Infections or medications can trigger erythema multiforme, a skin condition that causes a rash that can vary in severity and appearance. It can affect the mucous membranes of the mouth, eyes, or genitals. Usually, erythema multiforme disappears on its own within a few weeks, but it can be extremely uncomfortable and require treatment if complications arise.
The exact cause of erythema multiforme is not fully understood, but it is believed to be an immune system reaction to a foreign substance, such as an infection or a medication. Cold sores and genital herpes are commonly caused by herpes simplex virus (HSV), which triggers erythema multiforme. Cytomegalovirus (CMV), mycoplasma pneumonia, and hepatitis can also cause erythema multiforme. NSAIDs, antibiotics, anticonvulsants, and allopurinol are some medications that can trigger erythema multiforme. However, in many cases, the cause is unknown.
The main symptom of erythema multiforme is a rash that usually starts on the arms, legs, hands, and feet, and then spreads to the trunk, face, and neck. The rash can have different forms, such as:
Red, raised patches that are a few centimeters in size and may have a dark center and a pale ring around it, giving it a target-like appearance.
Small, fluid-filled blisters that may burst and crust over.
Large, red areas of skin that may peel off and expose raw, painful skin.
The rash can be mildly itchy or uncomfortable, but it is not contagious. The rash usually lasts for two to four weeks and then fades away, leaving no scars.
Depending on the severity of the condition, erythema multiforme can also affect the mucous membranes of the mouth, eyes, and genitals, causing symptoms such as:
Swollen, crusted lips and mouth sores that can make it difficult to eat and drink.
Red, sore, dry, and sensitive eyes that can affect the vision and increase the risk of infection.
Painful urination and genital sores that can interfere with sexual activity.
Some people with erythema multiforme may also have other symptoms, such as:
Fever
Headache
Fatigue
Joint and muscle pain
Sore throat
Cough
Runny nose
It is usually diagnosed based on the appearance of the rash and a history of exposure to a potentially trigger, such as an infection or medication. In order to confirm the diagnosis and rule out conditions that may cause similar symptoms, such as lupus, Stevens-Johnson syndrome, or toxic epidermal necrolysis, a skin biopsy or blood test may be performed.
The treatment of erythema multiforme depends on the severity of the condition and the symptoms. The main goals of treatment are to:
Identify and avoid the trigger, if possible.
Relieve the symptoms and prevent complications.
Support the healing of the skin and mucous membranes.
The treatment options may include:
Stopping the medication that caused the reaction, if applicable, and switching to a different one.
Taking antiviral medication, if the trigger is HSV, to reduce the duration and frequency of outbreaks.
Applying moisturizing creams, lotions, or ointments to the skin to keep it hydrated and prevent cracking and infection.
Taking over-the-counter pain relievers, such as acetaminophen or ibuprofen, to reduce the pain and inflammation.
Taking antihistamines, such as diphenhydramine or cetirizine, to reduce the itching and swelling.
Using topical steroids, such as hydrocortisone or betamethasone, to reduce the inflammation and speed up the healing of the skin.
Using oral steroids, such as prednisone or methylprednisolone, to reduce the inflammation and prevent the spread of the rash, especially if the eyes or lungs are involved.
Using antibiotics, if there is a bacterial infection of the skin or mucous membranes, to prevent further complications.
Using artificial tears, eye drops, or ointments to lubricate and protect the eyes, and wearing sunglasses to avoid sunlight exposure.
Using mouthwashes, gels, or sprays to soothe and heal the mouth sores, and avoiding spicy, acidic, or hot foods and drinks that can irritate the mouth.
Using gentle cleansers and warm water to wash the genitals, and wearing loose-fitting cotton underwear to prevent friction and irritation.
In severe cases, erythema multiforme may require hospitalization and intensive care, especially if there is extensive skin loss, dehydration, infection, or organ damage. The treatment may include:
Intravenous fluids and electrolytes to maintain hydration and prevent shock.
Intravenous antibiotics to treat or prevent systemic infection.
Intravenous immunoglobulins to modulate the immune system and reduce the severity of the reaction.
Skin grafts or biologic dressings to cover and heal the large areas of skin loss.
There is no sure way to prevent erythema multiforme, but some measures that may help reduce the risk or recurrence include:
Avoiding the medication that caused the reaction, if known, and informing the doctor and pharmacist about the allergy.
Taking antiviral medication, if the trigger is HSV, to suppress the virus and prevent outbreaks.
Practicing good hygiene and avoiding contact with people who have infections that can trigger erythema multiforme, such as HSV, CMV, or mycoplasma pneumonia.
Getting vaccinated against infections that can cause erythema multiforme, such as hepatitis B.
Using sunscreen and protective clothing to avoid sun exposure, which can worsen the rash.
Seeking medical attention as soon as possible if the symptoms of erythema multiforme appear, especially if they are severe or affect the eyes or mucous membranes.
