Herxheimer's reaction

[hûrkshī′mərz, hĕrks-]
n.
  1. An inflammatory reaction in tissues infected by spirochetes, as in syphilis or Lyme's disease, induced in certain cases by treatment with salvarsan, mercury, or antibiotics. Jarisch-Herxheimer reaction
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.