Postherpetic itch is a complication of shingles wherein the affected area of the skin continues itching long after the shingles virus is eradicated, according to Ross Labs. Some doctors believe this itch may be caused by hyperactivity of the nerve fibers that were damaged by the shingles virus.
Postherpetic itch is sometimes considered an uncommon symptom of postherpetic neuralgia, explains Mayo Clinic. Postherpetic neuralgia is a medical complication in which nerve fibers that were damaged during a bout of shingles cause chronic pain that lasts for over three months and can last for years. Postherpetic itch causes chronic itching and numbness at the shingles site and is most common in patients who are older than 50 and have had a severe case of shingles on the face or torso. Pre-existing conditions such as diabetes may also increase the likelihood of developing postherpetic itch or neuralgia.
In reported cases of postherpetic itch, 95 percent of sensory receptors in the damaged nerves are destroyed, while the remaining 5 percent appear hyperactive. The small percentage of remaining nerve fibers likely cause the chronic itch, notes Ross Labs. Patients with severe postherpetic itch are at risk of injuring themselves with incessant scratching. As of 2015, treatment options for postherpetic itch are mostly limited to topical anaesthetics.