Photo Rounds

Rash on hands

A 28-year-old woman sought care for a cold sore that had been on her lip for 5 days and a rash that had been on both hands for 3 days. The patient indicated that she’d had cold sores on and off since her teen years, but had never had a rash like this before. The rash was mildly itchy, but the cold sore was painful. She was worried that the herpes had spread to her hands.

What's your diagnosis?


The family physician diagnosed erythema multiforme (EM) on the hands, secondary to an outbreak of oral herpes, in this patient. The EM on the dorsum of the hand had target lesions with small, eroded centers. (Sometimes urticaria will have target-like lesions, but there will be no epidermal erosions.)

EM is considered a hypersensitivity reaction and is often secondary to infections or medications. Herpes simplex viruses (HSVI and HSV2) are the most common causative agents and have been implicated in at least 60% of cases. EM most commonly occurs between the ages of 10 and 30 years.

There are no consistent laboratory findings with EM. The diagnosis is usually made based on clinical findings. The treatment is mainly supportive. Symptomatic relief may be provided with topical emollients, systemic antihistamines, and acetaminophen. These do not, however, alter the course of the illness. Recurrent outbreaks have been reported, and are thought to be associated with HSV infection.

If this patient were to get EM again with her HSV1, it would be reasonable to offer prophylactic acyclovir to prevent the HSV1 and the EM. Acyclovir has been used to control recurrent HSV-associated EM with some success.

Photo courtesy of the University of Texas Health Science Center at San Antonio, Division of Dermatology. This case was adapted from: Milana, C. Smith M. Hypersensitivity syndromes. In: Usatine R, Smith M, Mayeaux EJ, et al., eds. The Color Atlas of Family Medicine. New York, NY: McGraw-Hill; 2009:750-755.

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