Prurigo Nodularis

Prurigo Nodularis: A Rare Painful Skin Rash

Prurigo Nodularis: A Rare Painful Skin Rash


About Prurigo Nodularis: Painful Skin Rash 

According to Yale Medicine, Prurigo Nodularis (PN) is a rare condition characterized by firm, highly itchy bumps on the skin. It is a symmetrical painful skin rash usually affecting the arms, legs, abdomen, and upper and lower back. The nodules do not form in the palms, soles of the feet, face, or other areas that are hard to reach.  

Itching from PN usually occurs at night, and the person scratches it to the point where it bleeds. The extreme discomfort makes sleeping difficult and negatively affects mental health. Scratching can trigger nodule formation. Once the skin is scratched, new nodules keep forming in an endless itch-scratch cycle.

Prurigo nodularis is neither hereditary nor contagious. While the exact cause of this disease is unknown, it can originate from immunological and neurological abnormalities. Treatments are usually symptomatic. Multiple prurigo nodularis clinical trials are conducted to search for potential treatment options for this condition. 


Who is at Risk for Prurigo Nodularis?

Prurigo nodularis is associated with conditions that cause the skin to itch, like atopic dermatitis or insect bites. People with certain underlying conditions such as hepatitis C, HIV, heart failure, thyroid disease, lymphoma, and liver disease are at risk of developing prurigo nodularis. 


Etiology of Prurigo Nodularis

Although prurigo nodularis is rare, specific demographics and underlying conditions are more prone to it.

It is more common in people who:

  • Are of African American origin, usually between the age of 51 and 65,
  • Frequently suffer from atopic dermatitis,
  • Are females,
  • Have untreated hepatitis C,
  • Could have other infections from helicobacter pylori, strongyloides stercoralis, or mycobacteria,
  • Have long-term conditions that compromise immunity including diabetes, end-stage renal disease, or contact dermatitis, and
  • Suffer from depression and anxiety because of Hodgkin’s and non-lymphoma Hodgkin’s.


Symptoms of Prurigo Nodularis

Prurigo nodularis may initially present as a tiny red itchy nodule that can develop anywhere on the body where you scratch. 

The appearance of these bumps may vary from flesh tones to pink, brown, or black scabby warty-looking bumps that are hard, crusty, and scaly. This painful skin rash can be challenging to live with, as it makes the person repeatedly scratch it to the point of bleeding and pain. Some people even experience elevated temperatures or burning sensations in the skin. 

Here are a few additional signs encountered by people with prurigo nodularis:

  • Over time the painful skin rash may become distinctly symmetrical in appearance. 
  • Nodules have fixed sizes and shapes and do not go away on their own.
  • The quantity of nodules increases with time.
  • A common disorder in the family linked to prurigo nodularis.
  • Mental health issues due to excessive itchiness and worrying.
  • Loss of confidence.


Diagnosis of Prurigo Nodularis

Clinical testing can be used to diagnose prurigo nodularis. Prurigo nodularis patients have a long-standing history of painful skin rash, severe pruritis with skin-colored nodular lesions on the extensor surfaces of the body. Furthermore, dermoscopy can help diagnose PN. 

Your doctor may ask for a skin biopsy if they see visible bleeding and ulcerations, or when first-line therapy is of no use. In a biopsy, a small piece of skin tissue is removed using a scalpel or other device. A pathologist will examine the tissue sample under a microscope to finalize the diagnosis.

Blood tests may include complete blood cell count, metabolic panel, thyroid studies including TSH and free T4, urinalysis, stool exam, HIV antibodies, and chest x-ray. Elevated serum IgE is also evident in patients with prurigo nodularis. 


Clinical Characteristics

Each prurigo nodule:

  • is solid 
  • is 1-3 cm in diameter
  • has a raised warty surface
  • is covered by scaling and crusting
  • can be surrounded by skin that is paler or darker

Prurigo nodularis lesions are usually numerous and grouped from 2 and up to 200 at a single site. They typically begin on the lower arms and legs and get worse on the outside. Other common sites are the face, palm, and trunk. Often, these are most notable on the nape area (neck, shoulders, and upper arms).

If these lesions start to bleed, the risk of secondary infection increases. Resultantly, the lesion may become crusty, erythematous, and painful.


Causes of Prurigo Nodularis

Dietary Link to Prurigo Nodularis:

Some people term prurigo nodularis as ‘keto rash’ because it is common in people who follow a strict ketogenic diet. A ketogenic diet involves consuming a lot of fats and proteins while avoiding carbohydrates. A ketogenic diet aims to induce metabolic ketosis in which the body begins using stored fats. 

According to some research studies, alteration of the gut microbiome causes PN. The imbalance in the gut microbiome reduces immunity and makes a person more susceptible to PN.


Foods Not to Consume:

Your doctor might stop you from using a ketogenic diet, which may involve avoidance of:

  • Red meat
  • Processed foods 
  • Food that contains trans fat
  • Fried food
  • Refined sugars and flour


Also read: Prurigo Nodularis foods to avoid


Foods to Consume:

Diets high in fiber and primarily based on plant sources may help balance the imbalances caused by a ketogenic diet. These include:

  • High starch vegetables
  • Sour fruits (bananas, dates)
  • Legumes (lentils, beans)
  • Entire grains (whole-wheat bread, rolled oats, quinoa)


Moreover, anti-inflammatory foods are also incorporated. These may include:

  • Spices (cinnamon, cumin, ginger, turmeric)
  • Fish that are high in fat (salmon, herring, or mackerel) 
  • Vegetable and fruits
  • Dark chocolate
  • Green tea
  • Olive oil


Treatment of Prurigo Nodularis

It is important to take a holistic approach while treating prurigo nodularis. Patients are educated about daily care practices, given assurance, and treated for underlying psychological disorders first. In addition to these, both topical and systemic medications are given. 


Daily Care Routine:

  • Keeping nails trimmed
  • Wearing long sleeves and gloves to keep from scratching and covering the lesions
  • Use gentle skin cleaners and keep the skin moisturized 
  • Staying in a comfortable environment
  • Reduce stress in daily life 


Topical Care:

  • Calamine lotion or other lotions that contain menthol and camphor
  • Application of topical steroid
  • Injection of intraocular steroids
  • Lotions containing phenols and local anesthesia
  • Coal tar cream
  • Calcipotriol ointment
  • Capsaicin cream
  • Cryotherapy with liquid nitrogen
  • Pulsed dye laser


Systemic Treatments:

  • Antihistamines
  • Systemic corticosteroids
  • Cyclosporin, methotrexate, and azathioprine
  • Naltrexone
  • Systemic retinoids
  • Psoralen combined with ultraviolet A (PUVA)
  • Narrow Band UVB Phototherapy
  • Immunomodulatory macrolide
  • Gabapentin



Prurigo nodularis is a benign condition, so one does not have to worry about it. Although the exact cause is unknown, an underlying cause is present. Its treatment is usually multifaceted. You’ll probably benefit from a mix of topical, pharmaceutical, and healthy lifestyle changes.

Lastly, finding appropriate treatment may be difficult. The good news is that there are multiple clinical research organizations in Michigan that are working with researchers and doctors to investigate new treatments for prurigo nodularis.