What is The Difference Between Erythema Multiforme and Migrans?

March 8, 2024

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Erythema multiforme (EM) and erythema migrans (EM) may sound similar as skin conditions associated with reddish rashes. However, recognizing the distinct differences between these two entities is key for appropriate diagnosis and management. While EM comprises inflammatory skin lesions with multiple potential triggers, EM specifically manifests in early Lyme disease transmitted by tick bites.

Understanding Erythema Multiforme

Definition and Causes

Erythema multiforme refers to a hypersensitivity reaction causing red, ring-shaped skin lesions (target lesions) most commonly triggered by herpes simplex virus (HSV) infection. Certain medications, other infections, and autoimmune disorders can also provoke EM through intricate immune pathways that remain incompletely understood.

Characteristic Signs and Symptoms

Typical target lesions start as reddish papules transforming into plaques with colored zones – dark red centers surrounded by pale rings with outer reddish halos. The symmetrical rash favors the extremities, especially the backs of hands and tops of feet but occasionally affects mucous membranes. Burning, pain and itching accompany the eruption waxed and waned over days to weeks during recurrent episodes.

Types of Erythema Multiforme

EM minor denotes limited skin findings without mucosal lesions or systemic symptoms. When severe, extensive cutaneous involvement plus oral, genital or ocular mucosa lesions occur, the term EM major applies. This resembles closely related conditions like Stevens-Johnson syndrome signaled by epithelial detachment and blisters.


Understanding Erythema Migrans

Hallmark of Lyme Disease

“An expanding circular red rash with central clearing known as a bullseye lesion on the skin serves as the hallmark for early Lyme disease diagnosis,” notes Dr. Amanda Le, infectious disease specialist. Accurate identification allows timely antibiotic therapy to treat the underlying Borrelia burgdorferi infection and prevent late complications.

Appearance and Progression

Classically manifesting at the site of the tick bite that transmitted Lyme bacteria initially, erythema migrans rash expands to form red plaques or rings over several days to weeks, often exceeding 10 cm across. The central clearing gives the signature bullseye morphology signaling borrelia spread through skin and deeper tissues to disseminate systemically if untreated.

Transmission and Symptoms

Lyme disease stems from bites of infected blacklegged ticks carrying Borrelia burgdorferi bacteria. Flu-like symptoms including fever, chills, headache and fatigue accompany the pathognomonic EM rash signaling localized then hematogenous spread. Later untreated stages cause arthritis, neurological and cardiac complications.

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Key Distinguishing Features


While EM arises from various infections or drug reactions through intricate immune cascades, EM specifically indicates early Lyme disease from Borrelia transmission by vector tick bites.


Symmetrical targetoid EM skin lesions differ from the singular, progressively expanding EM erythematous ring with central clearing reflecting localized borrelia proliferation and dissemination.


EM favors the hands, feet and occasionally mucous membranes whereas solitary EM originates at the site of a tick bite like the groin, thigh or armpits before generalized spread over the ensuing days to week.

Diagnosis and Treatment

Importance of Early and Accurate Diagnosis

Given the very different trajectories – EM being typically self-limited versus EM signifying disseminating Lyme disease, seeking prompt medical attention to correctly diagnose these superficially similar appearing rashes proves pivotal for ideal therapeutic outcomes.

Diagnostic Tests

While clinical examination provides vital clues, skin biopsy in EM and blood tests like Lyme antibody titers for EM help secure the right diagnosis to inform management.

Treatment Options

Since triggers like HSV provoke otherwise self-resolving EM, symptomatic relief suffices with close monitoring for complications in most patients. However EM indicates specific need for prompt oral antibiotics like doxycycline to eradicate Lyme infection before tissue infiltration and injury occurs.

FAQs on Erythema Multiforme and Migrans

Can I have both erythema multiforme and erythema migrans at the same time?

Concurrent diagnoses are exceptionally rare but theoretically possible if HSV reactivation and tick-borne Lyme transmission coincided to generate both pathologies simultaneously. Careful evaluation would distinguish these separate entities.

What should I do if I notice a rash that might be erythema migrans?

Urgently consult a physician when observing an expanding large ring-like rash as this likely represents Lyme disease warranting timely investigation and antibiotic therapy. Documenting appearance helps accurate diagnosis.

How long does erythema multiforme typically last?

Most cases of EM resolve within 6 weeks. Recurrent flares occur in some patients depending on the underlying trigger like HSV reactivation. Preventative antiviral medication helps when EM becomes very frequent.

Are there any home remedies that can help with erythema multiforme?

Soothing topical creams, wet wraps and oatmeal baths alleviate skin irritation and itchiness. Over-the-counter systemic antihistamines also provide symptomatic relief in EM. Strictly adhere to prescribed treatment plans.

How can I prevent Lyme disease and erythema migrans?

Protecting against tick bites using insect repellants, performing thorough skin checks after outdoor exposure, and promptly removing attached ticks help disrupt the Lyme transmission cycle to prevent infection.


  • Erythema multiforme causes inflammatory targetoid skin lesions from various triggers unlike erythema migrans which signals early Lyme disease specifically.
  • Careful history and exam combined with selected diagnostic testing accurately distinguishes between these superficially similar rashes.
  • Management drastically differs – self-care for typically self-limited EM versus antibiotics for EM Lyme infection.
  • Promoting awareness facilitates early recognition to establish correct diagnosis for ideal treatment outcomes. Ongoing research furthers evolving insights.

Consulting a doctor promptly when noticing concerning new skin findings allows systematic evaluation essential for determining appropriate therapy in these often confused conditions.

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