Erythema Chronicum Migrans (Lyme Disease)

Lyme Disease Rash / Bull's-Eye Rash

Overview

Erythema chronicum migrans (ECM) is the characteristic skin rash of early Lyme disease, caused by the spirochete Borrelia burgdorferi transmitted through the bite of an infected Ixodes (deer) tick. The rash typically appears as an expanding red patch, often with central clearing that creates a bull's-eye or target-like pattern. It is the hallmark sign of Lyme disease and an important clinical clue for early diagnosis and treatment.

Key Symptoms

• Expanding red or pink patch at the site of a tick bite
• Classic bull's-eye or target pattern with central clearing (not always present)
• Rash typically appears 3-30 days after the tick bite
• Gradually enlarges over days to weeks, often reaching 12 inches or more
• Usually painless but may feel warm to the touch; mild itching possible
• May be accompanied by fever, fatigue, headache, and muscle or joint aches

Affected Areas

Site of tick bite (anywhere on body), Trunk, Thighs, Groin, Axillae (armpits)

Care Instructions

1. See a healthcare provider promptly if you develop an expanding rash after a tick bite.
2. Early treatment with oral antibiotics (typically doxycycline) is highly effective.
3. Complete the full course of prescribed antibiotics even if symptoms improve.
4. Check for ticks after spending time outdoors in endemic areas.
5. Use insect repellent containing DEET and wear protective clothing in wooded or grassy areas.
6. Remove attached ticks promptly with fine-tipped tweezers, grasping close to the skin.

Medical Disclaimer: This information is for educational purposes only and does not replace professional medical advice. Always consult a qualified dermatologist for diagnosis and treatment.

Prevalence: Common in endemic areas; approximately 476,000 cases of Lyme disease are diagnosed annually in the United States