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Am Fam Physician. 2022;105(1):55-64

Patient information: See related handout on pruritus, written by the authors of this article.

This clinical content conforms to AAFP criteria for CME.

Author disclosure: No relevant financial relationships.

Pruritus is the sensation of itching; it can be caused by dermatologic and systemic conditions. An exposure history may reveal symptom triggers. A thorough skin examination, including visualization of the finger webs, anogenital region, nails, and scalp, is essential. Primary skin lesions indicate diseased skin, and secondary lesions are reactive and result from skin manipulation, such as scratching. An initial evaluation for systemic causes may include a complete blood count with differential, creatinine and blood urea nitrogen levels, liver function tests, iron studies, fasting glucose or A1C level, and a thyroid-stimulating hormone test. Additional testing, including erythrocyte sedimentation rate, HIV screening, hepatitis serologies, and chest radiography, may also be appropriate based on the history and physical examination. In the absence of primary skin lesions, physicians should consider evaluation for malignancy in older patients with chronic generalized pruritus. General management includes trigger avoidance, liberal emollient use, limiting water exposure, and administration of oral antihistamines and topical corticosteroids. If the evaluation for multiple etiologies of pruritus is ambiguous, clinicians may consider psychogenic etiologies and consultation with a specialist.

Pruritus is the sensation of itching. Although large-scale epidemiologic data on prevalence are limited, pruritus is a common symptom encountered in primary care.1,2 The etiology of pruritus is complex and can include histamine, serotonin, and neuropeptide release, and neuronal itch signal transmission.1 Risk factors include older age, known or new dermatologic disease, and systemic conditions, such as renal and hepatic disease.1 When inadequately treated, pruritus can adversely affect a patient's quality of life by altering mood, stress levels, and sleep.3

Clinical recommendationEvidence ratingComments
Differentiate lesions as primary to pruritus or secondary (e.g., excoriations, scarring). Primary skin lesions indicate skin disease.1,5 CExpert opinion
Counsel patients with a history of irritant and allergic contact dermatitis to avoid contact irritants and other triggers (e.g., rough textiles, detergents, perfumes, chemicals, dyes).1,4,10 CProfessional society guideline based on expert opinion
The physical examination for pruritus should include a complete dermatologic assessment.1 CProfessional society guideline based on expert opinion
Consider additional skin testing (e.g., biopsy, scraping, culture) for persistent, unexplained pruritus.1,2,10 CProfessional society guideline based on expert opinion
Consider the following serologic studies when pruritus is undifferentiated after initial evaluation: complete blood count, iron studies, renal and hepatic function tests, thyroid-stimulating hormone, and fasting glucose or A1C.1,2,4,10 CProfessional society guidelines based on case-control studies and expert opinion
Encourage liberal use of emollients and limiting water exposure to reduce dry skin.1,47,48 BProfessional society guideline and multiple RCTs for treatment of atopic dermatitis
Use oral antihistamines and topical corticosteroids for initial symptomatic therapy in patients with pruritus.1,37,38,40,41 BProfessional society guideline and several small RCTs
Lifestyle modifications and cognitive behavior therapy can be considered for resistant symptoms of pruritus.1,49 BProfessional society guideline based on a Cochrane review of 10 RCTs

Differential Diagnosis

The differential diagnosis of pruritus is broad and includes acute and chronic (i.e., at least six weeks of symptoms) presentations.1,2 Primary and secondary skin lesions suggest dermatologic etiologies of pruritus (Table 14). When distinct exposures result in symptoms, the underlying etiology is often discovered. However, the absence of obvious triggers or examination findings coupled with chronic symptoms makes identifying the underlying etiology of pruritus more challenging.

EtiologyFeatures
Allergic or irritant contact dermatitisBullae, vesicles, erythema, and edema localized to area in contact with exposure
Reaction within days of exposure
Atopic dermatitisErythematous papules, patches, or plaques; pruritic area where rash appears when scratched in patients with atopic conditions (e.g., allergic rhinitis, asthma)
Involvement of crease areas (axillae, wrists, ankles, popliteal and antecubital fossae)
Chronic, worsens with itch-scratch cycle
Bullous pemphigoidInitially pruritic urticarial lesions, often in intertriginous areas
Formation of tense blisters
Cutaneous T-cell lymphoma (mycosis fungoides)Oval eczematous patch on skin with no sun exposure (e.g., buttocks)
Possible presentation of new eczematous dermatitis in older adults
Possible presentation of erythroderma
Dermatitis herpetiformisRare vesicular dermatitis affecting the lumbosacral spine, elbows, or knees
Dermatophyte infectionCan occur on several sites, including the feet, trunk, groin, scalp, and nails
Localized pruritus and rash characterized by peripheral scaling and central clearing
Patchy alopecia on scalp
Dystrophic or discolored nails
FolliculitisPruritus out of proportion to appearance of dermatitis
Papules and pustules at follicular sites on chest, back, or thigh
Lichen planusLesions often located on the flexor wrists
Characterized by the six P's (pruritus, polygonal, planar, purple, papules, plaques)
Lichen simplex chronicusLocalized, intense pruritus
Initial erythematous, well-defined plaques with excoriations lead to thickened, lichenified, violaceous patches if scratching continues
Pediculosis (lice infestation)Adult organisms and nits on hair shafts
Occiput in school-aged children; genitalia in adults (sexually transmitted)
PsoriasisPlaques on extensor extremities, low back, palms, soles, and scalp
ScabiesBurrows, vesicles, and papules in finger web spaces and axillae and on wrists, ankles, genitals, and extensor surfaces
Pruritus worse at night
Can persist after mite eradication
SunburnPossible photosensitizing cause (e.g., with use of nonsteroidal anti-inflammatory drugs or cosmetics)
Urticaria (hives)Intensely pruritic, well-circumscribed, erythematous, and elevated wheals
Lesions are transient, may coalesce, and wax and wane over several hours
XerosisIntense pruritus, often during winter months in northern climates
Involvement of back, flank, abdomen, waist, and lower extremities
More common in older people

The International Forum for the Study of Itch has proposed a formal classification system for chronic pruritus with three different clinical classes: pruritus on diseased skin (Group I), pruritus on nondiseased skin (Group II), and chronic reactive lesions acquired from skin manipulation, such as rubbing, picking, or scratching (Group III).5 Group I presentations suggest a dermatologic etiology. Group II presentations suggest systemic, neurogenic, or psychogenic etiologies. Group III presentations may result from any one of the previously mentioned etiologies or a mixed presentation. The classification also includes chronic pruritus of unknown origin, for which there are no known effective interventions.6 Pathognomonic skin findings and the extent of bodily involvement can also suggest certain diagnoses (Figure 17).

Common Dermatologic Etiologies of Pruritus

ATOPIC DERMATITIS

Atopic dermatitis is an inflammatory skin condition that is often associated with secondary lesions that result from scratching or other skin manipulation findings, such as excoriations, lichenification, and hyperpigmented or erythematous papules or plaques (Figure 2). Patients scratch pruritic areas and subsequently develop secondary lesions, worsening dermatitis and associated pruritus; this process is often called the itch-scratch cycle. Flexural areas are commonly affected, including ankles, regions behind the ears, and the antecubital and popliteal fossae. Patients with this condition often have a personal or family history of asthma or allergic rhinitis, and symptoms commonly begin during childhood. Treatment includes limiting exposure to water, liberal emollient use, and topical corticosteroid application.8,9

CONTACT DERMATITIS

Contact dermatitis is an inflammatory reaction that typically erupts within days of direct skin contact with an environmental trigger. Associated primary skin findings include bullae, vesicles, erythema, and edema, localized to areas that directly contacted the trigger. Irritant and allergic mechanisms are common. Irritant contact dermatitis is not immunologically mediated and progressively compromises the physical and chemical composition of the epidermis. In contrast, allergic contact dermatitis is dependent on a delayed hypersensitivity reaction and is more common in people with atopy. Contact dermatitis treatment includes avoidance of triggers, such as rough textiles, detergents, perfumes, chemicals, and dyes,1,4,10 and topical corticosteroid application.11

DERMATOPHYTOSIS

Tinea infections are caused by fungi that can survive only on dead keratin, including the most superficial layer of the epidermis (i.e., stratum corneum), hair, and nails. The characteristic ringworm rash appears as a well-demarcated region with a red, scaly, elevated border containing the highest concentration of fungal hyphae. Tinea pedis more often affects toe webs and soles of the feet, and the skin can become dry, scaly, fissured, or soft and macerated. Tinea capitis may present with patchy alopecia and scaling of the scalp. Onychomycosis is associated with dystrophic, discolored nails. Direct visualization of fungal hyphae on scale scrapings, hair shafts, and nail clippings prepared with potassium hydroxide solution aids in the diagnosis. Treatment includes topical and oral antifungals.12

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