The Herxheimer Reaction, nicknamed "herx", otherwise referred to as Jarisch-Herxheimer is a phenomenon originally observed in the treatment of Syphilis, but later found in other illness. It is described as a temporary increase of symptoms when drugs antibiotics are administered. What is known or speculated about Lyme disease Herxheimers are based heavily on the reactions seen in syphilis. This is due to the fact both diseases are caused by a bacteria known as a spirochete. However the Herxheimer Reactions in Lyme disease are not identical to those seen in syphilis, especially in terms of timing, frequency and duration.
In Lyme disease it is thought that the cause of Herxheimers are the result of endotoxin release, that is toxins within the spirochete that are released as the Bb are killed or broken down. This may be a result of the toxins itself or the body's immune response to such.
As mentioned, the general description is a temporary increase in symptoms, but also included is the development of new ones. More specifically the most common events include: increased joint or muscle pain, headaches, chills, fever (usually low grade), drop in blood pressure, hives and rash. A multitude of other symptoms have been described.
Timing, Frequency, and Duration:
This is individualistic and
Herxheimer Reactions can occur within days to weeks after the onset of antibiotic
therapy. In some patients they occur only once or twice (if at all) and
with others continue throughout the course of treatment, usually lessening
in severity. They can occur and are more often described in cycles
(example: every 4 weeks) and have been reported to last from days to
Herxheimer Reactions can be very difficult on patients and affect compliance with therapy so supportive measures should be sought or utilized to lessen discomfort if needed. The use of aspirin, NSAIDs (non steroidal anti inflammatory drugs), pain medication, muscle relaxers, hot baths or others remedies can be appropriate. Of note, some have found Benedryl helpful even in the absence of rash or hives.
The good news:
The good news is that the Herxheimer is thought to indicate that the antibiotics are indeed working. In the cyclic nature of recovery it is seen that following each worsening there may be more improvement. However the lack of Herxheimer Reaction is not cause to be anxious if symptoms are improving.
Info is from: http://www.angelfire.com/biz/romarkaraoke/Herx.html