while EM typically first appears on the hands and feet before progressing centrally The treatment for drug-induced urticaria is withdrawal of the causative medication and treatment with both H1- and H2-blocking oral antihistamines for up to to weeks For cases that persist despite maximum dosing of nonsedating H1- and H2-blocking antihistamines, oral steroids may be beneficial MORBILLIFORM Morbilliform, or measles-like, describes an eruption characterized by both erythematous macules and papules ( Fig 68.3 ) The term “maculopapular” is often used to describe this eruption, but morbilliform is a more precise description This is the most common type of drug rash The eruption typically starts on the trunk before spreading to involve the extremities and face, though the mucous membranes are spared The eruption can become diffuse and confluent Pruritus may be present A morbilliform drug eruption typically appears to 14 days after medication initiation, but in a previously sensitized patient it may appear within hours to days of reexposure Antibiotics, in particular penicillins ( Fig 68.4 ), cephalosporins, sulfonamides, and antiepileptics are common triggers A morbilliform drug eruption can be difficult to clinically distinguish from a viral exanthem One unique example is that of the morbilliform eruption that may result from antibiotic administration, most commonly amoxicillin, during an Epstein–Barr virus (EBV) infection Although early studies reported an incidence of 90% or more, a more recent study suggests that the true incidence is closer to 30% This eruption, however, is not actually a drug hypersensitivity reaction (DHR), but rather is a viral exanthem Treatment involves a balance between the severity of the eruption and the importance of the causative medication The rash is generally self-limited and will resolve within to 14 days of stopping the medication However, if the rash is mild and the medication is essential, then the medication can be continued with close monitoring Morbilliform drug eruptions not progress into more severe drug reactions, however, severe drug reactions may mimic a morbilliform drug eruption early on Therefore, an uncomplicated morbilliform drug eruption must be distinguished from DHR, which has systemic involvement If the eruption appears within the first weeks of starting a medication, then it is more likely to be a morbilliform drug eruption If the eruption is delayed by several weeks, then DHR is more likely The presence of additional clinical features, such as facial edema and lymphadenopathy, and laboratory findings can also aid in distinguishing the two entities If needed, topical steroids can help provide symptomatic relief of pruritus DRUG HYPERSENSITIVITY REACTION (DHR)/DRUG REACTION WITH EOSINOPHILIA AND SYSTEMIC SYMPTOMS (DRESS) The cutaneous eruption of DHR, also known as drug reaction with eosinophilia and systemic symptoms (DRESS), is a morbilliform eruption that starts on the face and spreads cephalocaudally Additional clinical findings and systemic involvement distinguish DHR from a skin-limited morbilliform drug eruption Facial edema is present in approximately 76%, fever in 90%, and lymphadenopathy in 54% of patients with DHR In half of patients, there can be mild mucosal involvement, more commonly the oral mucosa Systemic involvement commonly manifests with eosinophilia (95%) or atypical lymphocytosis (67%) on complete blood count Liver involvement is seen in 75% of patients, and often presents as elevation of liver transaminases In cases where patients have a prolonged clinical course or when they appear systemically ill, echocardiogram, renal function tests, and coagulation profiles should be checked for cardiac, renal, and hepatic involvement Thyroid involvement is usually delayed in onset, so thyroid functions should be followed for to months after the DHR FIGURE 68.1 Widespread transient erythematous edematous papules and plaques (Reprinted with permission from Fleisher GR, Ludwig S, Baskin MN Atlas of Pediatric Emergency Medicine Philadelphia, PA: Lippincott Williams & Wilkins; 2004.) FIGURE 68.2 Urticaria often appears as annular or polycyclic plaques with central clearing or purpura (Reprinted with permission from Burkhart C, Morrell D, Goldsmith LA, et al VisualDx: Essential Pediatric Dermatology Philadelphia, PA: Lippincott Williams & Wilkins; 2009.) FIGURE 68.3 A morbilliform eruption presents with erythematous macules and papules on the trunk before spreading to the rest of the body (Courtesy of George A Datto, III, MD.) ... and plaques (Reprinted with permission from Fleisher GR, Ludwig S, Baskin MN Atlas of Pediatric Emergency Medicine Philadelphia, PA: Lippincott Williams & Wilkins; 2004.) FIGURE 68.2 Urticaria... (Reprinted with permission from Burkhart C, Morrell D, Goldsmith LA, et al VisualDx: Essential Pediatric Dermatology Philadelphia, PA: Lippincott Williams & Wilkins; 2009.) FIGURE 68.3 A morbilliform