What is the definition or description of: mercury allergy?

Doesn't exist: There is no such thing as mercury allergy although a small percentage of doctors and dentists will say that mercury allergy exists. Tests that are not scientifically reliable have been used to support the idea of mercury allergy. I would not have any mercury based dental fillings removed based on unreliable and unproven allergy tests.

Not so emphatically: Contact dermatitis specialists still mention thimerosal, an antiseptic that was used in vaccines (an organic compound of mercury) and amalgam, the salt of mercury used in fillings as potential contact allergens. However, a positive reaction of both on patch testing does not mean that someone's dental filling is the cause of an oral problem. Thimerosal can also irritate skin directly.