Codeine allergy can be true allergy (caused by immunoglobulin e
that reacts with the Codeine molecule) or because Codeine can directly cause allergic mediator release from mast cells and basophils by a non-immunoglobulin e mechanism. One can use Codeine as a positive control rather than histamine
for skin testing.
One can be desensitized to a number of drugs but Codeine is not commonly attempted.