- Clinical science
Pruritus is the medical term for itching of the skin. Pruritus may be generalized or localized, acute, or chronic. Localized pruritus is usually caused by dermatological conditions (e.g., allergic contact dermatitis), whereas generalized pruritus can also have systemic (e.g., uremia, hyperbilirubinemia), neurologic, psychogenic, or mixed causes. The evaluation of pruritus is based on a complete medical history and a detailed skin examination. Treatment of pruritus involves symptomatic relief and management of the underlying disease.
- Poorly understood
- Trigger; , i.e., mechanical, chemical, or thermal stimuli, as well as exposure to certain mediators (e.g., histamine, serotonin, prostaglandins, kinins) → activation of afferent C-fibers in the skin → interpreted by the CNS as pruritus
- Scratching and rubbing the skin → stimulation of inhibitory circuits and pain receptors → decreased pruritus in the short-term (however, in many patients, scratching increases irritation and ultimately worsens itching)
- Gate control theory: Painful input transmitted by A-fibers inhibits the transmission of pruritic input from the C-fibers.
- Initiating factors (e.g., contact with specific substances, drug intake, insect bites)
- Location: generalized vs. localized (see below)
- Acute vs. chronic (> 6 weeks)
- Time of day
- Travel and environmental history
- Underlying disorders (e.g., polycythemia vera) and medications (e.g., chloroquine)
- Psychiatric history
- Substance abuse (e.g., opioids, cocaine, and amphetamines)
- Goal: Determine whether there are primary skin lesions, secondary skin lesions (e.g., excoriations, lichenification), or no skin lesions at all.
- If skin lesions are visible, it is necessary to identify:
- Visible skin lesions are not always present.
- General physical examination: to determine the underlying disease (e.g., enlarged lymph nodes in Hodgkin disease, goiter in hyperthyroidism, jaundice in cholestasis)
Further evaluation depends on presentation and examination findings.
- Generalized pruritus
- Localized pruritus
- Skin disorders
- Medical therapy
- Systemic diseases
- Degeneration/compression of sensory nerve fibers
- Excoriation disorder: recurrent skin picking resulting in lesions and significant distress or impairment in daily functioning
- Substance use disorder
- Miscellaneous: advanced age
The differential diagnoses listed here are not exhaustive.
Secondary pruritus requires treatment of the underlying disease.
General and symptomatic measures
- Nonpharmacological: Moisturizers and/or calamine lotion (topical skin moisturizer)
- Topical application of glucocorticoids, calcineurin inhibitors, capsaicin, antihistamines, and anesthetics
- Systemic use of:
- Specific measures