Itching (Pruritus)
Pruritus or itching has many potential causes. Severe and persistent itching can lead to difficulty sleeping, anxiety and depression. The sensation of pruritus is carried by slow-conducting nerves and mediated by several small molecules including histamine, substance P, serotonin and bradykinin. Itching can be related to irritants or allergens, skin rashes, systemic diseases as well as abnormal processing of the itching impulse in the central nervous system.
What are some of the common causes of pruritus?
- Atopic dermatitis
- Urticaria (hives)
- Varicella (chicken pox)
- Dry skin (“winter itch”)
- Scabies
- Head or body lice
Although itching is frequently accompanied by a rash or dry skin, itching can occur in the absence of any visible abnormality of the skin.
What are some internal conditions and infections that can cause itching?
Widespread itching may be a manifestation of an underlying, internal disorder. Kidney failure, for example, often causes severe, widespread, intractable itching and is known as uremic pruritus. Some forms of liver disease including cholestasis and cholecystitis, as well as viral hepatitis, and thyroid dysfunction can cause the skin to itch. Certain disorders of the blood including lymphomas (cancer of the lymphatic system), leukemias (cancer of the blood or bone marrow), anemia (low red blood cell count), polycythemia vera (high red blood cell count), multiple myeloma (cancer of the immune system), and neurologic conditions such as pinched nerves can cause itching. Infectious diseases including HIV, varicella zoster virus (the cause of post-herpetic neuralgia) and skin boils due to methicillin sensitive or resistant staphylococcus aureus (a form of bacteria) can cause severe itching.
What can be done for pruritus?
Often the dermatologist will be able to diagnose the cause of itching with a careful history and physicial examination; however, to determine a specific cause of the itch, a panel of blood tests, skin scraping, or biopsy may be needed to help make the diagnosis.
If the itch is due to a skin disease or skin infection, treatment of the causative condition itself, in combination with topical medications and oral antihistamines usully relieves the symptoms. If the itch is secondary to an internal disease, patients may require treatment of the disease with oral medications. Patients with widespread pruritus often benefit greatly from ultraviolet light therapy.
Simple measures that can relieve itching include:
- Moisturizers or bath powders containing oatmeal extract
- Topical lotions or creams with menthol, camphor or calamine
- Over-the-counter anti-itch creams containing hydrocortisone
- Mild, hydrating cleansers
- Application of cold water compresses for localized areas of itching
- Wearing light, loose-fitting clothing and staying cool
If these simple measures are inadequate to relieve your itching or an underlying cause of the itching is not apparent, consult your dermatologist.