<Tr> <Th> MeSH </Th> <Td> D015787 </Td> </Tr> <Tr> <Td_colspan="2"> (edit on Wikidata) </Td> </Tr> <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 cannot rule out Lyme disease, and a doctor visit is advisable . </P> <P> "Not all erythema migrans lesions are Lyme disease": A similar condition called Southern Tick Associated Rash Illness (STARI) produces a similar rash pattern although it develops more quickly and is smaller . The associated infectious agent has not been determined . Antibiotic treatment resolves the illness quickly . </P>

Erythema migrans a bullseye rash at the portal of entry is associated with