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Prurigo

What Is It, Causes, Signs, Symptoms and More

Author:Lily Guo

Editors:Alyssa Haag,Emily Miao, PharmD,Kelsey LaFayette, DNP, ARNP, FNP-C

Illustrator:Jessica Reynolds, MS

Copyeditor:Stacy M. Johnson, LMSW


What is prurigo?

Prurigo, also known as prurigo nodularis (PN) or nodular prurigo, refers to a chronic skin disorder characterized by multiple, firm, and pruritic (i.e., itchy) nodules arranged in a symmetrical distribution across the body. A nodule is described as a well-circumscribed, elevated, solid lesion. In PN, the nodules can range anywhere from a few millimeters to greater than ten millimeters in diameter. Prurigo is a rare condition that primarily affects older individuals and is often chronic, lasting years. It is rare for the lesions to resolve completely and they often return even after the scratch-itch cycle has resolved. The scratch-itch cycle refers to a sensation of itchiness causing the individual to scratch, which then causes the inflammation and rash to exacerbate and itch further. Prurigo is not contagious or hereditary. It is estimated to affect 72 per 100,000 people in the United States and occurs in all genders equally. It can affect quality of life across all age groups but is more common in the elderly, with a median age of 62. 

Itchy skin lesions.

What causes prurigo?

The exact cause of prurigo is currently unknown, however it occurs in those who have chronic pruritus and is frequently associated with atopic dermatitis, also known as eczema. Eczema is a skin condition that results in inflamed, irritated, and itchy skin. Prurigo arises as a result of continuous scratching over a prolonged period of time.  Several systemic and psychiatric diseases can be associated with severe pruritus. Examples of systemic diseases associated with prurigo include diabetes mellitus, chronic renal failure, cardiovascular disease, hepatitis C, and gluten enteropathy. Prurigo is seen in some individuals with HIV infection, especially if their immune system is severely compromised. The exact role of these underlying conditions in prurigo is unclear. Anxiety and depression, as well as general emotional stress can also cause prurigo. 

Several mechanisms have been proposed for the cause of prurigo including an increased number of nerve fibers in the skin in those with prurigo. Nerve growth factor  (NGF), a neuropeptide, has been found to be overexpressed in prurigo lesions, and is involved in the release of substance P, which stimulates inflammation. Prurigo has also been thought of as a small fiber neuropathy, which is a disorder in which the small sensory cutaneous nerves are affected. Studies have found that the nerve fiber density in the skin of those with prurigo is reduced, potentially leading to sensory disturbances and itch. Lastly, Th2 cytokines have been shown to be increased in the skin of those with prurigo. Cytokines are small proteins important for cellular signaling. Th2 cytokines specifically, play an important role in the pathophysiology of allergic diseases, including asthma. Additionally, IL-31, a potent cytokine involved in pruritus, is aberrantly expressed in prurigo nodularis. 

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What are the signs and symptoms of prurigo?

The signs and symptoms of prurigo include intense itching of firm, dome-shaped nodules that are typically symmetrically distributed on the extensor surfaces of the arms and legs; upper back; abdomen; and the sacrum. Notably, prurigo nodularis spares the upper-mid back between the shoulder blades in a pattern termed the “butterfly sign.” The palms, soles of the feet, face, and flexural areas, such as the armpit or creases of the arms and legs, are typically spared. The nodules can range in size from a few millimeters to several centimeters and can be flesh colored, erythematous, brown or black. An individual can have a few nodules on their body or up to hundreds. The pruritus associated with prurigo is often severe and distressing. Pruritus can be intermittent and sporadic, or continuous. Oftentimes the itching is exacerbated by heat, sweating, and wearing tight or irritating clothing. 

How is prurigo diagnosed?

Prurigo is diagnosed based on a thorough interview and history, along with a physical exam. The individual may report a longstanding history of severe itching. On physical examination, prurigo characteristically presents with nodular lesions that are usually symmetrically distributed. They can be excoriated, defined by loss of the upper layer of the dermis as a result of scratching. 

While a skin biopsy is not routinely performed to confirm the diagnosis of prurigo, it may be indicated in cases where the clinical diagnosis is uncertain or the typical treatments for prurigo do not work. A skin biopsy can be used to test for other skin diseases that can have similar presentations, such as bullous pemphigoid. Immunofluorescence studies and enzyme-linked immunosorbent assay (ELISA) are two laboratory tests that can be ordered to detect the presence of circulating autoantibodies against bullous pemphigoid. Systemic causes of chronic pruritus should be considered, especially if the individual does not have a history of atopic dermatitis or other pruritic skin conditions. Laboratory tests including a complete blood cell count; liver function tests; blood urea nitrogen and creatinine; thyroid-stimulating hormone; HIV testing; urinalysis; stool examination for ova and parasites. A chest X-ray may be ordered to rule out systemic causes of extreme pruritus (e.g., chronic kidney disease, liver disease, thyroid disease, HIV infection, parasitic infestation, and malignancy). 

How is prurigo treated?

Treatment of prurigo includes topical and systemic therapies aimed at treating the symptoms, interrupting the scratch-itch cycle, and flattening the nodules. The individual with prurigo may also be educated on general techniques to reduce skin irritation and stop scratching. One with prurigo can adopt certain skin care habits to help alleviate the symptoms, which include using mild and gentle cleansers while bathing or showering, and applying topical emollients (i.e., moisturizers) many times a day. Those with prurigo should keep their nails short and wear gloves at night to minimize scratching, and wear occlusive bandages and dressings to prevent excoriation. Calamine lotions, and lotions containing menthol, camphor, or pramoxine hydrochloride can provide additional relief due to their ability to provide anesthetic and cooling effects to the skin. Other topical treatments that have been used with some success include topical capsaicin cream; topical calcineurin inhibitors (e.g., tacrolimus, topical pimecrolimus); and topical vitamin D analogues (e.g., calcipotriol, tacalcitol). 

Antihistamines (e.g., hydroxyzine, diphenhydramine) used at bedtime can have a sedating and anti-inflammatory effect helpful for controlling nocturnal pruritus. Selective serotonin reuptake inhibitors (e.g., sertraline, fluoxetine) and tricyclic antidepressants (e.g., amitriptyline) are also used for chronic pruritus. These are especially helpful when a component of depression is present, potentially leading to increased pruritus. 

For those with only a few large nodular lesions, topical corticosteroids, such as clobetasol dipropionate 0.05% or betamethasone valerate 0.1% ointment, can be used. These are applied under occlusion with plastic wrap at night for at least two to four weeks. In addition to topical application, injecting corticosteroids (such as triamcinolone acetonide) into the lesion once a month is also shown to be effective in reducing pruritus and flattening the nodules. 

For those with widespread disease that do not respond to corticosteroids, phototherapy with narrowband ultraviolet B light has been shown to be effective. It can be used in combination with topical corticosteroids. If phototherapy fails, other systemic medications may be warranted including immunosuppressants (e.g., low-dose methotrexate, oral cyclosporine) and cancer drugs (e.g., thalidomide, lenalidomide). However, these medications are associated with multiple toxicities (e.g., birth defects for individuals who are pregnant, sensorimotor peripheral neuropathy, renal failure) and are generally used as a last resort option in treating those with chronic prurigo. 

What are the most important facts to know about prurigo?

Prurigo is a rare and chronic skin condition characterized by multiple pruritic, firm nodules that are symmetrically distributed across the arms, legs, and trunk of the body. It commonly spares the upper mid-back, palms, soles, and flexor surfaces. While the cause of prurigo is unknown, it is commonly associated with atopic dermatitis and other conditions that lead to pruritus. Several mechanisms of prurigo have been proposed including cytokine abnormality, increased nerve fiber count, and an association with small fiber neuropathies. Diagnosis primarily relies on taking a thorough history of symptoms and a physical examination. Skin biopsy is not routinely done, but can be used to rule out other similar conditions. Laboratory studies can be conducted as well to rule out systemic conditions, including infection, chronic kidney disease, liver disease, and thyroid disease. Treatment starts with behavioral modifications including use of gentle skin cleansers, wearing gloves at night to prevent itching, and wearing occlusive bandages. Medications can help manage symptoms, including antihistamines and corticosteroids. If corticosteroids fail to resolve the symptoms, phototherapy and systemic immunosuppressants have been used. 

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Related links

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Resources for research and reference

Katayama, I., Miyazaki, Y., & Nishioka, K. (1996). Topical vitamin D3 (tacalcitol) for steroid-resistant prurigo. The British Journal of Dermatology, 135(2): 237–240. 

Lee, H. G., Grossman, S. K., Valdes-Rodriguez, R., Berenato, F., Korbutov, J., Chan, Y. H., Lavery, M. J., & Yosipovitch, G. (2017). Topical ketamine-amitriptyline-lidocaine for chronic pruritus: A retrospective study assessing efficacy and tolerability. Journal of the American Academy of Dermatology, 76(4), 760–761. DOI: 10.1016/j.jaad.2016.10.030

Rowland Payne, C. M., Wilkinson, J. D., McKee, P. H., Jurecka, W., & Black, M. M. (1985). Nodular prurigo--a clinicopathological study of 46 patients. The British Journal of Dermatology, 113(4): 431–439. DOI: 10.1111/j.1365-2133.1985.tb02357.x

Siepmann, D., Lotts, T., Blome, C., Braeutigam, M., Phan, N. Q., Butterfass-Bahloul, T., Augustin, M., Luger, T. A., & Ständer, S. (2013). Evaluation of the antipruritic effects of topical pimecrolimus in non-atopic prurigo nodularis: results of a randomized, hydrocortisone-controlled, double-blind phase II trial. Dermatology, 227(4): 353–360. DOI: 10.1159/000355671

Ständer, S., Schürmeyer-Horst, F., Luger, T. A., & Weisshaar, E. (2006). Treatment of pruritic diseases with topical calcineurin inhibitors. Therapeutics and clinical risk management, 2(2): 213–218. DOI: 10.2147/tcrm.2006.2.2.213

Watsky, K., Fowler, J., Corona, R. (2022). Prurigo Nodularis. In UpToDate. Retrieved June 15, 2022, from https://www-uptodate-com.rosalindfranklin.idm.oclc.org/contents/prurigo-nodularis?search=prurigo&source=search_result&selectedTitle=1~42&usage_type=default&display_rank=1 

Wong, S. S., & Goh, C. L. (2000). Double-blind, right/left comparison of calcipotriol ointment and betamethasone ointment in the treatment of Prurigo nodularis. Archives of dermatology, 136(6): 807–808. DOI: 10.1001/archderm.136.6.807

Zeidler, C., Tsianakas, A., Pereira, M., Ständer, H., Yosipovitch, G., & Ständer, S. (2018). Chronic Prurigo of Nodular Type: A Review. Acta dermato-venereologica, 98(2): 173–179. DOI: 10.2340/00015555-2774