What Is Prurigo Nodularis? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Prurigo nodularis (PN) is a chronic inflammatory skin condition that causes firm, extremely itchy, and often painful bumps (nodules) on the surface of the skin. PN often starts with very itchy skin that can be limited to a few areas or widespread, according to the American Academy of Dermatology (AAD).

The itch is so intense that it causes an uncontrollable urge to scratch and rub, which causes more itching and inflammation. After about six weeks, hard (not pus-filled) nodules appear where the scratching has occurred.

Many (but not all) people who develop prurigo nodularis already have another skin condition that causes itchy skin, says Steven Feldman, MD, PhD, a researcher and dermatologist at Atrium Health Wake Forest Baptist in Winston Salem, North Carolina.

“For example, if you have eczema or psoriasis and you rub and scratch enough, you can develop prurigo nodules,” says Dr. Feldman. Even scratching at insect bites can cause prurigo nodules to form, he says.

The first symptom of prurigo nodularis is usually itchy skin, with some people also reporting a feeling of burning or stinging, according to AAD. The itchiness can be present most of the time or come in short bursts.

Rubbing, scratching, or picking at the skin can lead to the eventual formation of itchy, hard bumps, says Feldman. The bumps usually develop in places that are easy to scratch, per Yale Medicine, and include:

• Arms and legs
• Abdomen
• Upper and lower back

These nodules can range in size from a few millimeters to 3 centimeters and may be red, brown, black, or the same color as the rest of the skin.

The exact cause of PN is unknown, but changes in the function of the immune system and the nerves in the skin may be associated with heightened sensations of itchiness that trigger frequent scratching, according to the National Organization for Rare Disorders (NORD).

Researchers have identified certain risk factors for prurigo nodularis, including:

Age: PN is more common in people age 50 or older, usually between 51 and 65 years of age, according to the AAD.

Skin conditions: Individuals with a history of atopic dermatitis, psoriasis, or other skin conditions are more likely to develop prurigo nodularis says Feldman.

Certain underlying diseases: People with kidney failure, HIV, hepatitis C infection, certain bacterial and parasitic infections, thyroid disease, lymphoma, or liver disease may be more likely to develop prurigo nodularis, according to Yale Medicine.

Race or ethnicity: Black individuals, especially those with atopic dermatitis that flares often, are at higher risk for having prurigo nodularis, says the AAD.

Dermatologists can often diagnose prurigo nodularis by examining bumps on the skin, says Feldman, giving careful scrutiny to those in areas that can be scratched or rubbed.

If you have more than one skin condition, a dermatologist may need to perform a skin biopsy to confirm the diagnosis. The biopsy involves taking a small sample of skin tissue from a nodule and examining it under a microscope to look for specific changes in the skin cells and tissues.

Sometimes people with PN have another disease, such as diabetes, hepatitis C, and untreated HIV, so blood tests may also be part of a diagnostic work-up.

There is no cure for prurigo nodularis, but several treatments can help break the itch-scratch-itch cycle, says Feldman. These include:

• Corticosteroids: If there are just a few nodules, steroid creams or ointments can help reduce inflammation and itching, says Feldman. Oral or injectable corticosteroids may be used for more severe PN, according to Yale Medicine.
• Antihistamines: These medications can help reduce itching.
• Phototherapy: Exposure to ultraviolet (UV) light can help reduce inflammation and itching, says Feldman.
• Cryosurgery: This method, which uses extreme cold to destroy abnormal tissue, is an option if other treatments don’t help with itch and pain. But it’s often not a first or second choice in people with darker skin because it can cause noticeable light spots, scarring, or both.
• Immunomodulatory drugs: In more severe cases or when nodules don’t respond to other therapies, dermatologists may prescribe immunosuppressive drugs like methotrexate or cyclosporin to try to control inflammation, says Feldman. But these medications have negative health consequences in the long term, he adds.
• Other medications: Some dermatologists may prescribe oral naltrexone, antidepressants, gabapentin, or pregabalin.

Dupixent (dupilumab) injection is the first treatment approved by the U.S. Food and Drug Administration (FDA) for prurigo nodularis. “Dupilumab is highly effective; it’s already been approved for atopic dermatitis,” says Feldman.

Dupixent is administered via subcutaneous injection: a 300 milligram dose administered via pre-filled syringe or pre-filled pen every two weeks after an initial loading dose. In clinical trials, the drug resulted in significant improvements in itch and in reducing/clearing of nodules, per the FDA.

Lifestyle Changes and Complementary Therapies

Although it is very difficult, try to avoid scratching nodules, says Feldman. “If you just have a few spots, placing a Band-Aid over them can help,” he says.

Other tips to help with the itch-scratch cycle, from Yale Medicine:

• Use mild soaps or even no soap at all when bathing.
• Apply moisturizer several times a day.
• Spread on over-the-counter lotions and ointments to calm skin and reduce itchiness including capsaicin cream, pramoxine hydrochloride (a topical anesthetic), and products that contain camphor, menthol, and phenol.
• Keep fingernails trimmed.
• Wear gloves or mittens while sleeping to avoid unintentional scratching.

Although the findings need to be confirmed in larger studies, a case study published in November 2021 in Clinical, Cosmetic and Investigational Dermatology found that four months of acupuncture treatment significantly decreased itch and improved sleep.

Prevention of Prurigo Nodularis

Because the root cause of PN is often unknown and it’s not clear why some people get it and others don’t, there’s no tried-and-true way to prevent it.

But there are ways to prevent the itch-scratch cycle from starting, according to the AAD. Avoiding common triggers including stress, heat, humidity, sweating, dryness, scented personal care products, and clothing made of wool, polyester, or any rough fabric may help minimize symptoms.

Infection Although it isn’t common, scratching or rubbing nodules can cause infections. Swelling, discoloration, a warm or hot feeling, pus leaking from open skin, pain, or a fever can all be signs of an infection.

Call your dermatologist or primary care doctor right away if you develop any signs of an infection.

Scarring When medication or self-care measures improve prurigo nodularis itch, the nodules gradually heal but can leave scars in people with both lighter and darker skin, notes an article in the journal JAMA Dermatology.

Prurigo nodularis is relatively rare, affecting almost 88,000 people in the United States, according to NORD. People of any age can get PN, but it’s more common in those between the ages of 40 and 69 years old. Approximately 55 percent of people who get PN are women, and 45 percent are men.

PN is 3.4 times more common in Black Americans, says NORD. Black people with PN often have firmer, larger, and darker bumps that tend to leave dark spots that can take many months to years to fade, according to JAMA Dermatology.

Skin Diseases Often called eczema, atopic dermatitis is a chronic condition caused by an overactive immune system that causes skin to become discolored, itchy, and inflamed. About half of all people with PN have a history of atopic dermatitis, according to a study in the Journal of the European Academy of Dermatology and Venereology.

Other Chronic Diseases There is a link between prurigo nodularis and different medical conditions, including kidney failure, HIV, hepatitis C infection, certain bacterial and parasitic infections, thyroid disease, lymphoma, and liver disease. Some people with PN may also have diabetes.

Anxiety and Depression Prurigo nodularis is associated with a number of mental health issues. One study in the Journal of Clinical and Aesthetic Dermatology found that almost half of those with PN experienced some form of mental health problem, with anxiety and depression disorders the most common.

Prurigo nodularis can cause significant discomfort and emotional distress that have a negative impact on qualify of life, says Feldman. People with PN may have trouble sleeping and may struggle with self-confidence; they might avoid social situations, and miss work and school. They may also struggle with mental health issues.

Because of PN’s emotional and mental toll, the AAD recommends that people with PN seek out help from a mental-health professional, according to the AAD.