Lyme Disease Without a Rash: How Often Is an EM Rash Missing?

Many Lyme patients never recall a rash
EM rash rates depend heavily on study design
Overreliance on rash patterns may delay diagnosis

Lyme disease without rash is more common than many patients realize. People often expect a bullseye rash, yet studies have reported widely different rates of erythema migrans depending on how patients were selected.

Patients frequently ask whether Lyme disease can occur without a rash or whether the absence of a bullseye lesion makes Lyme disease unlikely. The answer is more complicated than many realize.

See also: Lyme Rash Misdiagnosis and Bullseye Rash Problems

Two studies often cited to support high erythema migrans rates may unintentionally overestimate how commonly patients develop a rash because of how participants were selected.

Both studies, published in 1996 and 1998, required participants to meet the Centers for Disease Control and Prevention (CDC) surveillance case definition for Lyme disease. That surveillance definition required erythema migrans lesions measuring at least 2 inches in diameter.

Can You Have Lyme Disease Without a Rash?

Yes. Lyme disease without a rash is well documented.

Many patients diagnosed with Lyme disease never recall seeing an erythema migrans rash. Some patients may have a rash in difficult-to-see locations, while others may never develop one that is recognized.

Overreliance on the presence of an EM rash may delay diagnosis in patients whose symptoms appear before a rash is identified—or in patients who never develop one.

What Percentage of Lyme Disease Cases Have No Rash?

The percentage varies significantly depending on study design.

When studies select patients using surveillance definitions that require erythema migrans, reported rash rates naturally rise.

Studies using broader patient populations often report substantially lower rash rates.

For example, only 25% of patients had an EM rash in the original study describing Lyme disease in Lyme, Connecticut. [4]

In a National Institutes of Health-sponsored study evaluating Lyme encephalopathy, only 56% of patients reported an erythema migrans rash despite confirmed Lyme disease based on positive IgG Western blot testing. [5]

Why EM Rash Rates May Be Inflated

Selection bias may influence reported erythema migrans rates.

If researchers require erythema migrans as part of entry criteria, studies may overestimate how often the rash occurs in real-world practice.

This distinction matters because clinicians and patients may incorrectly assume Lyme disease becomes unlikely when a rash is absent.

See also: Why Lyme Tests Medicine

Why Missing the Rash Matters

A Lyme disease patient may be denied treatment if clinicians rely too heavily on the expectation of an EM rash.

Likewise, Lyme incidence may be underestimated if public health systems overemphasize rash recognition.

Patients presenting with neurologic symptoms, fatigue, joint pain, cognitive symptoms, or other manifestations may require evaluation even when no rash is remembered.

See also: Delayed Lyme Disease Diagnosis

What Is an EM Rash?

An erythema migrans rash is the characteristic expanding skin lesion associated with Lyme disease.

Although often described as a bullseye rash, many EM lesions do not have classic central clearing.

Some lesions may appear uniformly red, oval, faint, or atypical.

See also: Lyme Disease Symptoms Guide

Frequently Asked Questions

Can you have Lyme disease without a rash?

Yes. Many Lyme disease patients never recall an erythema migrans rash.

What percentage of Lyme disease cases have no rash?

Reported rates vary widely depending on study design and patient selection methods.

What is an EM rash?

An EM rash is an expanding skin lesion associated with Lyme disease, though it may not always appear as a bullseye.

Can Lyme disease occur without a bullseye rash?

Yes. Many patients with Lyme disease either never develop a classic bullseye lesion or do not recognize one.

Clinical Takeaway

Absence of an erythema migrans rash should not automatically lower suspicion for Lyme disease.

Overreliance on rash recognition may contribute to delayed diagnosis, missed treatment opportunities, and underrecognition of Lyme disease presentations without classic skin findings.

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References

1. Shapiro ED, Wormser GP. Controversies About Lyme Disease—Reply. JAMA. 2018;320(23):2482-2483.
2. Gerber MA, Shapiro ED, Burke GS, Parcells VJ, Bell GL. Lyme disease in children in southeastern Connecticut. N Engl J Med. 1996;335(17):1270-1274.
3. Sigal LH, Zahradnik JM, Lavin P, et al. A vaccine consisting of recombinant Borrelia burgdorferi outer-surface protein A to prevent Lyme disease. N Engl J Med. 1998;339(4):216-222.
4. Steere AC, Malawista SE, Snydman DR, et al. Lyme arthritis: an epidemic of oligoarticular arthritis in children and adults in three Connecticut communities. Arthritis Rheum. 1977;20(1):7-17.
5. Fallon BA, Keilp JG, Corbera KM, et al. A randomized, placebo-controlled trial of repeated IV antibiotic therapy for Lyme encephalopathy. Neurology. 2008;70(13):992-1003.

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Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.

Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention