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Prurigo nodularis: Causes

What causes prurigo nodularis?

This disease starts with intensely itchy skin. Scratching, picking, or rubbing the intensely itchy skin causes itchy bumps and patches on the skin. It usually takes six or more weeks of frequent scratching, picking, or rubbing before the bumps and patches appear.

Black people are more likely than white people to develop prurigo nodularis

A study at Johns Hopkins Hospital found that Black patients with prurigo nodularis were also likely to have a condition like kidney disease, hepatitis C, atopic dermatitis, or depression.

Woman showing dermatologist how lupus affects her skin

Researchers are trying to understand exactly why the itchy skin develops. Many people who develop prurigo nodularis have a condition that makes their skin intensely itchy. These conditions include atopic dermatitis, an allergy, and end-stage kidney disease.

What complicates matters is the following:

  • Some people who develop prurigo nodularis do not have another condition that causes itchy skin.

  • Many people who have intensely itchy skin never get prurigo nodularis.

This makes it unclear what causes prurigo nodularis. It’s likely that no one thing causes this disease.

It’s possible that when conditions are just right inside the body, these bumps appear. What makes conditions just right may be intense inflammation inside the body, thickened (and more excitable) nerves due to scratching, and changes in the person’s immune system. More research is needed to find out.

Some people have an increased risk for prurigo nodularis

While studying this disease, researchers have learned that some people have a higher risk of developing prurigo nodularis.

This disease is more common in people who are:

  • 50 years of age or older, usually between 51 and 65 years of age

  • Black, especially if they have atopic dermatitis that flares often

  • Living with certain long-term diseases

The long-term diseases that have been linked to a higher risk of developing prurigo nodularis include:

  • Atopic dermatitis

  • Contact dermatitis

  • Diabetes

  • End-stage kidney disease

  • Hepatitis C

  • HIV that’s untreated

  • Lymphoma (Hodgkin’s lymphoma, non-Hodgkin’s lymphoma)

  • Mental health conditions, including anxiety or depression

While some people have a higher risk of getting prurigo nodularis, it’s important to know that this disease can occur at any age. If you have itchy bumps on your skin that last for more than two weeks, see a dermatologist.

If you have prurigo nodularis, an early diagnosis and treatment can relieve the itch and clear the bumps. When the itchy bumps could be a sign that you have another disease like one listed above, your dermatologist can help you get the care you need.

To find out how dermatologists diagnose and treat prurigo nodularis, go to: Prurigo nodularis: Diagnosis and treatment.

Getty Images

Boozalis E, Tang O, et al. “Ethnic differences and comorbidities of 909 prurigo nodularis patients.” J Am Acad Dermatol. 2018;79(4):714-9.

Elmariah S, Kim B, et al. “Practical approaches for diagnosis and management of prurigo nodularis: United States expert panel consensus.” J Am Acad Dermatol. 2021;84(3):747-60.

Huang AH, Williams KA, et al. “Prurigo nodularis: Epidemiology and clinical features.” J Am Acad Dermatol. 2020;83(6):1559-65.

Legat FJ, Weisshaar E, et al. “Pruritus and dysesthesia.” In: Bolognia JL, et al. Dermatology. (4th edition). Mosby Elsevier, China, 2018: 115-6.

Leis M, Fleming P, et al. “Prurigo nodularis: Review and emerging treatments.” Skin Therapy Lett. 2021;26(3):5-8.

Qureshi AA, Abate LE, et al. “A systematic review of evidence-based treatments for prurigo nodularis.” J Am Acad Dermatol. 2019;80(3):756-64.

Whang KA, Le TK, et al. “Health-related quality of life and economic burden of prurigo nodularis.” J Am Acad Dermatol. 2021;28:S0190-9622(21)01028-8.

Williams KA, Huang AH, et al. “Prurigo nodularis: Pathogenesis and management.” J Am Acad Dermatol. 2020;83(6):1567-1575.

Written by:
Paula Ludmann, MS

Reviewed by:
Shari Lipner, MD, PhD, FAAD
J. Klint Peebles, MD, FAAD
Caroline Robinson, MD, FAAD

Last updated: 9/14/21