Pruritus

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Introduction

Pruritus, the medical term for itching, is a sensation that provokes the desire to scratch. It is a common symptom experienced by people of all ages and can range from mild and intermittent to severe and persistent, significantly impacting quality of life. While occasional itching is usually harmless, persistent or severe pruritus can be a sign of an underlying medical condition. 

What is Pruritus?

Pruritus is defined as an unpleasant sensation on the skin that elicits the urge to scratch. It is not a disease in itself but rather a symptom that can arise from a wide array of underlying conditions affecting the skin or other bodily systems. The intensity and location of pruritus can vary greatly. It can be localised to a specific area, such as a limb or the scalp, or it can be generalised, affecting the entire body. 

 

The duration of pruritus can also vary, from acute, lasting for a short period, to chronic, persisting for six weeks or longer. Chronic pruritus can be particularly bothersome, interfering with sleep, concentration, and overall well-being. 

 

The mechanisms that cause the sensation of itch are still being actively researched, but it is known to involve specific nerve fibres in the skin that transmit signals to the brain, distinct from those that transmit pain.

Prevalence

Studies estimate that the lifetime prevalence of chronic pruritus (lasting more than six weeks) ranges from 8% to 16% in the adult population globally. The prevalence tends to increase with age. Acute pruritus is even more widespread, affecting a significant portion of the population at some point in their lives, often due to transient skin irritations or insect bites.

Types of Pruritus

Pruritus can be classified based on several factors:

Underlying Cause: This is the most clinically relevant classification:

  • Pruritoceptive Pruritus: Originates in the skin due to stimulation of itch-specific nerve fibres by various pruritogens (itch-inducing substances) such as histamine, proteases, and neuropeptides. Common causes include skin conditions like eczema, psoriasis, urticaria, and insect bites.
  • Neuropathic Pruritus: Results from damage or dysfunction of the peripheral or central nervous system. Examples include postherpetic neuralgia, multiple sclerosis, and nerve compression. The itch sensation is often described as burning, tingling, or stabbing.
  • Psychogenic Pruritus: Is believed to be related to psychological factors such as stress, anxiety, and depression. The itch may not have a clear dermatological or systemic cause.
  • Systemic Pruritus: Arises from underlying systemic diseases that release pruritogenic mediators or affect neural pathways involved in itch. Examples include liver disease (cholestatic pruritus), kidney disease (uraemic pruritus), haematological disorders (polycythaemia vera, Hodgkin lymphoma), and endocrine disorders (hyperthyroidism).
  • Mixed Pruritus: In some cases, pruritus may have multiple contributing factors, making it difficult to classify into a single category.

 

Distribution:

  • Generalised Pruritus: Itch affecting the entire body. This is often associated with systemic diseases or certain skin conditions.
  • Localised Pruritus: Itch confined to a specific area of the body, such as the scalp (scalp pruritus), anus (pruritus ani), or vulva (pruritus vulvae). Localised pruritus is often due to local skin conditions or irritants.

 

Duration:

  • Acute Pruritus: Itch that lasts for a short period (less than six weeks), often related to a temporary skin irritation or allergic reaction.
  • Chronic Pruritus: Persistent itch lasting for six weeks or longer. This can be more challenging to manage and significantly impacts quality of life.

Causes of Pruritus

The causes of pruritus are diverse and can be broadly categorised as dermatological, systemic, neurological, and psychogenic:

Dermatological Causes (Skin Conditions):

  • Eczema (Atopic Dermatitis): A chronic inflammatory skin condition characterised by itchy, red, dry, and cracked skin.
  • Psoriasis: An autoimmune condition that causes scaly, itchy patches on the skin.
  • Urticaria (Hives): An allergic reaction causing raised, itchy welts on the skin.
  • Contact Dermatitis: Inflammation of the skin caused by direct contact with an irritant (e.g., soaps, detergents, chemicals) or an allergen (e.g., poison ivy, nickel).
  • Dry Skin (Xerosis): A common condition, especially in older adults and during winter, where the skin lacks sufficient moisture, leading to itching.
  • Scabies: An infestation of the skin by tiny mites that burrow into the skin, causing intense itching, particularly at night.
  • Lichen Planus: An inflammatory condition that can affect the skin, mouth, nails, and genitals, often causing itchy, purplish bumps.
  • Fungal Infections (e.g., Tinea): Ringworm and other fungal infections can cause localised itching.
  • Insect Bites and Stings: Reactions to insect saliva or venom can cause localised itching and inflammation.

 

Systemic Causes (Underlying Medical Conditions):

  • Liver Disease (Cholestatic Pruritus): Impaired bile flow can lead to a build-up of bile salts in the skin, causing intense itching.
  • Kidney Disease (Uraemic Pruritus): The accumulation of waste products in the blood due to kidney failure can cause widespread itching.
  • Haematological Disorders: Conditions like polycythaemia vera (increased red blood cells) and Hodgkin lymphoma (cancer of the lymphatic system) can be associated with pruritus.
  • Endocrine Disorders: Hyperthyroidism (overactive thyroid gland) and diabetes mellitus can sometimes cause itching.
  • Iron Deficiency Anaemia: Low iron levels can occasionally lead to pruritus.
  • Malignancies: Certain cancers, such as leukaemia and myeloma, can be associated with itching.
  • HIV Infection: Pruritus can be a symptom of HIV infection.

 

Neurological Causes (Nerve-Related Issues):

  • Postherpetic Neuralgia: Persistent nerve pain and itching following a shingles outbreak.
  • Multiple Sclerosis: A chronic disease affecting the central nervous system that can cause neuropathic itching.
  • Nerve Compression or Entrapment: Pressure on nerves can sometimes lead to localised itching.
  • Brachioradial Pruritus: An intense itching sensation in the forearms, possibly related to nerve compression in the neck or sun exposure.

 

Psychogenic Causes (Psychological Factors):

  • Stress, Anxiety, and Depression: Emotional distress can sometimes manifest as itching without a clear physical cause.
  • Obsessive-Compulsive Disorder: Some individuals may experience compulsive scratching as a manifestation of OCD.

 

Other Causes:

  • Pregnancy (Pruritus Gravidarum): Hormonal changes during pregnancy can sometimes cause itching.
  • Medications: Certain drugs, such as opioids, aspirin, and some blood pressure medications, can have pruritus as a side effect.
  • Age (Senile Pruritus): Dry skin, common in older adults, is a frequent cause of itching.

Symptoms of Pruritus

  • Persistent Itching: A continuous urge to scratch
  • Skin Lesions: Redness, bumps, or blisters resulting from scratching.
  • Dry or Scaly Skin: Especially in chronic cases.
  • Sleep Disturbances: Itching worsening at night, leading to insomnia.
  • Emotional Distress: Anxiety or depression due to persistent discomfort.

Diagnosis of Pruritus

Diagnosing the underlying cause of pruritus can be challenging and often requires a thorough evaluation:

  • Medical History: The doctor will ask detailed questions about the onset, duration, location, intensity, and quality of the itching, as well as any associated symptoms, past medical history, medications, allergies, and family history of skin conditions or systemic diseases.
  • Physical Examination: A thorough examination of the skin is crucial to identify any visible skin lesions or signs of underlying dermatological conditions. The distribution and appearance of any skin changes can provide clues to the cause of the pruritus.
  • Blood Tests: Depending on the clinical suspicion, various blood tests may be ordered to screen for systemic diseases such as liver disease (liver function tests), kidney disease (renal function tests), thyroid disorders (thyroid function tests), blood disorders (complete blood count), and iron deficiency (ferritin levels).
  • Skin Biopsy: If a skin condition is suspected, a small skin sample may be taken and examined under a microscope to aid in diagnosis.
  • Allergy Testing: If allergic contact dermatitis or urticaria is suspected, patch testing or skin prick testing may be performed to identify specific allergens.
  • Imaging Studies: In some cases, imaging tests such as chest X-rays or abdominal ultrasounds may be necessary to investigate underlying systemic diseases.
  • Neurological Examination: If neuropathic pruritus is suspected, a neurological examination may be performed to assess for nerve damage or dysfunction.
  • Psychiatric Evaluation: If psychogenic pruritus is suspected, a psychiatric evaluation may be helpful to identify any underlying psychological factors.
  • Pruritus Diary: Keeping a diary to track the timing, location, intensity, and triggers of the itching can provide valuable information for diagnosis and management.

Treatment of Pruritus

The primary goal of pruritus treatment is to identify and address the underlying cause whenever possible. Symptomatic relief is also crucial to improve the patient's comfort and quality of life. Treatment strategies may include:

Treating the Underlying Cause: 

If the pruritus is due to a skin condition (e.g., eczema, psoriasis, scabies), systemic disease (e.g., liver disease, kidney disease), or medication side effect, treating the primary condition or discontinuing the offending drug is essential.
 

Topical Treatments:

  • Emollients (Moisturisers): Regular use of fragrance-free and hypoallergenic emollients helps to hydrate the skin and relieve itching caused by dryness.
  • Topical Corticosteroids: These anti-inflammatory creams and ointments can be effective for reducing itching associated with inflammatory skin conditions like eczema and dermatitis. The potency and duration of use should be guided by a doctor.
  • Topical Calcineurin Inhibitors (e.g., Tacrolimus, Pimecrolimus): These non-steroidal anti-inflammatory creams can be used for eczema and other inflammatory skin conditions, particularly in areas where topical corticosteroids may have side effects.
  • Topical Antihistamines (e.g., Doxepin Cream): These can provide localised relief from itching, but systemic antihistamines are often more effective for widespread pruritus.
  • Topical Local Anaesthetics (e.g., Pramoxine): These can provide temporary relief from itching by numbing the skin.
  • Capsaicin Cream: May be helpful for neuropathic pruritus in some cases, although it can initially cause a burning sensation.

 

Systemic Medications:

  • Antihistamines (H1 Receptor Antagonists): These are commonly used to treat itching caused by histamine release, such as in urticaria and allergic reactions. Sedating antihistamines (e.g., chlorphenamine, hydroxyzine) (Brand available: Atarax) can be particularly helpful for nocturnal pruritus, while non-sedating antihistamines (e.g., loratadine, cetirizine) are preferred for daytime use.
  • H2 Receptor Antagonists (e.g., Ranitidine, Cimetidine): These may be used in combination with H1 antihistamines for urticaria and some other types of pruritus.
  • Gabapentin and Pregabalin: These anticonvulsant medications can be effective for neuropathic pruritus.
  • Selective Serotonin Reuptake Inhibitors (SSRIs) and Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs): These antidepressants can sometimes help with chronic pruritus, particularly if there is an underlying psychological component or neuropathic pain.
  • Ursodeoxycholic Acid: May be used to treat cholestatic pruritus associated with liver disease.
  • Naltrexone: An opioid antagonist that can sometimes be effective for cholestatic and uraemic pruritus.
  • Corticosteroids (Oral): Systemic corticosteroids may be used for severe inflammatory skin conditions or systemic diseases causing intractable pruritus, but long-term use is generally avoided due to potential side effects.
  • Immunosuppressants (e.g., Azathioprine, Cyclosporine): May be used for severe inflammatory skin conditions causing pruritus that are unresponsive to other treatments.
  • Dupilumab: A biologic medication used for severe atopic dermatitis with significant pruritus.

 

Phototherapy (Light Therapy): 

Ultraviolet B (UVB) phototherapy can be helpful for pruritus associated with certain skin conditions like psoriasis and eczema.
 

Other Measures:

  • Cooling Measures: Applying cool compresses or taking cool baths can help to soothe itchy skin.
  • Avoiding Irritants: Identifying and avoiding substances that irritate the skin (e.g., harsh soaps, fragrances, tight clothing) is important.
  • Stress Management Techniques: Relaxation exercises, meditation, and yoga may help to reduce stress-related pruritus.

Risk Factors

  • Age: Elderly individuals are more prone due to skin changes.
  • Chronic Diseases: Such as diabetes or kidney disease.
  • Environmental Factors: Dry climates or exposure to irritants.
  • Medications: Certain drugs can induce pruritus.
  • Psychological Stress: Can exacerbate symptoms.

Complications

  • Skin Infections: Due to excessive scratching.
  • Sleep Disturbances: Leading to fatigue and reduced quality of life.
  • Emotional Distress: Anxiety or depression.
  • Chronic Skin Changes: Thickening or pigmentation changes

Tips to Live with Pruritus

  • Moisturise Frequently: Apply emollients several times a day, especially after washing.
  • Keep Nails Short and Smooth: This can minimise skin damage if you do scratch.
  • Wear Cotton Gloves at Night: This can help prevent scratching during sleep.
  • Distraction Techniques: Engage in activities that take your mind off the itching, such as reading, hobbies, or socialising.
  • Relaxation Techniques: Practice relaxation exercises, meditation, or deep breathing to reduce stress and anxiety, which can exacerbate itching.
  • Identify and Avoid Triggers: Pay attention to factors that seem to worsen your itching (e.g., certain foods, fabrics, stress) and try to avoid them.

Common Misconceptions About This Condition

"It's Just Dry Skin."

While dryness can cause itch, pruritus can stem from various underlying conditions.
 

"Scratching Helps."

Scratching provides temporary relief but can worsen the condition.
 

"Only Skin Diseases Cause Itch."

Systemic diseases can also manifest as pruritus.

When to See a Doctor

It's important to see a doctor for pruritus in the following situations:

  • The itching is severe or persistent (lasting more than a few weeks).
  • The itching interferes with your sleep or daily activities.
  • The itching is accompanied by other symptoms such as fatigue, weight loss, fever, jaundice, or changes in bowel or bladder habits.
  • You develop a widespread rash or other significant skin changes along with the itching.
  • Home remedies and over-the-counter treatments do not provide relief.
  • You suspect the itching may be a side effect of a medication.
  • You have an underlying medical condition that may be contributing to the itching.

Questions to Ask Your Doctor

When you see your doctor about pruritus, consider asking the following questions:

  • What do you think is causing my itching?
  • Are there any tests you need to run to determine the cause?
  • What are the treatment options for my pruritus?
  • Are there any topical or oral medications you recommend? What skin care routine should I follow?
  • Are there any specific products I should use or avoid?
  • What can I do to relieve the itching at home?
  • How long will it take for the itching to go away?

Conclusion

Pruritus, or itchy skin, is a common and often bothersome symptom with a wide range of potential causes. While occasional itching is usually benign, persistent or severe pruritus can significantly impact quality of life and may indicate an underlying medical condition. Thorough evaluation by a healthcare professional is crucial for accurate diagnosis and appropriate management. 

FAQs

Can stress cause itching?

Yes, stress and anxiety can trigger or worsen pruritus in some individuals (psychogenic pruritus).

Is there a cure for chronic pruritus?

The possibility of a cure depends on the underlying cause. If the cause can be identified and treated effectively, the pruritus may resolve. However, for some chronic conditions, management focuses on symptom relief.

Why is my itching worse at night?

Several factors can contribute to nocturnal pruritus, including increased skin temperature, reduced distraction, and changes in the levels of certain inflammatory mediators.

Are there any foods that can make itching worse?

Certain foods can trigger allergic reactions or histamine release in some individuals, potentially exacerbating itching. Common culprits include shellfish, nuts, and strawberries. Keeping a food diary may help identify any specific triggers.

Can children experience pruritus?

Yes, children can experience pruritus due to various causes, including eczema, allergies, infections (e.g., chickenpox, scabies), and dry skin.
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