In brief

Scalp pruritus is a common and sometimes disabling symptom associate d with numerous dermatologic, neuropathic, systemic, and psychologic conditions. The diagnostic may require multidisciplinary understanding and interactions. Management of scalp pruritus includes removal of the aggravating factors and appropriate treatment of the underlying condition, with topical or systemic therapies. Psychotherapies can be considered to break the vicious circle of itching and scratching.

Introduction

Pruritus, or itch, is an unpleasant sensation that evokes a desire to scratch. It is a major and distressing acute or chronic symptom of various cutaneous and systemic diseases and one of the important generalized or localized symptoms in dermatological practice, with a prevalence from 13 to 45% in the general population. Pruritus can affect the scalp, even without any visible skin lesion. However, epidemiology data of scalp pruritus remains limited and quite complicated. This review article provides a brief description of the pathophysiology, the diagnostic and therapeutic management of scalp pruritus.

Pathophysiology

Various scalp structures and mediators could be involved in the pathophysiology of pruritus. Typically, 4 major mechanisms are described:

• Pruritoceptive: pruritus is initiated by the stimulation of the cutaneous free nerve endings by various inflammatory dermatological conditions and mediators, including histamine, serotonin, prostaglandin, acetylcholine, cytokines, opioids and neuropeptides.
• Neuropathic: pruritus occurs where the nervous system is damaged and is associated with numbness and tingling, herpes zoster, trauma and notalgia paresthetica.
• Neurogenic: pruritus is mediated by opioid and serotonin receptors, affects the central inhibitory circuits, and is associated with cholestasis and chronic kidney disease.
• Psychogenic: pruritus is associated with chronic stress or psychiatric disorders, such as depression and delusion of parasitosis. Psychological factors may influence itch perception.

The scalp microbiome could also play an important role. Fungi Malassezia species are identified as an aggravating factor in various pruritic skin conditions. Bacteria Cutibacterium species and Staphylococci could be involved in the mechanism of scalp pruritus. Impaired skin barrier function and sebum production are also observed in scalp pruritus.

Classification

Scalp pruritus can be classified according the potential underlying diseases (Table 1).

Diagnostic Approach of Scalp Pruritus

Diagnostic considers history, physical examination to determine a possible dermatologic condition or another underlying condition. Evaluation should focus on a dermatologic cause if a primary skin lesion is present. The diagnostic approach is described in Figure 1.

Figure 1. Diagnostic approach for scalp pruritus.

Management

Management of scalp pruritus relies on the diagnosis of the underlying condition if any, and the removal of the aggravating factors. Hair care practices should be performed gently by using hypoallergenic products and avoidance of chemical irritants, fragrance, and hot blow-drying. Shampoos with anti-inflammatory effects, such as zinc pyrithione, ketoconazole, seleniumsulfide, and coal tar, can be used to reduce scalp inflammation. Certain vehicles, such as ointment and cream, can be messy to apply and adhere to the hair shaft, resulting in a greasy appearance and decreased patient compliance due to cosmetic unacceptability

Topical therapy is the mainstay of treatment. A combination of topical and systemic therapy is indicated for widespread and recalcitrant diseases. Main topical therapies are glucocorticoids, calcineurin inhibitors (pimecrolimus, tacrolimus), menthol, capsaicin, polidocanol and liquor carbonis detergens. Systemic therapies are rarely indicated as first line treatment and include antihistamines, anticonvulsants, opioids, antidepressants, cyclosporin A, thalidomide Phototherapy (ultraviolet B or ultraviolet A with psoralen) can be used since it provides anti-inflammatory effect, antiproliferative effect, and mast-cell apoptosis with less adverse events. Psychotherapies, such as behavior therapy, reduce stress and increase sense of control of scratching and can be considered to break the vicious circle of itching and scratching.

Conclusion

Scalp pruritus is a common and sometimes disabling symptom of numerous dermatologic, neuropathic, systemic, and psychogenic conditions. The diagnostic and management require multidisciplinary understanding and interactions.