<P> Erythema chronicum migrans ( New Latin , literally , `` chronic migrating redness '' ) refers to the rash often ( though not always ) seen in the early stage of Lyme disease . It can appear anywhere from one day to one month after a tick bite . This rash does not represent an allergic reaction to the bite , but rather an actual skin infection of one of the Lyme bacteria species from the genus Borrelia . `` Erythema migrans is the only manifestation of Lyme disease in the United States that is sufficiently distinctive to allow clinical diagnosis in the absence of laboratory confirmation . '' It is a pathognomonic sign : a physician - identified rash warrants an instant diagnosis of Lyme disease and immediate treatment without further testing , even by the strict criteria of the Centers for Disease Control and Prevention . Such target lesions ( bull 's - eye rashes ) are characteristic of Borrelia infections , and no other pathogens are known that cause this form of rash . It is also true , though , that the rash in Lyme disease may also be solid rather than bullseye - shaped , so self - diagnosis can not rule out Lyme disease , and a doctor visit is advisable . </P>
<P> Erythema chronicum migrans ( New Latin , literally , `` chronic migrating redness '' ) refers to the rash often ( though not always ) seen in the early stage of Lyme disease . It can appear anywhere from one day to one month after a tick bite . This rash does not represent an allergic reaction to the bite , but rather an actual skin infection of one of the Lyme bacteria species from the genus Borrelia . `` Erythema migrans is the only manifestation of Lyme disease in the United States that is sufficiently distinctive to allow clinical diagnosis in the absence of laboratory confirmation . '' It is a pathognomonic sign : a physician - identified rash warrants an instant diagnosis of Lyme disease and immediate treatment without further testing , even by the strict criteria of the Centers for Disease Control and Prevention . Such target lesions ( bull 's - eye rashes ) are characteristic of Borrelia infections , and no other pathogens are known that cause this form of rash . It is also true , though , that the rash in Lyme disease may also be solid rather than bullseye - shaped , so self - diagnosis can not rule out Lyme disease , and a doctor visit is advisable . </P>
erythema migrans a bullseye rash at the portal of entry is associated with
erythema migrans a bullseye rash at the portal of entry is associated with
Lyme disease
Lyme disease