Persistent itching can be a stubbornly distressing symptom. Many skin and systemic disorders can precipitate itching, which is caused by stimulation of specialized nerve fibers found only in the skin. Although the precise mechanisms by which certain disorders cause persistent itching are poorly understood, it's clear that treatment of the underlying condition often improves itching symptoms.
Lice
Lice are parasitic insects that can infest the head, body or pubic area. These insects feed on human blood. Their bite causes an allergic skin reaction that leads to intense itching. Lice spread via close personal contact; they do not fly or jump. According to the Centers for Disease Control and Prevention, the body louse can transmit diseases including trench fever, epidemic relapsing fever and epidemic typhus. Clearance of lice infestation eliminates the itching caused by these parasites.
Peripheral Neuropathy
The peripheral nerves are those beyond the brain and spinal cord. It's through these nerves that the brain communicates with all parts of the body and vice versa. Peripheral neuropathy is a general term describing a disorder affecting the peripheral nerves. Peripheral neuropathies that involve sensory nerves can cause a variety of abnormal sensations, including itching. The University of Chicago Center for Peripheral Neuropathy reports a wide variety of causes of sensory peripheral neuropathies that may trigger itching including toxins, medications, infections, autoimmune diseases and diabetes.
Hodgkin's Lymphoma
Hodgkin's lymphoma is a form of white blood cell cancer. The Leukemia and Lymphoma Society reports itching may be an early symptom of Hodgkin's lymphoma. In the seminal cancer text "Clinical Oncology," Dr. Joseph Connors of the British Columbia Cancer Agency says itching may pre-date a diagnosis of Hodgkin's lymphoma by a year or more.
Kidney Failure
People with advanced chronic kidney disease and those on kidney dialysis frequently suffer from persistent itching termed uremic pruritus. In a 2007 article published in the journal Kidney International, Dr. S. Keithi-Reddy and colleagues reported uremic pruritus occurs in 50 percent to 90 percent of people with advanced or end-stage kidney failure. Itching associated with kidney failure can be local or generalized. It may be severe and is often difficult to alleviate.
Liver Diseases
Liver diseases that cause an accumulation of chemicals called bile salts in the blood often trigger persistent generalized itching. In a review article published in Acta Dermatovenerologica, Dr. V. Peharda and colleagues noted hepatitis B and C, alcoholic cirrhosis, autoimmune hepatitis, primary biliary cirrhosis and bile duct cancer commonly cause persistent itching.
