Erythema Multiforme

by William L. Weston, M.D.
Professor of Dermatology
University of Colorado Health Sciences Center

What is Erythema Multiforme?

Erythema Multiforme is an uncommon, self-limited symmetrical skin rash with target
lesions that begins abruptly and heals in 7 to 14 days.


What causes Erythema Multiforme?

For most people, a herpes simplex virus infection causes Erythema Multiforme, such
as an infection of the lip (i.e., a cold sore). Occasionally, Erythema Multiforme
is caused by a herpes simplex virus infection of the genitals. Rarely, other viruses
will cause it.


Who gets Erythema Multiforme?

Erythema Multiforme most commonly occurs in adolescents and, sometimes, in school
age children.


How does the herpes simplex virus cause disease?

After growing at the site of a cold sore, the herpes simplex virus will travel through
the bloodstream to the skin and then grow in the skin cells. The target lesions
associated with Erythema Multiforme are the body’s attempt to eliminate the virus.
People who are especially susceptible to the herpes simplex virus have difficulty
clearing it from their skin.


What are the common findings?

The target lesion on the skin is the most common manifestation of Erythema Multiforme.
Each target lesion has at least two zones of color change that resemble an archery
target. The center of the target lesion always has some skin damage, such as a scab
or a blister.

A herpes simplex virus infection on the lip (i.e., a cold sore) often precedes the
appearance of the target lesion(s) by one to seven days. Sometimes, though, the
preceding herpes simplex virus infection does not cause cold sores, and it is called
a “subclinical infection.” Erythema Multiforme recurs in most people, but not necessarily
after each cold sore.


How is Erythema Multiforme diagnosed?

Most physicians diagnose Erythema Multiforme from the target lesions on the skin.
However, Erythema Multiforme is frequently overdiagnosed, as large hives are often
confused for it. Large hives have normal skin in the center; Erythema Multiforme
has damaged skin in the center. Large hives often are accompanied by swelling of
the hands and feet; but, Erythema Multiforme is not accompanied by such swelling.
Large hives will clear up with antihistamines; but, Erythema Multiforme will not
clear up with such treatment.


How is Erythema Multiforme treated?

There is not an effective treatment at the time of the attack of Erythema Multiforme.
If individuals experience an attack of Erythema Multiforme every three months or
less, a preventative treatment with an oral antiherpes virus agent, such as Zovirax,
Valvir, or Famvir, is effective.


What are the complications?

If untreated, the target lesions on the skin will heal within two weeks. Steroid
treatments may prolong an attack of Erythema Multiforme. Healing usually occurs
without scarring of the skin.


How can Erythema Multiforme be prevented?

Prevention of those factors that precipitate cold sores can be helpful. For example,
sunscreen use is beneficial because sun exposure may activate the herpes simplex
virus that causes Erythema Multiforme.


What research is being done?

Studies are currently being conducted to examine how the body eliminates the herpes
simplex virus. These studies will aid in understanding why individuals who are susceptible
to the herpes simplex virus cannot effectively eliminate it despite immune responses
that are normal.


About the Author

Dr. Weston is a Professor of Pediatrics and Dermatology at the University of Colorado
Health Sciences Center and Chair of the Department of Dermatology. His scientific
and clinical interests include Cutaneous immunology, Cutaneous virology, and Pediatric

Dr. Weston is the primary author of the Color Textbook of Pediatric Dermatology
(Weston, Lane, Morelli; Mosby, Inc.) which is used by clinicians worldwide and is
published in 4 languages.

He created the Genetic Skin Disorders clinic at the University of Colorado in 1998.

Copyright 2012 William L. Weston, M.D., All Rights Reserved