erythema migrans
noun
erythema mi·grans -ˈmī-grənz 
variants or erythema chronicum migrans
-ˌkrä-nə-kəm-
: a red spreading annular skin lesion that is an early symptom of Lyme disease and that develops at the site of the bite of a tick (such as the deer tick) infected with the causative spirochete
Example Sentences
Recent Examples on the Web In 70-80% of cases, the CDC also reports that people will experience an erythema migrans (EM) rash—a rash that typically in a bulls-eye shape, feels warm to the touch, and gradually expands over the course of a few days. 
Maggie O'neill, Health.com, 8 Sep. 2020 That’s especially true if patients don’t have the bullseye rash— known medically as erythema migrans—characteristic of Lyme disease. Carrie Arnold, Popular Science, 28 June 2020 Typical symptoms include fever, headache, fatigue, and a characteristic skin rash called erythema migrans. Rosy Cordero, EW.com, 8 Jan. 2020 Then, an ecologist doing field studies saved the tick that bit him where an erythema migrans formed. Allen Steere, BostonGlobe.com, 22 Aug. 2019 Early in the infection people may experience fever, headache, fatigue, swollen glands or a skin rash called erythema migrans, or a bull’s eye. Andrea K. Mcdaniels, baltimoresun.com, 3 July 2018 The most notable early symptom is a (non-itchy) rash that resembles a bull's-eye (erythema migrans) and can expand to as large as 12 inches in diameter over the course of several days. Emma Sarran Webster, Allure, 3 May 2018 See More
Maggie O'neill, Health.com, 8 Sep. 2020 That’s especially true if patients don’t have the bullseye rash— known medically as erythema migrans—characteristic of Lyme disease. Carrie Arnold, Popular Science, 28 June 2020 Typical symptoms include fever, headache, fatigue, and a characteristic skin rash called erythema migrans. Rosy Cordero, EW.com, 8 Jan. 2020 Then, an ecologist doing field studies saved the tick that bit him where an erythema migrans formed. Allen Steere, BostonGlobe.com, 22 Aug. 2019 Early in the infection people may experience fever, headache, fatigue, swollen glands or a skin rash called erythema migrans, or a bull’s eye. Andrea K. Mcdaniels, baltimoresun.com, 3 July 2018 The most notable early symptom is a (non-itchy) rash that resembles a bull's-eye (erythema migrans) and can expand to as large as 12 inches in diameter over the course of several days. Emma Sarran Webster, Allure, 3 May 2018 See More Word History
Etymology
New Latin, literally, (chronic) migrating erythema
First Known Use
1979, in the meaning defined above
Medical Definition
erythema migrans
noun
: a spreading annular erythematous skin lesion that is an early symptom of Lyme disease and that develops at the site of the bite of a tick (as the deer tick) infected with the causative spirochete
called also erythema chronicum migrans