June 27, 2025 | Black & Kletz Allergy
Prurigo nodularis is a chronic inflammatory skin disease where an extremely itchy rash in the form of firm bumps called nodules appears most commonly on the arms, legs, upper back, and/or abdomen. The rash is usually symmetrically distributed on both sides of the body. The itchiness, burning, and stinging sensation associated with prurigo nodularis is so severe that it often interferes with sleep and one’s psychological well-being.
The exact cause of prurigo nodularis is unknown, but altered function of the immune system and nerves in the skin is believed to be associated with heightened sensations of itchiness (i.e., pruritus) that leads to frequent scratching. Frequent scratching and picking of the skin are also thought to contribute to further lesion formation and thickening seen in the disease.
Prurigo nodularis can occur at any age but is more common in the elderly. When it occurs in younger patients, it is more likely to be associated with inflammatory skin diseases, usually eczema (i.e., atopic dermatitis). Prurogo nodularis is also more likely to manifest in patients with other underlying medical conditions that affect multiple body systems, such as cancer, diabetes, chronic kidney disease, and HIV infection. Prurigo nodularis is not hereditary or contagious.
The rash and itching can be episodic or continuous, lasting for several months in some individuals. It is typically worsened by sweat, heat, synthetic clothing, and/or stress. The rash can range in severity from just a few to several hundred lesions. The lesions can range in size from 0.2 inches to 0.8 inches wide and can appear as firm, dome-shaped papules, nodules, or plaques. Lesions can be flesh-colored, pink, red, brown, or black in color.
Diagnosis:
- The characteristic appearance and distribution of the lesions, the chronicity, and association with other systemic disorders provide clues to the diagnosis of prurigo nodularis.
- The confirmation of the diagnosis is established by biopsy of the skin lesions and examination of them under a microscope. It usually reveals thickening of different areas of the outermost layer of the skin (i.e., epidermis) with distinct changes (i.e., hyperkeratosis) to the skin protein keratin. The layer below the epidermis, referred to as the dermis, shows an increase in several inflammatory white blood cell types.
- Blood tests including a complete blood cell count (CBC), a comprehensive metabolic panel (CMP) that includes liver and kidney function tests, and a thyroid hormone panel may be beneficial for diagnosing an underlying systemic disease that may be contributing to the prurigo nodularis.
- Behavioral treatments for prurigo nodularis include ways to prevent scratching and dryness, such as keeping fingernails short, wearing long sleeves, wearing gloves, bandaging lesions, cleaning skin with gentle cleansers, keeping skin moisturized with non-irritating lotions, and avoiding warm environments to reduce sweating. Recommended anti-itch lotions include calamine, menthol, and camphor lotions.
- Moisturizers such as petroleum jelly, fragrance-free and ceramide-rich creams or ointments, and fragrance-free oatmeal or hyaluronic acid creams.
- Second generation oral antihistamines such as Zyrtec, Xyzal, Allegra, Claritin, or Clarinex taken on a regular basis. Many patients need 2 to 3 times the regular daily dose to get adequate relief from the severe itching and/or burning sensation that can be present in some individuals.
- Some patients respond better to first generation sedating antihistamines such as Palgic, Periactin, Atarax, or Benadryl.
- Topical medications such as corticosteroids (e.g., triamcinolone, fluocinonide, betamethasone, mometasone, clobetasol, fluticasone, desoxymetasone), calcineurin inhibitors (e.g., pimecrolimus, tacrolimus), capsaicin (the spicy ingredient in chili peppers), and vitamin D.
- Phototherapy: Exposing affected areas of the skin to specific wavelengths of ultraviolet (UV) light may help reduce the itchiness and inflammation of the skin.
- In 2022, dupilumab (i.e., Dupixent), an interleukin-4 receptor alpha antagonist, was approved by the U.S. Food and Drug Administration (FDA) to treat adults with prurigo nodularis. It is a subcutaneous (SQ) injection which can be self-administered under the skin every 2 weeks.
- In 2024, nemolizumab (i.e., Nemluvio), an interleukin-31 receptor antagonist, was approved by the FDA to treat adults with prurigo nodularis. It is a subcutaneous (SQ) injection administered every 4 weeks.
- Immunosuppressants such as cyclosporin, azathioprine, and methotrexate are reserved for the most resistant cases of prurigo nodularis because they affect more body systems and can have more serious side effects.
