Patients with erythema multiforme (EM) will complain of pain and burning, rather than itching.2 Both mucosal surfaces and skin may be involved, with typical targetoid lesions often distributed acrally.2 Overlying blistering or necrosis of the epidermis is commonly seen in EM, and like SSLR, the plaques are fixed, rather than transient. Although the plaques of UM, SSLR, and EM can all contain a dusky center, the lesions of SSLR and EM usually resolve with postinflammatory hyperpigmentation, which is typically not seen in UM.1,2
Stop the offending drug, start an antihistamine
Treatment for UM involves discontinuing the offending medication and inhibiting the effects of histamine release. The combination of second-generation antihistamines (eg, cetirizine, fexofenadine, or loratadine) every morning and first-generation antihistamines (eg, diphenhydramine) at night for pruritus is the mainstay of treatment.1,2 Acetaminophen can be used for mild fever; however, aspirin and nonsteroidal anti-inflammatory drugs should be avoided because these medications may worsen the urticarial eruption.4
Our patient had already finished her course of amoxicillin when she first presented with the rash, so we prescribed an oral antihistamine—cetirizine 5 mg BID. Six days after rash onset, when mother and child returned for follow-up, the patient’s lesions had completely resolved. There was no residual postinflammatory hyperpigmentation, which confirmed the diagnosis of UM.
We advised the mother that her daughter was allergic to amoxicillin and told her to avoid it in the future.
CORRESPONDENCE
Casey Bowen, MD, Dermatology Clinic, 2200 Bergquist Dr, STE 1, JBSA-Lackland, TX 78236-9908; casey.bowen.2@us.af.mil