Erythema multiforme

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 pneumoniae that cause lung infection 
• Funguses, 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 drugs 

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 often have family members who have had EM as well.

Symptoms of EM include:

• Fever
• 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:

• Bloodshot eyes
• Dry eyes
• Eye burning, itching, and discharge
• Eye pain
• Mouth sores
• Vision problems

There are 2 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.

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

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 symptoms 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 and staying away from other people may help prevent secondary infections (infections that occur from treating the first infection).

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

Complications of EM may include:

• Patchy skin color
• Return of EM, especially with HSV infection

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

French LE, Prins C. Erythema multiforme, Stevens-Johnson syndrome and toxic epidermal necrolysis. In: Bolognia JL, Jorizzo JL, Schaffer JV, eds. Dermatology. 3rd ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 20.

Revuz J. Erythema multiforme. In: Lebwohl MG, Heymann WR, Berth-Jones J, Coulson I, eds. Treatment of Skin Disease: Comprehensive Therapeutic Strategies. 4th ed. Philadelphia, PA: Elsevier Saunders; 2014:chap 72.

Sokumbi O, Wetter DA. Clinical features, diagnosis, and treatment of erythema multiforme: a review for the practicing dermatologist. Int J Dermatol. 2012;51(8):889-902. PMID: 22788803 www.ncbi.nlm.nih.gov/pubmed/22788803.