How to assess and relieve that perplexing rashless itch

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doi:10.12788/jfp.0096

Applied Evidence

How to assess and relieve that perplexing rashless itch

J Fam Pract. 2020 November;69(9):430-437 | 10.12788/jfp.0096

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References

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Psychogenic pruritus

Chronic pruritus can be a comorbidity of psychiatric illness. A retrospective study found that pruritus occurs in 32% to 42% of psychiatric inpatients.¹⁴ Depression, anxiety, bipolar disorders, obsessive–compulsive disorders, somatoform disorders, psychosis, and substance abuse all have a strong link to psychogenic excoriation.¹⁵ Psychogenic excoriation, which can cause secondary skin lesions, occurs in psychiatric patients who excessively pick and scratch normal skin because they perceive an itch sensation or have a delusion of infestation.² Affected skin can be marked by scattered crusted lesions (FIGURE) anywhere on the body that the patient can reach—most commonly, the extremities.²

Delusion of infestation. Patients with a delusion of infestation have a strong belief that their body is infected by some kind of insect or microorganism.¹⁶ Before a diagnosis of delusion of infestation can be made, other organic causes must be excluded, including withdrawal from such substances as cocaine, amphetamines, and alcohol.¹⁶ Patients with a delusion of infestation can have, and maintain, a symptomatic response with continuing use of an atypical antipsychotic agent, including risperidone and olanzapine.¹⁷

Evaluation and diagnostic work-up

A thorough medical history, review of systems, medication review, social history, and family history are important when evaluating a patient with chronic pruritus.¹⁸ These items can be valuable in formulating a differential diagnosis, even before a physical examination.

Physical examination. The physical exam should include detailed inspection of the entire skin and hair¹⁸; such a comprehensive physical exam can determine whether the source of the itch is cutaneous.⁷ This, in turn, can help further narrow the differential diagnosis. It is crucial that the physical exam include palpation of the liver, spleen, lymph nodes, and thyroid for organomegaly,⁸ which could indicate a serious systemic condition, such as lymphoma.

The ice-pack sign—in which an ice pack applied to the pruritic area provides immediate relief—is considered pathognomonic for brachioradial pruritus.

The ice-pack sign—in which an ice pack is applied to the pruritic area, the patient experiences immediate relief of pruritus, and the itch returns soon after the ice pack is removed—is considered pathognomonic for brachioradial pruritus.¹⁹

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