Erythema Migrans: the misinformation continues

As we dig our way towards spring, the National Parks Traveler Website would like us to be more aware of the dangers of Lyme disease.  They’ve just released a nice article describing how AT hikers are often unable to describe the key features of Lyme disease.

Nice article, but it has a big boo boo.  NP traveler correctly points out that the majority of people who acquire Lyme initially present with a rash called erythema migrans (EM).  They go on to incorrectly describe the rash as having a bullseye characteristic and cite the somewhat misleading CDC Lyme information page.

The truth is that bullseye rashes make up a minority of EM presentations and they should not be thought of as a characteristic of EM.

The distinguishing characteristics of EM are:

– Round or oval, enlarges in size over days/weeks
– Red, sometimes warm.
– Usually greater than 2” inches in diameter, often 6-8”

Bullseye rashes, though occasionally occurring with EM, are not a characteristic of EM.  The fact that news and information websites like NP Traveler continue to perpetuate the idea that the bullseye rash is a key sign for Lyme for only worsens the problem of under and misdiagnosis.

Don’t believe me?  See what the Lyme Disease Research Foundation at John’s Hopkins University has to say.  Another good resource is an article I wrote on Lyme some years back for Backpackinglight Magazine.

Ioxedes scapularis (deer tick)

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