Diagnosis And Treatment For Pruritus

Introduction

Pruritus is a medical term for itching whereby you have an uncomfortable sensation on your skin. The itch on your skin urges you to scratch in order to alleviate the feeling. Pruritus is a common dermatological condition that is generally not a cause for concern but could also signal an underlying medical condition. The unpleasant sensation experienced in pruritus may occur in an intermittent fashion or be persistent, either affecting a localised area of the skin or other parts of the body. Pruritus as a condition is not clearly defined or understood.1 As such, it may be quite challenging to effectively diagnose and treat the condition.

This article will take you through the concept of pruritus giving you insights into the possible causes. Here we will also discuss how pruritus is diagnosed and treated.

In-depth look at pruritus

Pruritus is an acute or chronic condition whereby the chronic form is characterised by itching that persists for more than 6 weeks.² The sensations felt in pruritus may also be difficult to resolve, debilitating the patient and compromising their quality of life. The underlying biological pathways involved in pruritus are not well understood, but a myriad of factors are implicated.³

At the physiological level, itching is caused by a variety of factors that are external and internal to the affected person. Internal factors that may trigger itching involve the endocrine system, allergies, and metabolism. The external factors may include exposure to various elements such as food, animal fur, chemicals, and a variety of other environmental factors.¹

According to the causal factor, pruritus is divided into a number of categories. Some of them are:^1,4

• Skin-derived pruritus: This type of pruritus is caused by factors that involve the skin, such as inflammation, dryness and several skin conditions
• Neuropathic pruritus: This type of pruritus is caused by sensory nerves that carry signals from the environment to the central nervous system
• Neurogenic pruritus: This type of pruritus is caused by factors involving the central nervous system
• Psychogenic pruritus: This type of pruritus is caused by psychological and psychiatric factors that affect the brain.
• Systemic pruritus.:This type of pruritus is caused by illnesses which may involve internal organs or the skin
• Mixed pruritus: This type of pruritus may involve two or more of the other types of pruritus

Pruritus may also be categorised by other factors such as the bodily area that is itching:

• Brachioradial pruritus. This type of pruritus is concerned with itching in the upper arm, outer lower arms and also the shoulders
• Nocturnal pruritus. This type of pruritus is concerned with nighttime itching which may be caused by numerous factors such as nocturnal bodily processes and irritants such as bed bugs
• Pruritus ani. This type of pruritus involves anal itching which may be caused by medical factors such as haemorrhoids⁵
• Senile pruritus. This type of pruritus is due to changes to the skin as a result of ageing. It affects people who have reached the age of 65 years⁶
• Uremic pruritus. This type of pruritus affects people with kidney disease who undergo the dialysis procedure⁷
• Pruritus also commonly occurs in pregnancy¹

Diagnosis

There are several considerations that need to be made in the diagnosis of pruritus so that the exact cause of the itching may be identified. As a starting point, the skin should be examined in order to determine whether the itch that is experienced on the skin is due to a skin condition or other causes. One way of doing this is to inspect the skin for any lesions which could signal skin disease such as a rash or inflammation. But caution is to be taken as skin lesions also arise due to scratching, which could lead to a misdiagnosis of pruritus that is caused by other factors. Skin conditions that may be signalled by itching are:³

• Eczema. In eczema, there are dry patches of skin that appear to be scaly
• Scabies. In scabies the skin is infected by the itch mite, Sarcoptes scabiei, resulting in a rash that has the appearance of pimples
• Psoriasis. This is a chronic autoimmune disease in which the skin has patches of a scaly and itchy rash that mostly appears on the scalp, elbows and knees
• Contact dermatitis. In contact dermatitis, individuals have an allergic reaction when their skin touches certain materials or objects. These include plants, jewellery and cosmetics
• Fungal infections. With fungal infections, the skin may have a rash or lumps that are discoloured
• Insect bites. People who are bitten or stung by insects may have itchy and red bumps at the site of the bite or sting
• Urticaria. This skin condition is commonly referred to as hives. With urticaria, the skin has red and itchy bumps welts
• Pityriasis rosea. This skin condition typically begins as a small oval and scaly rash on the chest, abdomen, back, thigh, upper arm or neck. This oval patch of rash is called a herald patch. After the appearance of the herald patch, the rash then spreads, and may even affect the arms and legs

In the absence of any skin abnormalities, the underlying cause of the itch requires further medical investigations. Since there are many diseases that could lead to itching, blood tests need to be carried out in order to determine the cause of the itch, especially if the itch does not respond to medications. Between 14 and 24 % of pruritus cases are due to factors that exclude the skin.⁸ The tests that could be conducted include detecting blood sugar levels in order to exclude diabetes as a causal factor for itching. Kidney and liver function tests may also be carried out in order to ensure that these organs are not affected. For patients who have a risk of contracting HIV or hepatitis C, tests could also be conducted in order to determine if they are infected.³

Treatment

There are a variety of treatments that may be administered for patients with pruritus. This is because itching is caused by a wide-ranging set of diseases. Treatment could also include non-pharmaceutical remedies. However, there are still some issues with the treatments as they are not amongst different patients. Furthermore, a previous study involving oral placebos showed that a significant proportion of pruritus patients who were treated with placebos seemed to heal. Therefore, it could be difficult to actually find out which of the medications that are indicated for pruritus actually work. In this section, we will look at the categories of treatments that are administered in patients of pruritus.^3,8

Nonpharmaceutical interventions

Skincare

Skin care is essential in the treatment and prevention of pruritus as skin dryness and damage may aggravate itching. Skin care includes applying emollients so as to prevent skin dryness and the use of mild soaps with lukewarm water. Irritants such as cleaning chemicals should also be avoided as wool. Sufferers of pruritus should also avoid washing with soap too frequently as this could dry the skin. Scratching of the itchy area could also be reduced by covering the itchy areas and keeping the fingernails trimmed.⁸

Pharmaceutical therapeutics

Topical treatment

Medications that can be applied to the skin are also used to manage pruritus.^2,3,8

• Topical corticosteroids in cases of inflammation
• Topical calcineurin inhibitors for various types of pruritus
• Topical capsaicin results in a burning effect and reduces sensitivity so as to ease the feeling of itching
• Topical menthol is thought to provide a cooling effect that decreases the itching sensation

Systemic treatment

These are some of the systemic drugs that are used to treat pruritus:^2,3,8

• Antihistamines such as hydroxyzine and diphenhydramine are used to treat pruritus that involves the histamine allergy pathway
• Opioid receptor antagonists such naloxone and nalfurafine 
• Antidepressants such as doxepin and mirtazapine have also been reported to be effective against pruritus

Other treatment strategies

These are alternative strategies which may be used to alleviate itching:^1,3

• Ultraviolet therapy has been reported to be effective in treating uremic pruritus
• Cutaneous field stimulation has been reported to effectively treat localised pruritus

Summary

Pruritus is a common dermatological symptom that is characterised by itching. In most cases, it is a self-resolving discomfort that could be relieved by scratching. However, in some cases, it points to an underlying disease. Pruritus could be limited to a small area of the skin or could be widespread. Since pruritus has many causes and the underlying biological pathways are poorly understood, the condition may be difficult to treat and diagnose. The condition is divided into various categories according to the cause of the itching. Pruritus may also be categorised according to the area of the itch. To diagnose, the first step is to determine whether the cause of the itch is due to issues of the skin or an underlying medical condition. If skin conditions have been eliminated as the source of the itching, medical diagnostic procedures must be carried out in order to determine what could be the underlying factor. The treatment of pruritus includes different types of medication as well as appropriate skin care such as a non-pharmaceutical intervention. Therapeutics for pruritus are divided into two groups, topical medications and systemic drugs. The topical medications are applied to the itchy area in order to relieve the sensations. The systemic drugs include antihistamines, opioid receptor antagonists and antidepressants which have been proven to relieve itching.