Early recognition and management of drug related cutaneous reactions are important to prevent serious sequelae of drug hypersensitivity. Morbilliform Rash Morbilliform rash is the most common cutaneous drug eruption, and is characterized by a measles-like viral exanthem. Morbilliform reactions usually start in dependent areas and then become generalized. They usually begin 2 to 10 days after initiation of the drug, but can occur up to 14 days after a drug is stopped. The immunologic mechanism involved in this type of rash is not known.
Morbilliform rash is frequently related to antimicrobial therapy.
Sometimes a fever, leukemoid reaction, interstitial nephritis, or elevation of serum transaminase indicative of hepatocellular inflammation may accompany this type of rash. Treatment includes discontinuation of the suspected agent, topical or systemic antipruritic therapy, and a two week course of systemic corticosteroid therapy if the reaction is severe. Most morbilliform rashes resolve with some degree of superficial skin desquamation. Urticaria Urticaria, which may be associated with angioedema, can occur as a result of drug therapy and will present as evanescent, raised, red, pruritic, well demarcated lesions which disappear without residual scarring or hyperpigmentation. Urticaria due to type III reactions may be accompanied by serum sickness including fever, arthritis, nephritis, and lymphadenopathy.