Jarisch-Herxheimer reaction
noun
Ja·risch-Herx·hei·mer reaction
| \ ˈyä-rish-ˈherks-ˌhī-mər-
\
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Medical Definition of Jarisch-Herxheimer reaction
: an increase in the symptoms of a spirochetal disease (as syphilis, Lyme disease, or relapsing fever) occurring in some persons when treatment with spirocheticidal drugs is started
— called also Herxheimer reaction