Some Causes of Itching
Cause | Suggestive Findings | Diagnostic Approach |
|---|---|---|
Primary skin disorders | ||
Presence of erythema, possible lichenification, keratosis pilaris, xerosis, Dennie-Morgan lines, hyperlinear palms Usually a family history of atopy or chronic recurring dermatitis | Clinical examination alone | |
Dermatitis secondary to contact with allergen; erythema, vesicles | Clinical examination alone | |
Dermatophytosis (eg, tinea capitis, tinea corporis, tinea cruris, tinea pedis) | Localized itching, 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 |
Areas of skin thickening secondary to repetitive scratching Lesions are discrete, erythematous, scaly plaques, well-circumscribed, rough, lichenified skin | Clinical examination alone | |
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 | |
Plaques with silvery scale typically on extensor surfaces of elbow, knees, scalp, and trunk Itching not necessarily limited to plaques Possibly small-joint arthritis manifesting as stiffness and pain | Clinical examination alone | |
Small erythematous or dark papules at one end of a fine, wavy, slightly scaly line up to 1 cm long (burrow); 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 itching | Clinical examination Microscopic examination of skin scrapings from burrows | |
Evanescent, circumscribed, raised, erythematous lesions with central pallor Can be acute (< 6 weeks) or chronic (≥ 6 weeks) | Clinical examination alone | |
Xerosis (dry skin) | Most common in the winter Itchy, dry, scaly skin, mostly on lower extremities Exacerbated by dry heat | Clinical examination alone |
Systemic disorders | ||
Allergic reaction, internal (numerous ingested substances) | Generalized itching, rash with macules and papules or urticarial rash May or may not have known allergy | Trial of avoidance Sometimes skin-prick testing |
Cancer (eg, Hodgkin lymphoma, polycythemia vera, mycosis fungoides) | Itching may precede any other symptoms Burning quality to itching, primarily in lower extremities (Hodgkin lymphoma) Itching after bathing (polycythemia vera) Heterogeneous cutaneous lesions—plaques, patches, tumors, erythroderma (mycosis fungoides) | 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 itching without rash, developing sometimes in late pregnancy | Liver tests |
Urinary frequency, thirst, weight loss, vision changes | Urine and blood glucose HbA1C | |
Fatigue, headache, irritability, exercise intolerance, pica, hair thinning | Hemoglobin, hematocrit, red cell indices, serum ferritin, iron, and iron-binding capacity | |
Intermittent intense itching, 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) | Clinical examination Diagnosis of exclusion |
Renal disease | End-stage renal disease Generalized itching, may be worse during dialysis, may be prominent on the back | |
Thyroid disorders* | Weight loss, heart palpitations, sweating, irritability (hyperthyroidism) Weight gain, depression, dry skin and hair (hypothyroidism) | TSH, T4 |
Medications | ||
History of use | Clinical examination alone | |
* Itching as the patient’s presenting complaint is unusual. | ||
HbA1C = glycosylated hemoglobin; KOH = potassium hydroxide; T4 = thyroxine; TSH = thyroid-stimulating hormone. | ||