Why Lyme Rash Misdiagnosis Happens

When most people hear “Lyme disease,” they imagine the classic bull’s-eye (erythema migrans) rash. In reality, that textbook image is the exception, not the rule. Fewer than half of patients develop the bull’s-eye pattern.

Instead, the rash may appear as a simple red patch, multiple spots across the body, or take on unusual shapes that don’t match the familiar ring. This makes it easy to overlook early signs of infection.

That’s why Lyme rash misdiagnosis is so common. Patients are often told their rash is a spider bite, ringworm, cellulitis, or eczema. These mislabels delay treatment — sometimes for months — allowing the infection to spread to joints, nerves, and the brain.

Types of Lyme Rashes

Lyme disease skin findings vary more than most clinicians realize which may lead to a misdiagnosis. While erythema migrans (EM) is the hallmark finding, Lyme disease rashes can appear in a variety of forms and patterns.

A Lyme-related rash can appear as:

1. Solid red lesions – the most common form, often mistaken for cellulitis or an allergic reaction

2. Multiple rashes – when the infection has disseminated through the bloodstream

3. Atypical or faint presentations – sometimes dismissed as heat rash, hives, or viral exanthems

Importantly, while the bull’s-eye rash is typically described as “expanding,” many Lyme rashes do not expand or change dramatically in appearance, which further contributes to misdiagnosis.

Clinical Clues That Point to Lyme

Research shows that Lyme rashes are:

1. Sometimes warm to the touch, but usually not painful like cellulitis

2. May be stable in size, rather than expanding day by day

3. Frequently larger than 2 inches in diameter by the time patients seek care

A skin biopsy may show some inflammation around blood vessels, but these findings are nonspecific and don’t provide a clear diagnosis of Lyme disease. For this reason, doctors must rely on clinical judgment to diagnose Lyme disease, rather than relying solely on the presence of a rash.

Why It Matters

Each time a Lyme disease rash is mistaken for another condition, it represents a missed opportunity for early treatment — when the chances of full recovery are highest. Patients who are reassured they don’t have Lyme may later develop fatigue, brain fog, joint swelling, or nerve symptoms — complications that might have been prevented with timely care.

Takeaways for Clinicians

1. Consider Lyme disease whenever a patient presents with an unexplained lesion, even if it isn’t expanding.

2. Don’t wait for blood tests to confirm early Lyme — treat empirically when an EM rash is suspected.

3. Educate patients on the possibility that other types of rashes, not just the bull’s-eye rash, can be a sign of Lyme disease.

Final Word

The belief that all Lyme rashes look like bull’s-eyes or that they must expand has delayed diagnosis for countless patients, costing them both time and health. Lyme rash misdiagnosis is preventable when clinicians and families recognize that skin signs can be subtle, variable, and easily mistaken for something else.

By broadening the differential and trusting clinical suspicion, we can diagnose earlier, treat faster, and prevent chronic suffering.

Resources

1. 1. 1. CDC website – Lyme Disease Rashes
      2. Dr. Cameron’s blog – Atypical findings in Lyme disease makes diagnosing difficult
      3. Dr. Cameron’s blog – Lyme disease mimics cellulitis skin infection