After a short description of the fundamental basis of allergy, particularly in relation to contact allergy, the authors review the 41 published cases of allergy to dental amalgam consisting of 30 female and 11 male patients. 20 of these patients recovered on removal of the dental amalgam. The most frequent symptoms were of the remote cutaneous type (38/41 cases) while local symptoms, particularly gingivitis and stomatitis, occurred in 17 cases. These probably underestimate the true prevalence of the condition for several reported cases have not been published. The authors then go on to describe the sensitizing property of amalgam in relation to the occupational environment and the length of time that the amalgam has been in the mouth. Mercury is the most common sensitizing agent, but other metals, particularly cooper, zinc or silver could also be implicated. The authors attempted to explain the physio-pathological mechanism of sensitization via the cutaneous as well as the oral, digestive and respiratory tracts by describing the chelating properties of metals with cellular or tissue constituents. In the last chapter, the prevention and clinical treatment of sensitization to dental amalgams is described.