is an itch that occurs in response to the herpes zoster virus, or shingles. and thus infect the corresponding area of skin associated with the nerve, or . Due to the infection’s affecting only a particular set of nerves and subsequent , .
The shingles rash typically subsides in three to four weeks, and the person recovers. But there are two common complications of shingles affecting up to 30% of people with shingles: 1) (an aching, burning, or stabbing pain) that most commonly afflicts people 50 years or older; and 2) . The underlying mechanism causing postherpetic neuralgia, or pain, is thought to be spontaneous pain receptor activity and can be treated with skin patches (local anesthetic), tricyclic antidepressants, anticonvulsants, and opioid painkillers.
Though a less common aftermath of shingles, is debilitating and more difficult to treat than postherpetic neuralgia. The underlying mechanism of why the itch persists is unknown. However, in cases of itch, in the nerves afflicted with shingles, . One possible explanation for the extreme itching could be that the 5% of nerve fibers remaining alive are the ones that mediate itch. Another possibility is that the hyperactivity of the remaining 5% of the nerve fibers is being misinterpreted at some point as the sensory information is relayed to the brain.
“A cluster of small bumps (1) turns into blisters (2) that resemble chickenpox lesions. The blisters fill with pus, break open (3), crust over (4), and finally disappear. itch and neuralgia (pain) are caused by damage to the nerves (5).” http://www.fda.gov/fdac/features/2001/301_pox.html
Sometimes we deal with itch that just won’t seem to stop. This is especially true in patients suffering from shingles whose skin sensory neurons have been damaged. These patients scratch for relief, but in desperation injure themselves without being aware of it. In some documented cases, a relentless itch has persisted for years, resulting in serious injury as the patient repeatedly scratches the same area of the body. In one case, a 10-year-old boy’s neck was damaged and in another case a 40-year-old woman’s shoulder injured, all from their own scratching.
, but specific treatments are now being developed. Currently, treatment consists of topical local anesthetics to numb the skin at the location of the itch. This treatment has risks: when an area of skin is numb to itch, it is also numb to pain, leaving the patient unaware of, and therefore exposed, to injuries.
This lack of a specific treatment for itch can be a major problem. Many patients get relief from topical anesthetics, but others with severe itch continue to suffer. An extreme case of itch, documented in 2002, illustrates how far a patient may be driven by relentless itch. The shingles virus caused nerve damage and skin desensitization in a 39-year-old woman. Because she felt but not pain, she painlessly scratched right through her skull into her brain, despite her head and her hand being swathed in bandages as a way to control scratch-induced damage. In an interview with Atul Gawande, she said, “I don’t normally tell people this, but I have a fantasy of shaving off my eyebrow and taking a metal-wire grill brush and scratching away.” (Read Her Full Story)
When it comes to research, and the treatment of itch has been sidelined, with most of the effort going to and alleviating pain. In spite of some similarities between itch and pain pathways, . Research is currently being conducted on potential targets including , PAR2 and GRPR antagonists, as well as a new oral kappa-opiod receptor agonist, , which is in . But much more research is needed to investigate the neural circuitry and mechanisms of itch and eventually find innovative treatments for chronic itch.
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2. Johnson, RW & Dworkin, RH. 2003. “Clinical review: Treatment of shingles and postherpetic neuralgia”. BMJ.
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4. Stankus SJ, Dlugopolski M, Packer D. 2000. “Management of shingles (shingles) and postherpetic neuralgia”. Am Fam Physician.
5. National Institute of Neurological Disorders and Stroke. 2011. “Shingles: Hope Through Research.” National Institute of Health.
6. Mayo Clinic Staff. 2010. “Postherpetic neuralgia: Treatments and Drugs” Mayo Clinic.
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11. Jagdeo J & Kroshinsky D. 2011. “A case of post-herpetic itch resolved with gabapentin”. JDD.
12. Eastman P. 2011. “New Research Shows Itch is A Lot More than Skin Deep”. Neurology Today.
13. Gawande, Atul. “The Itch.” The New Yorker. June 2008. April 2012