patch testing with gold may cause a long-lasting reaction. The purpose of this study is to describe a well-studied case of gold allergy caused by dental gold crowns. A gold-sensitized patient and a non-sensitized control subject were examined using patch tests, immunohistochemistry, electron microscopy and blast transformation reactions. Sodium thiosulfate, auranofin and sodium thiomalate gave positive patch test reactions. Immunohistochemistry and electron microscopy were performed from biopsies taken from allergic patch test reactions caused by gold sodium thiosulfate 1 day and 17 days after applying the patches, from normal skin and from a 17-day-old allergic patch test reaction caused by ammonium persulfate. Down-regulation had taken place by 17 days in the allergic ammonium persulfate reaction, but not in the 17-day allergic gold test reaction. The patient reacted to all but one of the gold-induced blast transformation tests, sodium chloroaurate being non-inductive. The non-sensitized control subject did not exhibit any reactions. In conclusion, gold sodium thiosulfate, gold sodium thiomalate and auranofin can be used as patch test substances for gold allergy, though long-lasting allergic patch test reactions may develop. In vitro gold salt induced blast transformation is an alternative test for gold allergy. The slow down-regulation of the allergic patch test reactions needs to be studied further.