The rash that can accompany Lyme disease called Erythema Migrans (EM) should be taken seriously by doctors. Treatment during this stage is critical to avoid long term infection & possible progression to chronic Lyme disease which is much harder to cure. Blood tests done at this early stage will prove negative until roughly 4 weeks after infection so prompt treatment is vital. The rash occurs in 50% or less of Lyme diseases cases.
But how would I know what a rash looks like?
Below are some good sites that reveal pictures of rashes. As you can see, the rash can be small, it can be large, it can be spread or contained in a bull’s eye ring, it can be brown or red, it can even develop slowly or recur sometime after the bite. It may not even be at the site of the bite or may go unnoticed under hair.
Some rash pictures can be found at:
How to Tell the Difference between ringworm & EM Rashes
*Newly added 19th Setember 2012
If you had lyme you’d see a rash – (or maybe not)
There is a familiar pattern going around the world. Patients, doctors & the public are repeatedly told that lyme will nearly always emit a bulls-eye shaped lesion days to weeks after a bite. Some studies I’ve seen suggest up to 90% of patients others as low as 50%. Another actually suggested as low as 9%* are typical bulls-eye (EM) lesions the rest are multiple EM rashes, uniform EM rashes in fact a whole manner of forms**. Rashes can appear by the bite, away from it, can repeatedly occur throughout the illness. According to a study at the Univ College Hospital they found “While twenty-two patients (71%) had a rash at presentation, only 43% of patients presented with EM rash“.
Results of our own surveys (word doc) found that the erythema migrans (EM) rash was only present in 44% of the patients at the start of the illness and 19% have multiple EM’s during the course of the illness. This shows that a rash is not always present or noticed during Stage One of the illness… Also differing strains can cause differing skin reactions so really it is hard to pin down an exact percentage. Just be known that a bulls-eye rash does not appear in everyone & those who do get a rash it may not be conforming to the normal picture portrayed. Some pics of differing rashes can be seen at: http://www.ticktalkireland.org/diagnosis.html
*[PDF]The EM lesion has been classically described as erythematous with central clearing, the so-named “bull’s eye” appearance (Figure 3) (4). However, in a study of 118 cases of EM, in which Borrelia burgdorferi infection was confirmed by culture or polymerase chain reaction, the lesion was homogeneous in 59%, had central erythema in 32% (Figure 4), and was a “bull’s eye” with central clearing in only 9%.
**In another study that contains pics of various rashes” While 80% of EM in the United States are uniformly red, only 19% have the stereotypical bull’s eye appearance .
While typically circular or oval, it can also be triangular, rectangular or distorted in other ways when occurring in areas such as the neck . Atypical features may include erythema with central induration, urticarial like lesions, confluent red-blue lesions mimicking ecchymosis, vesicles mimicking shingles, and central necrosis mimicking spider bites”
*Newly added 30th March 2012
Beware, EM rashes are not always present & DO NOT always represent the bulls-eye target lesion that is often associated with early lyme disease:
The study below is a good example of the challenges faced by the treating physician in spotting lyme disease…
Diagnostic challenges of early Lyme disease: Lessons from a community case series
BMC Infect Dis. 2009; 9: 79.
Published online 2009 June 1. doi: 10.1186/1471-2334-9-79 PMCID: PMC2698836
Copyright ©2009 Aucott et al; licensee BioMed Central Ltd.
John Aucott,corresponding author1 Candis Morrison,#2 Beatriz Munoz,#3 Peter C Rowe,#4 Alison Schwarzwalder,#2 and Sheila K West#3
EM was the most common presentation of early Lyme disease in our series. However, prior misdiagnosis remained common, confirming previous reports from other endemic areas . Patients and physicians often saw the EM but were unaware of its significance, understandable considering the substantial variation in its morphology . While 80% of EM in the United States are uniformly red, only 19% have the stereotypical bull’s eye appearance . While typically circular or oval, it can also be triangular, rectangular or distorted in other ways when occurring in areas such as the neck . Atypical features may include erythema with central induration, urticarial like lesions, confluent red-blue lesions mimicking ecchymosis, vesicles mimicking shingles, and central necrosis mimicking spider bites [6,25,26]. Examples of typical and atypical lesions are shown in Figures Figures 2,2, ,3,3, ,4,4, ,55 and and 6.6.(see link below) In our series, the most common misdiagnosis for EM was spider bite, consistent with observations that spider bites may be commonly over-diagnosed .
Figure 3 - example of multiple uniform rashes: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2698836/figure/F3/
Figure 6 – classic bulls-eye rash: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2698836/figure/F6/
The common misconception that a bull’s eye EM is the only diagnostic manifestation of Lyme disease continues to mislead both patients and practitioners. The absence of EM for 13% of our early Lyme cases highlights this discrepancy, with the majority of these seropositive patients (54%) developing only non-specific, viral-like illnesses without objective manifestations. Little attention has been afforded this presentation, despite the recognition that it may account for up to 9–16% of all early cases [15,29,30]. However, the IDSA guidelines for the management of Lyme disease do not specifically address nor provide treatment options for this subset of patients  and they are not included in treatment trials or long term outcome studies [31,32]…
..Our patients with early Lyme disease defined by extracutanous, objective neurologic or cardiac disease often had systemic presentations with abdominal pain, chest symptoms or other atypical features. This misled clinicians to treat incorrect etiologies, including diverticulitis, acute coronary syndrome, sciatica, and lymphoma. Especially confusing are systemic presentations with elevated AST and ALT, previously reported in 37% of presenting patients [33,34]. Chest or abdominal pain are uncommon but elusive presentations of Lyme disease that may be due to cardiac involvement or radiculopathy involving the thoracic dermatomes [35-37].
Among previously misdiagnosed early Lyme patients, 41% received ineffective antibiotics which have been associated with treatment failures and higher relapse rates [11,12,38]. For misdiagnosed patients or those presenting with a viral-like illness, administration of ineffective antibiotics may produce unintended consequences. In studies showing suboptimal results with azithromycin, patients were often seronegative after treatment , raising the potential impact of sub-optimal therapy on seroconversion and further complicating reliance on a serology-based diagnosis . In our series, seronegative patients presenting with a viral-like illness were significantly more likely to have been exposed to antibiotics prior to confirmatory serology than those who tested positive. The impact of ineffective antibiotics on early Lyme disease warrants further research.