I wasn't sure what a HERX reaction was so i looked it up.

I'll post what I found in case others weren't sure about what it is.

[Herxheimer reaction
From Wikipedia, the free encyclopedia

The Herxheimer reaction (also known as Jarisch-Herxheimer or Herx) occurs when large quantities of toxins are released into the body as bacteria (typically Spirochetal bacteria) die, due to antibiotic treatment or rapid detoxification.

Typically the death of these bacteria and the associated release of endotoxins occurs faster than the body can remove the toxins via the natural detoxification process performed by the kidneys and liver. It is manifested by fever, chills, headache, myalgia (muscle pain), and exacerbation of skin lesions. Duration in syphilis is normally only a few hours but can be much longer, up to months or years, for other diseases. The intensity of the reaction reflects the intensity of inflammation present.

The Herxheimer reaction has shown an increase in inflammatory cytokines during the period of exacerbation, including tumor necrosis factor alpha, interleukin-6 and interleukin-8]
http://en.wikipedia.org/wiki/Herxheimer_reaction