Pruritus, or itching, is one of the most common symptoms in dermatology. Itch sensation is transmitted to the central nervous system by C-fibers (which are distinct from C-fibers that transmit pain signals) and can be very disruptive to a patient's quality of life. Pruritus is commonly associated with a variety of skin diseases, yet it may also be seen independent of skin pathology. When first evaluating pruritus, it is important to establish if the itch is secondary to an inflammatory skin condition or present without a primary rash.
Several inflammatory skin diseases are associated with pruritus, including atopic dermatitis, contact dermatitis, lichen planus, and urticaria. Significant pruritus is also associated with burns and healing skin, and in xerotic, or dry skin, especially in older patients.
When pruritus occurs in the absence of skin findings, a variety of systemic diseases should be considered. Uremic pruritus is common in patients with chronic or end-stage kidney disease. It typically presents within 3 months of starting hemodialysis. Pruritus can also be associated with cholestatic hepatobiliary diseases (Figure 90). Pruritus associated with cirrhosis from alcoholic liver disease or hepatitis C infection can occur in the absence of cholestasis. Thyroid disease and polycythemia vera are other systemic diseases that might present with itching. Generalized pruritus may also be the presenting symptom in malignancies such as lymphocytic leukemia and Hodgkin lymphoma. Certain infections, such as HIV, may present with generalized itching as well.
Various psychiatric or somatization conditions can also manifest as itching (psychogenic itch) (Figure 91). Pruritus typically worsens during stressful or traumatic events. Patients with chronic pruritus have increased depression and impaired quality of life. Neuropathic pruritus describes the itch that is caused by dysfunction of a peripheral or central nerve(s) due to surgery, trauma, arthritis, neuropathy, or infection (postherpetic neuralgia). Neuropathic itch is often localized to a small, well-circumscribed area; examples include the forearm (brachioradial pruritus), posterior shoulder, or mid to upper back (notalgia paresthetica) (Figure 92).
A review of systems, complete blood count, thyroid function studies, kidney function tests, liver chemistry tests, HIV test, and chest radiograph are necessary to help guide further workup. In addition, a review of the patient's medications, including supplements and illicit drugs, should be performed. Common medications that can cause pruritus are opiates, calcium channel blockers, hydrochlorothiazide, and NSAIDs (Table 17).
Patient education is critical to the management of any pruritic condition. The primary lesson for most patients is scratching causes skin damage that contributes to an “itch-scratch-itch” cycle. Treatment of pruritus is directed at addressing the underlying cause. The treatment of inflammatory skin conditions with topical glucocorticoids and emollients can help alleviate pruritus. Topical anti-itch medications containing menthol can also be helpful. First-generation oral antihistamines can be sedating and helpful for pruritus at night. For older patients with xerotic skin, comprehensive dry skin care should be reviewed. This includes bathing in warm water followed by immediate application of a thick emollient. Products that contain perfumes or dyes should be avoided as xerotic skin is at greater risk of irritation due to a compromised skin barrier.
Topical treatments may not be as effective for systemic causes of pruritus. Gabapentin can be effective in treating pruritus associated with burns, neuropathic itch, and uremic pruritus. Phototherapy can also be used for uremic pruritus. Ursodeoxycholic acid can be considered for cholestatic pruritus.