Pruritus (itch) can severely sap the quality of life. It can also further complicate the lives of people with chronic illnesses and could impact mortality. The aetiology and treatment of chronic itch are discussed in the article.

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The chronic itch can either be a symptom of a disease or a precursor of a serious illness. Unfortunately, antihistamines often do little to soothe its symptoms. Knowledge of its potential causes may help clinicians determine how to best treat patients with chronic itch.

Understanding chronic itch

Chronic itch refers to an itch that lasts 6 or more weeks. The aetiology and frequency of chronic itch vary based on age, comorbidities, climate, presence of atopy, and access to healthcare. Other potential contributing factors include living conditions, migration, and rituals. The prevalence of itch varies widely.

Itch accounts for about 1% of total US office visits per year. Despite pruritus being common, there are scant data on its duration and severity or its frequency in patients desiring medical treatment.

Despite the presence of guidelines, experts cite research that suggests about 50% of patients don’t understand why they itch. No strong associations between pruritus and age, sex, geography, or socioeconomic status have been established.

Men and women differ in what they think is most pressing regarding itch, as well as itch location, quality, and scratching behaviours. Moreover, chronic pruritus tends to affect Asian/Pacific Islanders more than other ethnic groups.

Chronic itch interferes with sleep and mediates mood disturbance/depression. For instance, the itch is considered one of the most distressing symptoms of psoriasis, with more than 75% of patients experiencing it. In patients on hemodialysis, those who experienced itch exhibited a 15% increase in death rates compared with patients who did not; this could be due to sleep issues.

Results of a survey of US dermatologists published in Itch indicated that 4.8% of patients struggled with pruritus. This estimate may be on the low side, considering that 67.9% of dermatologists excluded chronic itch secondary to psoriasis, and 44,8% excluded chronic itch secondary to atopic dermatitis.

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Chronic itch causes

Etiologies of chronic itch include dermatologic, infections, neuropathic, system, and psychiatric factors. The following are specific causes cited in the Frontiers in Medicine article:

• Malignant or systemic disease
• Xerosis cutis (ie, dry skin)
• End-stage renal disease (ie, patients on hemodialysis)
• Atopic dermatitis
• Chronic urticaria
• Psoriasis
• Drug interactions (eg, opioids, antineoplastic drugs, antimalarials)
• Infections (eg, HIV/AIDS)

Psychogenic itch is often proposed as a diagnosis. This particular diagnosis, however, must be approached gingerly, according to the authors of an article published in Translational Psychiatry.

Various aspects of psychogenic itch are contentious, including physiopathology, psychopathology, and classification. The differential diagnosis of the psychogenic itch is challenging. Looking forward, brain imaging may help better elucidate psychogenic itch.

“Psychogenic itch is a diagnosis that is (too) frequently proposed by physicians, but patients diagnosed with psychogenic itch are (too) rarely referred to psychiatrists.”

— Misery, et al.

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Treating chronic itch

According to survey data published in Itch, 77.5% of dermatologists prescribed antihistamines as first-line therapy for the severe itch, while 76.1% prescribed corticosteroids. Overall, 36.3% of patients did not get relief with available therapeutic options.

Histamine-independent pathways could contribute to chronic pruritus, which explains why antihistamines are ineffective in many patients. In these cases, biologics or κ-opioid receptor (KOR) agonists may help. These drugs, however, are expensive and require pre-authorisation if approved.

Adverse effects are another issue with newer antipruritic treatments. KOR agonists can impact the central nervous system. JAK inhibitors are immunomodulators that are also indicated for the itch, but they may cause adverse effects such as infection.

Other options to treat itch include antidepressants, antibiotics, cyclosporine, herbal medicines, antineuralgics, botulinum toxin type A, acupuncture therapy, and phototherapy.

It’s extremely important to understand the underlying trigger associated with the itch and try to treat this underlying trigger, rather than “treating the itch.” The itch is most likely a symptom of an underlying disorder, and it may be wise to consult dermatology if the itch does not resolve or improve.

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Drug-induced itch

In cases of drug-induced itch, as well as other adverse events secondary to targeted anticancer agents like epidermal growth factor receptor inhibitors, dosage reduction can interfere with the efficacy of treatment. Consequently, decreases in dosages (or flat-out discontinuation) are inadvisable.

Specialists do reduce dosages when patients complain about a disturbance in quality of life. Instead of decreasing drug dosages, antipruritic therapies are necessary, according to the authors of an article published in Current Problems in Dermatology.

“The medical care of patients with chronic pruritus may be challenging in terms of the diagnosis and therapy of the underlying diseases,” wrote the authors of the review published in Itch.

“To minimise this challenge, dermatologists may need to employ an interdisciplinary approach with specific antipruritic therapy and the collaboration of an itch specialist or centre.”

— Sedlack, et al.

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Disclaimer: This story is contributed by Naveed Saleh and is a part of our Global Content Initiative, where we feature selected stories from our Global network which we believe would be most useful and informative to our doctor members.