Nickel allergy, Kounis syndrome and intracardiac metal devices.

Metal-induced allergic reactions are not rare in every day practice but nickel, cobalt and chromium are the most common offenders. Other metal anions and metal alloys represent also emerging causes for hypersensitivity reaction in humans. The metal struts of endovascular and intracardiac devices are usually alloys containing nickel and constitute causes for allergic reactions with possible intracardiac and intracoronary mast cell activation resulting in the Kounis hypersensitivity coronary syndrome. Newer intracoronary stents avoid nickel thus making them less allergenic. It is advisable that, before any device implantation, careful history of any metal allergy should be taken and efforts should be made for the development of new devices with better biocompatibility.