Pruritus, or itch, is a common sensation that causes a person to want to scratch. It is a complex process that may negatively impact quality of life and commonly occurs with skin disorders such as atopic dermatitis and urticaria. It could also be a symptom related to an underlying disease process such as cholestasis or hyperthyroidism, or simply be caused by dry skin, especially in the cold, winter months. Therapy is often aimed at eliminating the underlying cause first, followed by the management of the itchy sensation. Treatment may include prescription and over-the-counter (OTC) medications, herbal remedies, hydrotherapy, phototherapy, and ultraviolet therapy. This overview provides information regarding the various management and treatment options for pruritus.
Pathophysiology of Pruritus
Pruritus is a complex process that involves the stimulation of free nerve endings found superficially in the skin. The sensation of pruritus is transmitted through the C-fibers in the skin to the dorsal horn of the spinal cord, and then, via the spinothalamic tract to the cerebral cortex for processing. Many chemicals have been found to be pruritogenic, therefore causing the itch sensation, including histamine, serotonin, cytokines, and opioids. There are six categories of pruritus: dermatologic, systemic, neurogenic, psychogenic, mixed, and other. Various treatment and management options exist depending on the category or cause.1
Treatment of pruritus can be categorized in several ways. A common method of grouping the various options is causative vs. symptomatic treatment. Causative treatment involves finding the underlying disorder and then correcting it, thereby eliminating the itch sensation. Symptomatic treatment involves substituting another sensation for the itch, using methods such as cooling, heating, or counter irritation (e.g., scratching). Symptomatic treatment can be used in addition to treating the underlying disease process in order to provide earlier relief. Most of the available treatment options are categorized under symptomatic therapy and management.
Prescription medications include topical and systemic antihistamines, corticosteroids, local anesthetics, and topical immunomodulators, among others. Some lower concentration preparations of these medications are available OTC.
Itching occurs when histamine is released, causing redness, swelling, warmth, and consequently itchiness. Antihistamines, or H1 antagonists, act by blocking the histamines, and are the most widely used medications for this condition. They take approximately 15–30 minutes to be effective and can be short- or long-acting.2
Topical antihistamines are available in prescription as well as nonprescription forms. Camphor (Caladryl®, Pfizer) is a common diphenhydramine preparation that has both antipruritic and anesthetic properties. This traditional therapy carries with it a small risk of contact dermatitis and allergic sensitization.3
Ultraviolet (UV) Light Therapy
UV phototherapy is used to treat various pruritic conditions including chronic renal failure; AD; HIV; aquagenic pruritus; solar, chronic, and idiopathic urticaria; urticaria pigmentosa; polycythemia vera; pruritic folliculitis of pregnancy; breast carcinoma skin infiltration; Hodgkin’s lymphoma; chronic liver disease; and acquired perforating dermatoses, among others. It is often undertaken after multiple attempts to treat stubborn itch, and can offer relief without many of the side-effects and risks of systemic medications. UV-based therapy utilizes UVB and UVA in both broadband and narrowband, as well as PUVA (psoralen UVA). Cost and side-effects can be a prohibitive factor for patients. Erythema is common in UVB, as is premature aging and photocarcinogenesis with both UVA and UVB. Side-effects associated with PUVA include redness, burning, headache, and nausea.16,19
UVA, UVB, and PUVA light therapies have been especially useful in the treatment of pruritus in HIV patients, as well as in those patients with systemic mastocytosis and cutaneous T-cell lymphoma. It localizes the effect on the superficial nerve endings, sparing the remaining helper cells, and relieving the pruritus. Because of its more superficial penetration, UVB is believed to be safer than UVA. UVB also spares the remaining helper cells in HIV patients and may localize the effect on the superficial nerve endings, thus relieving pruritus. Systemic mastocytosis and cutaneous T-cell lymphoma also respond to UV therapy and because destruction of the proliferating CD4 clone is desirable, UVA is usually the preferred modality over UVB, although Millikan suggests that the relief of pruritus is more predictable with UVB than with UVA.3
Cutaneous Field Stimulation (CFS)
CFS, which electrically stimulates thin afferent fibers, including nocireceptive C-fibers, was reported to inhibit histamine-induced itching. The reduction in itching is accompanied by degeneration of the epidermal nerve fibers. In one open trial, localized itching responded to CFS treatment, and pruritus was reduced by 49% at the end of 5 weeks. Itch relapsed gradually after the discontinuation of CFS, which led the researchers to conclude that nerve fibers regenerated into the epidermis.20
In addition to the nonprescription medications mentioned above, there are other OTC treatments that can be helpful for treating and managing pruritus. Moisturizing after a bath is extremely important, and emollients such as white petrolatum, or petrolatum depositing moisturizing body washes, and in-shower moisturizers (e.g., Olay® Ribbons®, Procter & Gamble; emulsifying ointment USP) can be helpful when applied while the skin is still wet.21
There is new evidence to show that moisturizers containing niacinamide and glycerin (e.g., Olay® Quench®, Procter & Gamble) not only hydrate the skin, but improve the skin’s resistance to external factors and improve the barrier function. Glycerin is required for moisturizers to work quickly and add moisture to the skin, but the niacinamide helps to sustain that benefit over a longer period of time.21
Several alternatives to traditional treatment of pruritus have been proposed. Often these therapies can be used in conjunction with prescribed or OTC medications to relieve symptoms quickly. Compounds that have been found to be effective for pruritus by depressing cutaneous sensory receptors include menthol, camphor, and phenol.7 Some other alternative therapies that have been suggested include herbal remedies, nutritional therapy, reflex therapy, and hydrotherapy.3
Several herbs have been proposed as corticosteroid-sparing agents and may provide a viable alternative to topical steroids and their side-effects. Oatmeal baths appear to be most useful because of its colloidal protein and high mucilaginous content. Other herbs have been suggested because of their high mucilage content as well, including flax, fenugreek, English plantain, hearts ease, marshmallow, mulberry, mullein, and slippery elm.3 More extensive research needs to be conducted regarding their possible use and effectiveness for the treatment of pruritus.
Tannins, also derived from herbs, may be helpful as well. The exact mechanism of action is unclear, but may perhaps be related to the coagulation of proteins in the skin. The most common tannin-containing herb is witch hazel, but others include oak bar, English walnut leaf, goldenrod, Labrador tea, lady’s mantel, lavender, and St. John’s wort.
Other possible herbs that may be advantageous include chamomile, which has shown to be equivalent to low concentrations of hydrocortisone, aloe vera, and capsaicin.3 Some side-effects may include irritant or allergic contact dermatitis. Some herbals can be toxic if ingested as well. Some of the oldest group of medications used to soothe and cool pruritic skin is menthol and camphor, which are both considered low risk and safe to use topically. 3,4
Nutritional therapy, despite not being sufficiently researched as a monotherapy for pruritus, may be helpful in combination with other anti-itch treatments. Vitamins D and E, and linolenic acid have shown some efficacy in the treatment of psoriasis and atopic eczema.3
Reflex Therapy, Acupuncture, and Hydrotherapy
While they are not traditionally used, reflex therapy, acupuncture, and hydrotherapy are three treatments that may be beneficial as adjunctive therapy, however further research is needed. There is little research available regarding the effectiveness of reflex therapy and hydrotherapy. These options may be considered in difficult-to-treat patients where traditional approaches have been unsuccessful. Acupuncture is based on the gate theory of neurotransmission, however it is infrequently used in the Western world, and therefore has insufficient evidence to fully support its use. 3
The management of symptoms is paramount in the treatment of pruritus. Patients should be educated regarding the self-care aspects of this condition. Eliminating the use of irritating or tight clothing is recommended, as well as maintaining a cool environment. Patients should avoid the frequent use of soap, topical irritants in clothing, dry environments, and vasodilators such as caffeine, alcohol, and hot water. Patients should be advised to take brief, tepid or lukewarm baths using mild cleansers with a low pH. Soap film should be rinsed off completely and skin should be patted lightly, followed by the generous application of a moisturizing lotion or cream.4,7,22
Pruritus is a common complaint, but one that can often be a challenge to treat. It can be a major quality of life issue for patients, so it is important that both the underlying disease and associated symptoms are treated as quickly and effectively as possible. Health teaching regarding the prevention and management of pruritus should be included in the overall treatment of the cause and symptoms.
P. Lovell, RN, BScN1; R. B. Vender, MD, FRCPC2
1. Michael DeGroote School of Medicine McMaster University
2. Dermatrials Research, Hamilton, ON, Canada