This article is from the Lyme Disease
FAQ, by Milo7
A Jarisch-Herxheimer reaction (J-H reaction) is an exacerbation of a
patient's Lyme disease symptoms shortly after the introduction of an
antibiotic. The antibiotic kills off or "lyses" the bacteria and when it
does, bacteria release toxins into the patient's system. This reaction is
similar to that seen during treatment of the spirochetal illness, syphilis.
Once antibiotics are introduced, a patient with a J-H reaction will
actually feel worse before feeling better.
Information on the Jarisch-Herxheimer reaction (commonly referred to by LD
patients as a "Herx" or "Herxheimer") can be found at:
Jarisch-Herxheimer Reaction and Lyme Disease - Links