A dental amalgam is alloy of silver, copper and tin with a small amount of mercury. Trace amounts of the mercury may be absorbed by the patient, but this may be enough for a patient with a contact sensitivity to mercury to develop a systemic reaction.
Clinical features:
(1) presence of one or more amalgam fillings
(2) systemic dermatitis (see below)
(3) positive patch test to mercury
(4) disappearance of the skin rash on removal of the amalgam fillings
The dermatitis may take the form of:
(1) flexural dermatitis
(2) baboon syndrome
(3) maculopapular rash
(4) nummular dermatitis
In theory, the diagnosis can be confirmed by a challenge test to amalgam, but this is only rarely done.
A similar reaction can occur in a person with gold fillings and a gold sensitivity.
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