Drug Eruptions: Allergic Reactions?

Abstract

Drugs often cause adverse reactions, many of which involve the skin. Life-threatening skin reactions such as toxic epidermal necrolysis are rare, just like anaphylactic shock. Less severe but still worrisome eruptions are abundant but may develop into serious reactions. Only a part (20%) of these eruptions are evoked by an allergic mechanism. Usually one does not know if the drug or a metabolite is the antigen. As a consequence, tests in vitro and in vivo will be rather unreliable. Negative tests are not helpful and not decisive as the test could be false negative. It might be necessary to carry out a provocation test, the gold standard. A provocation test is not without dangers and does not discriminate between allergic and nonallergic reactions. More clinically reliable skin and laboratory tests should be developed to identify allergic reactions and to detect the allergenicity of new drugs.