Pruritus

(Itching)

An unpleasant sensation that instinctively elicits attempts to scratch or rub.

Pruritus is a common complaint among the elderly and is usually caused by xerosis (dry skin). Other local causes include subtle contact dermatitis, candidal infection, scabies, and pediculosis (see Table 123-4). Systemic disorders that cause generalized pruritus in the absence of primary skin lesions (accounting for 10 to 50% of cases) include liver disease, uremia, iron deficiency anemia, lymphomas, leukemias, polycythemia vera, HIV infection, and parasitosis (usually of the gastrointestinal [GI] tract). Less common causes include diabetes mellitus, hyperthyroidism, and solid malignancies. Some drugs (eg, barbiturates) can cause pruritus. Although drug-induced pruritus is usually accompanied by a rash, some drugs (eg, opioids) often do not produce visible clinical findings.

Diagnosis

The history should focus on exacerbating factors, review of systems, and drug history.

In the absence of an obvious skin disease, a systemic disorder (eg, lymphadenopathy, hepatosplenomegaly, jaundice, anemia) should be suspected, particularly when pruritus begins suddenly and is severe and unrelenting. Although the complaint of a hot shower exacerbating pruritus is common regardless of the underlying cause of the pruritus, this symptom may indicate polycythemia vera.

Laboratory tests include a complete blood cell count; ESR; measurement of electrolyte, urea, and thyroid-stimulating hormone levels; and blood glucose and liver function tests. Stool should be tested for blood, ova, and parasites if indicated by history or examination.

Treatment

All patients complaining of pruritus should be treated for xerosis, because even mild dryness can exacerbate pruritus, regardless of cause. Patients should also be advised to avoid very hot baths or showers, rubbing alcohol, and irritants such as harsh detergents. Washing should be done no more than once a day, with soap used only on body folds and dirty areas. The use of opioids or other drugs suspected of causing the pruritus should be discontinued, if possible. Antihistamines and major tranquilizers are often prescribed for pruritus, but they pose danger to the elderly and rarely produce a benefit that justifies the risk. Phototherapy, if not contraindicated, can be tried for pruritus unresponsive to other measures.