The cause for itching in systemic diseases could be the result of an alternation in the local biochemical environment of the free nerve endings in the skin which transmit the itch sensation to the central nervous system.
Skin and Systemic Changes in Prolonged Itching
The incessant scratching induced by the itch-scratch cycle can cause localized and general changes in individuals.
- Local changes due to scratching are scratch marks, bleeding, broken hair, thickening and darkening of the skin, bleeding under the skin at times and, shiny finger nails. At times, the broken skin may become secondarily infected with bacteria.
- Generally, the effected person may show irritability and become exhausted because of lack of sleep and stress. Severe cases of depression have occurred after prolonged bouts of incessant itchiness of the skin.
Systemic Causes of Itching
Diagnosis of itching due to skin diseases is comparatively easy for the discerning eye. But when the itching occurs without evidence of any primary skin disease, but with evidence of the itch and the after-effects of scratching, then systemic causes for the itchy skin should be checked for. Possible systemic causes include:
- Kidney Disease. More than 80% of chronic renal failure patients experience generalized itching. This has no correlation with degree of kidney damage and only some patients get relief from the itching following hemodialysis.
- Systemic diseases like liver diseases, iron deficiency anemia and endocrine diseases like hyper and hypo-thyroidism are sometimes associated with intractable itchy skin.
- Internal Cancer. Any generalized itching without skin rash should be investigated to rule out underlying malignancies. Characteristic itching, mainly on the legs, is the presenting symptom in about 25% of cases of Hodgkin’s lymphoma. Itching is also intense in carcinoid tumors which release serotonin and bradykinin, the itch producing chemical mediators.
- In tropical countries, intestinal and tissue parasitic infections like roundworm, amoebiasis, hydatidosis and onchocerciasis should be ruled out in cases of generalized itching. Pin worm infestation is the main cause for nocturnal perianal itching in children.
- Medications cause various degrees of itching through various mechanisms. Testosterones erythromycin estolate, tolbutamide, phenothiazine and progesterone cause bile retention in liver (cholestasis) and thus generate pruritus. Allergic hypersensitivity and non allergic irritant reactions to medications are also responsible for many instances of itchy skin. Morphine and other opioids produce severe itchiness through both central and peripheral mechanisms.
- HIV infection can present as generalized itching with or without skin rashes.
- Persistent itching is at times a manifestation of post menopausal syndrome.
Psychogenic Itching
Psychological disturbances can present as localized or generalized itchy skin. Unless the patient has very evident psychiatric symptoms the diagnosis of psychogenic itching is made through a process of exclusion of systemic and skin diseases. Anogenital pruritus is typically psychogenic in origin most of the time.
It is evident that correct diagnosis of the cause of generalized itching is mandatory for proper treatment of the itchy skin.
Related Reading
- How Does Itching Occur?: How Scratching Relieves the Itch. It would be interesting to know how itching occurs in skin and systemic diseases and how the act of scratching relieves the itch.
Reference
- Patrick Yesudian. Pruritus. IADVL Textbook and Atlas of Dermatology, 1994, Bhalani Publishing House, Mumbai.
- Greaves MW. Pruritus. Rook’s Textbook of Dermatology, 7th Edition, 2004
Disclaimer
The information given in this article is for educational purposes only so that patients are aware of the options available. No diagnosis should be made or treatment undertaken without first consulting your doctor. If you do so, the author or Suite101 will not be responsible for any consequences. The images provided are for illustration purpose only.
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