Some Causes of Pruritus

Atopic dermatitis

Presence of erythema, possible lichenification, keratosis pilaris, xerosis, Dennie-Morgan lines, hyperlinear palms

Usually a family history of atopy or chronic recurring dermatitis

History and physical examination

Sometimes skin biopsy

Contact dermatitis

Dermatitis secondary to contact with allergen; erythema, vesicles

History and physical examination

Sometimes patch testing

Dermatophytosis (eg, tinea capitis, tinea corporis, tinea cruris, tinea pedis)

Localized pruritus, circular lesions with raised scaly borders, areas of alopecia

Common sites are genital area and feet in adults; scalp and body in children

Sometimes, predisposing factors (eg, moisture, obesity)

KOH examination of lesion scrapings

Wood lamp examination

Lichen simplex chronicus

Areas of skin thickening secondary to repetitive scratching

Lesions are discrete, erythematous, scaly plaques, well-circumscribed, rough, lichenified skin

History and physical examination

Sometimes skin biopsy

Pediculosis

Common sites are scalp, axillae, waist, and pubic area

Areas of excoriation, possible punctate lesions from fresh bites, possible bilateral blepharitis

Visualization of eggs (nits) and sometimes lice

Psoriasis

Plaques with silvery scale typically on extensor surfaces of elbow, knees, scalp, and trunk

Pruritus not necessarily limited to plaques

Possibly small-joint arthritis manifesting as stiffness and pain

History and physical examination

Sometimes skin biopsy

Scabies

Small erythematous or dark papules at one end of a fine, wavy, slightly scaly line up to 1 cm long (also called burrows); possibly on web spaces, belt line, flexor surfaces, and areolas of women and genitals of men

Family or close community members with similar symptoms

Intense nocturnal pruritus

History and physical examination

Microscopic examination of skin scrapings from burrows

Urticaria

Evanescent, circumscribed, raised, erythematous lesions with central pallor

Can be acute (< 6 weeks) or chronic (≥ 6 weeks)

History and physical examination

Sometimes additional testing (eg, thyroid function tests, tests for autoimmune disorders, basophil activation tests)

Xerosis (dry skin)

Most common in the winter

Pruritic, dry, scaly skin, mostly on lower extremities

Exacerbated by dry heat

History and physical examination

Allergic reaction, internal (numerous ingested substances)

Generalized pruritus, rash with macules and papules or urticarial rash

May or may not have known allergy

Trial of avoidance

Sometimes allergy (skin-prick) testing

Cancer (eg, Hodgkin lymphoma, polycythemia vera, mycosis fungoides)

Cancer-associated paraneoplastic syndromes

Pruritus may precede any other symptoms

Burning quality to pruritus, primarily in lower extremities (Hodgkin lymphoma)

Pruritus after bathing (polycythemia vera)

Heterogeneous cutaneous lesions—plaques, patches, tumors, erythroderma (mycosis fungoides)

Intense oral erosions, crusting, and tense blisters (paraneoplastic pemphigus)

Concentric erythematous lesions (erythema gyratum repens)

Complete blood count and bone marrow biopsy for polycythemia vera

Lymph node or bone marrow biopsy for Hodgkin lymphoma

Skin biopsy for mycosis fungoides

Cholestasis

Findings suggestive of liver or gallbladder damage or dysfunction (eg, jaundice, steatorrhea, fatigue, right upper quadrant pain)

Usually widespread pruritus without rash, developing sometimes in late pregnancy

Tests for cholestasis

Diabetes*

Urinary frequency, thirst, weight loss, vision changes

Urine and blood glucose

HbA1C

Iron deficiency anemia

Fatigue, headache, irritability, exercise intolerance, pica, hair thinning

Hemoglobin, hematocrit, red cell indices, serum ferritin, iron, and iron-binding capacity

Multiple sclerosis

Intermittent intense pruritus, numbness, tingling in limbs, optic neuritis, vision loss, spasticity or weakness, vertigo

MRI

Cerebrospinal fluid analysis

Sometimes evoked potentials

Psychiatric illness†

Linear excoriations, presence of psychiatric condition (eg, clinical depression, delusions of parasitosis)

History and physical examination

Renal disease

End-stage kidney disease

Generalized pruritus, may be worse during dialysis, may be prominent on the back

Laboratory evaluation of renal function

Thyroid disorders*

Weight loss, heart palpitations, sweating, irritability (hyperthyroidism)

Weight gain, depression, dry skin and hair (hypothyroidism)

TSH, T4, anti-thyroid antibodies (to thyroid peroxidase and thyroglobulin)

Opioids

Antibiotics (eg, penicillin)

ACE inhibitors (eg, enalapril, ramipril)

Antimalarials (eg, hydroxychloroquine)

Statins (eg, atorvastatin)

Interleukin-2 agents (eg, aldesleukin)

Chemotherapeutic agents (eg, epidermal growth factor receptor inhibitors such as erlotinib, BRAF inhibitors such as vemurafenib)

Immune checkpoint inhibitors (eg, ipilimumab, pembrolizumab)

History of use

Typically history alone