A. Introduction. Itching can be caused by a variety of dermatologic and nondermatologic disorders.
a. Dermatologic disorders. Pruritus is the primary symptom in a wide range of inflammatory skin diseases such as atopic dermatitis, psoriasis, and chronic urticaria. Primary skin lesions are usually present in addition to secondary changes from rubbing and scratching.
b. Systemic disorders. When pruritus occurs without primary skin findings, systemic disorders such as uremia, lymphoma, hepatic diseases, and HIV infection should be considered.
B. Causes of Pruritus
a. Dermatologic disorders
i. Xerosis (dry skin). Often seen in older adults, especially on the lower legs and feet.
ii. Parasitic infestation (e.g., scabies, pediculosis) and insect bites.
iii. Other causes include urticaria, atopic or contact dermatitis, eczematous dermatitis, superficial fungal infections, drug reactions, dermatitis herpetiformis, fiberglass dermatitis, lichen planus, cutaneous T cell lymphoma, and folliculitis.
b. Systemic disorders
i. Uremia is the most common systemic cause of pruritus in the absence of primary skin lesions.
ii. Primary biliary cirrhosis, extrahepatic biliary obstruction, and cholestatic drugs cause total bilirubin elevation, bile salt retention and deposition into skin, and resulting pruritus.
iii. Cancer. Consider lymphoma (especially Hodgkin’s disease), breast, lung, and stomach cancer.
iv. Hematologic disorders. Polycythemia vera (and the other myeloproliferative disorders) and iron deficiency anemia.
v. Endocrine disorders such as diabetes mellitus, hyperthyroidism and hypothyroidism, and carcinoid syndrome are associated with variable itching.
vi. Infection. Pruritus is among one of the most common skin manifestations of HIV infection and can occur as a primary symptom of HIV. Other causes in HIV-infected patients may include eosinophilic folliculitis and insect bite hypersensitivity reaction. In HIV-positive patients, pruritus may also relate to skin conditions that are more prevalent or directly aggravated by HIV infection (e.g., psoriasis, seborrheic dermatitis, skin dryness).
vii. Neurologic. Pruritus can occur with primary damage to nerve fibers (e.g., postherpetic neuralgia), spinal nerve root injuries (e.g., brachioradial pruritus, notalgia paresthetica), and injury to afferent nerves (e.g., post-stroke).
ix. Drugs (e.g., opioids, β-blockers, captopril, retinoids)
MNEMONIC: Common Causes of Pruritus (“ITCHING in ED”)
Infestation (e.g., scabies)
Total bilirubin elevation (e.g., primary biliary cirrhosis)
Chronic renal failure (uremia) or Cancer
Dermatologic disorders or Drugs
C. Approach to the Patient
a. Patient history. A detailed history focusing on medications, medical conditions, travel, hobbies, occupation, and the presence of constitutional symptoms (e.g., weight loss, fever) is important.
i. Nocturnal generalized pruritus with chills, sweating, and fever are concerning for Hodgkin’s disease.
ii. Patients with scabies usually experience itching out of proportion to skin findings. The diagnosis should be considered especially when multiple family members are affected.
iii. Polycythemia vera is often associated with a “prickly” itch that often occurs as the patient cools off after bathing.
iv. Xerosis is common in older adults, especially during winter months and hot air exposure.
v. Psychogenic pruritus rarely interferes with sleep, as opposed to other pruritic conditions.
b. Physical examination. A thorough dermatologic examination of the skin, scalp, nails, hair, mucous membranes, and anogenital area is recommended. Assess for primary (e.g., papules, vesicles) and secondary (e.g., crusting, erosion) changes, evidence of xerosis, dermographism (i.e., stroking the back and watching for subsequent skin wheal), and skin signs of systemic diseases (e.g., jaundice in liver disease, hyperpigmentation and clubbing in hyperthyroidism). It is important to determine whether a primary dermatologic process is present and the source of symptoms (e.g., scaly plaques of atopic dermatitis, vesicles and erosions in dermatitis herpetiformis, and linear burrows of finger/toe web spaces and nodules in the scrotum in scabies). Excoriations in the absence of a rash indicate the need to consider a systemic cause (e.g., uremia, cirrhosis). A general physical examination—enlarged lymph nodes, liver, or spleen, for example—may identify an undiagnosed systemic cause of generalized pruritus.
c. Diagnostic tests. If the history and physical examination fail to reveal a cause for the patient’s pruritus, then blood tests (e.g., a complete blood count [CBC] with differential, bilirubin, alkaline phosphatase, thyroid-stimulating hormone [TSH], and creatinine levels) and a chest radiograph should be considered. Biopsy of the skin should be reserved for patients with persistent symptoms without an obvious cause.
a. Discontinuation of culprit medications, especially those known to cause release of histamine (e.g., opiates, nonsteroidal antiinflammatory drugs).
b. Antihistamine therapy, especially if the pruritus is caused by histamine release (e.g., urticarial or drug eruptions). Nonsedating loratadine or cetirizine (10 mg orally daily) may provide symptomatic relief. Hydroxyzine (25 mg orally every 4–6 hours) and other sedating antihistamines are also helpful through their sedating/tranquilizing properties.
c. If the cause of the pruritus is not evident, empiric treatment for xerosis with a 2-week course of emollients (e.g., Aquaphor) and use of a mild soap (e.g., Dove). Coolants such as menthol (e.g., Sarna) and topical anesthetics such as pramoxine (e.g., Sarna Sensitive) and topical capsaicin may also be helpful when treating a localized neuropathic itch.
Suggested Further Readings
Combs SA, Teixeira JP, Germain MJ. Pruritus in kidney disease. Semin Nephrol 2015;35:383–91.Find this resource:
Leslie TA. Itch management in the elderly. Curr Probl Dermatol 2016;50:192–201.Find this resource:
Tajiri K, Shimizu Y. Recent advances in the management of pruritus in chronic liver diseases. World J Gastroenterol 2017;23:3418–26.Find this resource:
Tarikci N, Kocatürk E, Güngör S, et al. Pruritus in systemic diseases: a review of etiological factors and new treatment modalities. Sci World J 2015;2015:8.Find this resource: