Generalized Itching / Pruritis / Prurigo
Often the cause of itchy skin is not known or is unclear as itching is characterisitc of many skin conditions and systemic diseases.
Pruritis may be generalized (that may involve large areas of the body) or localized (restricted to a specific area).
Generalized pruritis also indicates "itching" that cannot be readily associated with a detectable primary skin condition such as eczema. Secondary features often involve severe excoriation (bloody scratches) that affect all sites except for the mid-back as this area cannot be reached by the patient. This pattern is called the "butterfly" sign. Most patients generally appear to have fine, dry and scaly skin and the itching usually responds well to the application of emollients.
Approximately half of the patients who suffer from pruritis may have some underlying systemic disease e.g. uremia, lymphomas, leukemias, iron deficiency and pregnancy etc. Other causes may be due to parasitic or fungal infestations, takingor cessation of drugs and psychological factors.
Localized pruritis is usually caused by skin friction either against close fitting clothing or skin to skin. Other causes may be fungal or parasitic infestations.
* more common in adults, especially the elderly.
* no primary rash is usually evident.
* most rashes are usually secondary due to scratching.
* itching is usually worse at night.
* secondary lesions e.g. scratch marks, crusts, "eczematoid" type lesions or lichenification may occur as the direct result of scratching.
* systemic causes vary from patient to patient.
* some patients will have no obvious underlying abnormalities.
* psychological factors e.g. depression, anxiety or stress can trigger or aggravate the condition.
Prurigo Nodularis is a general term applied to a range of unconnected itchy skin condiitions involving excoration of the skin accompanied by thickening of the skin or the development of nodules as a result of scratching.
Onset of prurigo nodularis is usually gradual and mainly involves the arms and leags and occassionaly the back. The skin lesions present as pale red papules that develop into hemispherical nodules. The nodules may be few and widely spaces or numerous. Often they appear in a linear formation following the lines of repeated scratching. This condition is often chronic.
* is usually seen in middle-aged women.
* discrete nodules, 5-30mm in diameter, most commonly present on the extensor aspects of the limbs due to scratching.
* the original cause of the scratching is often obscure, however, some patients may have a background skin condition such as eczema or chronic pruritis.
* it is often considered to be a "nodular" form of Lichen simplex.