Erythema Multiforme ICD-10: L51.9

Immune-mediated skin reaction

Often searched as: target shaped rash on skin, ring shaped rash on hands, bullseye rash not Lyme disease, rash after cold sore, red circles on arms and legs, rash after being sick, rash from medication, weird ring rash on body…

Clinical urgency level

lowmediumhigh

Systems Affected

skinmucous membraneseyes (in severe cases)genitals (in severe cases)

Severity Levels

mild

Erythema multiforme minor — target lesions on skin only (typically hands and arms), no mucosal involvement, self-resolving in 2–4 weeks.

moderate

Erythema multiforme major — skin lesions with involvement of one mucous membrane (usually mouth), some systemic symptoms like fever.

severe

Extensive mucosal involvement across two or more sites (mouth, eyes, genitals), widespread blistering — approaches Stevens-Johnson syndrome territory and requires urgent hospitalization.

Red Flags

Blisters or sores developing inside the mouth or on the eyes
Fever above 38.5°C (101.3°F) alongside skin lesions
Rapidly spreading lesions over large areas of the body
Genital sores appearing alongside skin rash
Difficulty opening eyes, severe eye redness or discharge
Known history of herpes simplex — recurrence may trigger a new EM episode

Clinical Presentation

Erythema multiforme — classic target-shaped lesions on the forearm

Source: Wikimedia Commons (CC BY-SA 3.0 )

Erythema multiforme image gallery — DermNet NZ

View gallery on DermNet NZ (image gallery reference)

When to See a Doctor

See a doctor promptly if you develop unusual target-shaped or ring-like lesions on your skin, especially if they appear suddenly after a cold sore or after starting a new medication. Seek emergency care if mouth sores, eye involvement, or widespread blistering develop alongside the rash.

Differential Diagnosis

Stevens-Johnson Syndrome (SJS) / Toxic Epidermal Necrolysis (TEN) — severe drug reactions
Urticarial vasculitis
Fixed drug eruption
Bullous pemphigoid
Viral exanthem
Secondary syphilis
Sweet syndrome

Comorbidities

Recurrent herpes simplex virus (HSV) infection — most common trigger
Mycoplasma pneumoniae infection (especially in children)
Immunosuppression (higher risk of severe or recurrent episodes)
History of drug hypersensitivity

Prognosis

Erythema multiforme minor is self-limiting and resolves completely within 2–4 weeks without scarring. Recurrent episodes are common, especially when triggered by herpes simplex — long-term oral antiviral therapy (acyclovir) can prevent recurrence in these patients. Erythema multiforme major with significant mucosal involvement requires closer monitoring but generally has a good prognosis with appropriate treatment. It is distinct from and less severe than Stevens-Johnson Syndrome.

Detailed Overview

Causes, Symptoms, and When to Take Action Erythema multiforme is an acute, immune-mediated skin condition that develops as a reaction to certain infections or, less commonly, medications. It is characterized by distinctive target-like lesions on the skin and, in some cases, involvement of mucous membranes. How It Looks Texture: Raised, red, or swollen patches that may evolve into blisters or vesicles Color: Red, pink, or purple lesions with a central dark spot surrounded by a pale ring and an outer red area Shape: Target-shaped or iris-like lesions, often symmetrical Location: Typically appears on the arms, hands, legs, and sometimes the trunk; in severe cases, lesions may affect the mouth, eyes, or genitals Why Does It Appear? Most commonly triggered by infections, especially the herpes simplex virus Occasionally caused by certain medications The reaction occurs due to an immune response directed against the skin following the triggering event Should You Be Concerned? Erythema multiforme is usually mild and resolves within two to four weeks. However, medical attention is important if: Lesions become widespread or painful Mucous membranes (mouth, eyes, genitals) are affected You experience fever, weakness, or other systemic symptoms Can You Prevent It? Prevention depends on identifying and managing the underlying cause Controlling recurrent herpes infections and avoiding known medication triggers can help reduce recurrence Early recognition of symptoms allows timely management 👉 How Piel AI Can Help Piel AI can help track the appearance and development of lesions over time. While it is not a diagnostic tool, it supports monitoring and helps determine when to seek medical evaluation. Summary Erythema multiforme is an immune-mediated skin reaction often triggered by infection or medication. Typical signs include target-shaped lesions and, in some cases, mucosal involvement. Most cases are mild and self-resolving, but severe forms require medical care. Monitoring and early evaluation are key to effective management.

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