Erythema multiforme

Definition

Erythema multiforme (EM) is an acute skin reaction that comes from an infection or another trigger. EM is a self-limiting disease. This means it usually resolves on its own without treatment.

Alternative Names

EM; Erythema multiforme minor; Erythema multiforme major; Erythema multiforme minor - erythema multiforme von Hebra; Acute bullous disorder - erythema multiforme; Herpes simplex - erythema multiforme

Causes

EM is a type of allergic reaction. In most cases, it occurs in response to an infection. In rare cases, it is caused by certain medicines or body-wide (systemic) illness.

Infections that may lead to EM include:

Viruses, such as herpes simplex that cause cold sores and genital herpes (most common)
Bacteria, such as Mycoplasma pneumoniaethat cause lung infection
Fungi, such as Histoplasma capsulatum, that cause histoplasmosis

Medicines that may cause EM include:

NSAIDs
Allopurinol (treats gout)
Certain antibiotics, such as sulfonamides and aminopenicillins
Anti-seizure medicines

Systemic illnesses that are associated with EM include:

Inflammatory bowel disease, such as Crohn disease
Systemic lupus erythematosus

EM occurs mostly in adults 20 to 40 years old. People with EM may have family members who have had EM as well.

Symptoms

Symptoms of EM include:

Low-grade fever
Headache
Sore throat
Cough
Runny nose
General ill feeling
Itchy skin
Joint aches
Many skin lesions (sores or abnormal areas)

Skin sores may:

Start quickly
Come back
Spread
Be raised or discolored
Look like hives
Have a central sore surrounded by pale red rings, also called a target, iris, or bulls-eye
Have liquid-filled bumps or blisters of various sizes
Be located on the upper body, legs, arms, palms, hands, or feet
Include the face or lips
Appear evenly on both sides of the body (symmetrical)

Other symptoms may include:

There are two forms of EM:

EM minor usually involves the skin and sometimes mouth sores.
EM major often starts with a fever and joint aches. Besides the skin sores and mouth sores, there may be sores in the eyes, genitals, lung airways, or gut.

Exams and Tests

Your health care provider will look at your skin to diagnose EM. You'll be asked about your medical history, such as recent infections or medicines you've taken.

Tests may include:

Skin lesion biopsy
Examination of skin tissue under a microscope

Treatment

EM usually goes away on its own with or without treatment.

Your provider will have you stop taking any medicines that may be causing the problem. But, don't stop taking medicines on your own without talking to your provider first.

Treatment may include:

Medicines, such as antihistamines, to control itching
Moist compresses applied to the skin
Pain medicines to reduce fever and discomfort
Mouthwashes to ease discomfort of mouth sores that interferes with eating and drinking
Antibiotics for skin infections
Corticosteroids to control inflammation
Medicines for eye symptoms

Good hygiene may help prevent secondary infections (infections that occur from treating the first infection).

Use of sunscreen, protective clothing, and avoiding excessive exposure to sun may prevent the recurrence of EM.

Outlook (Prognosis)

Mild forms of EM usually get better in 2 to 6 weeks, but the problem may return.

Possible Complications

Complications of EM may include:

Patchy skin color
Return of EM, especially with HSV infection

When to Contact a Medical Professional

Contact your provider right away if you have symptoms of EM.

References

Duvic M. Urticaria, drug hypersensitivity rashes, nodules and tumors, and atrophic diseases. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 411.

Holland KE. Acquired rashes in the older child. In: Kleigman RM, Toth H, Bordini BJ, Basel D, eds. Nelson Pediatric Symptom-Based Diagnosis. 2nd ed. Philadelphia, PA: Elsevier; 2023:chap 61.

Lalor L, Shah KN. Urticaria and erythema multiforme. In: Long SS, ed. Principles and Practice of Pediatric Infectious Diseases. 6th ed. Philadelphia, PA: Elsevier; 2023:chap 71.

Rubenstein JB, Spektor T. Conjunctivitis: infectious and noninfectious. In: Yanoff M, Duker JS, eds. Ophthalmology. 5th ed. Philadelphia, PA: Elsevier; 2019:chap 4.6.