FEATURE ARTICLE The Clinical Conundrum of Pruritus Victoria Garcia-Albea, Karen Limaye ABSTRACT: Pruritus is a common complaint for derma- Pruritus is also the most common symptom in derma- tology patients. Diagnosing the cause of pruritus can tological disease and can be a symptom of several sys- be difficult and is often frustrating for patients and pro- temic diseases (Bernhard, 1994). The overall incidence viders. Even after the diagnosis is made, it can be a chal- of pruritus is unknown because there are no epidemio- lenge to manage and relieve pruritus. This article reviews logical databases for pruritus (Norman, 2003). According common and uncommon causes of pruritus and makes to a 2003 study, pruritus and xerosis are the most com- recommendations for proper and thorough evaluation mon dermatological problems encountered in nursing and management. home patients (Norman, 2003). Key words: Itch, Pruritus INTRODUCTION ETIOLOGY Pruritus (itch) is the most frequent symptom in derma- The skin is equipped with a network of afferent sensory tology (Serling, Leslie, & Maurer, 2011). Itch is the pre- and efferent autonomic nerve branches that respond to dominant symptom associated with acute and chronic various chemical mediators found in the skin (Bernhard, cutaneous disease and is a major symptom in systemic dis- 1994). It is believed that maximal itch production is ease (Elmariah & Lerner, 2011; Steinhoff, Cevikbas, Ikoma, achieved at the basal layer of the epidermis, below which & Berger, 2011). It can be a frustration for both the patient pain is perceived (Bernhard, 1994). Autonomic nerves in- and the clinician. This article will attempt to provide an nervate hair follicles, pili erector muscles, blood vessels, overview of pruritus, a method for thorough and com- eccrine, apocrine, and sebaceous glands (Bernhard, 1994). plete evaluation and possible treatment modalities. Afferent sensory nerves transmit noxious stimuli and cold The word pruritus stems from the Latin prurire,which (Stander et al., 2003). Roughly 10% of afferent C fibers means ‘‘to itch’’ (Merriam-Webster, 2009). Itch has been respond to itch and thermal stimuli and not to painful defined as an unpleasant feeling associated with the urge or mechanical stimuli (Stander et al., 2003). Schmelz, to scratch, exclusive to the skin (Stander et al., 2003). Schmidt, Bickel, Handwerker, and Torebjork (1997) showed It can be induced by chemical mediators and by physical that there is one subset of primary afferent C fibers that is and thermal stimuli (Stander et al., 2003). Its biological almost exclusively histamine sensitive and is probably the purpose is likely to have originated from when pruritic primary afferent nerve that carries the itch sensation. agents were mainly parasites (Stander et al., 2003). A mediator of itch is any substance that causes the sensation of itching and the desire to scratch when in- INCIDENCE troduced into the skin (Bernhard, 1994). A number of ‘‘Itching is the most characteristic and distressing symp- chemical mediators have been shown to induce pruritus tom of diseases of the skin’’ (Bernhard, 1994, p. 37). and are, therefore, felt to play a role in various diseases that result in itch. Histamine is the best-known pruritogen. Victoria Garcia-Albea, CPNP, MSN, Mystic Valley Dermatology, It was first described in the 1920s and is considered the Stoneham, Massachusetts. ‘‘prototypic chemical mediator of itch’’ (Bernhard, 1994, Karen Limaye, FNP, MSN, Department of Dermatology, Lahey p. 26). A biogenic amine, histamine is found in mast Clinic, Burlington, Massachusetts. cells and keratinocytes and is activated by immunoglob- The authors and planners have disclosed that they have no finan- ulin E (IgE), cytokine 5a, substance P, immunoglobulin G cial relationships related to this article. (IgG), and nerve growth factor. Histamine produces itch Correspondence concerning this article should be addressed to Victoria Garcia-Albea, CPNP, MSN, Mystic Valley Dermatology, primarily via the Histamine 1 (H1) receptor, and less so 92 Montvale Ave., Suite 300, Stoneham, MA 02180. via the H2 and H3 receptors. Serotonin, another bio- E-mail: [email protected] genic amine, is a weak pruritogen found in human plate- DOI: 10.1097/JDN.0b013e31824abb10 lets. Serotonin activates mast cells to release histamine. VOLUME 4 | NUMBER 2 | MARCH/APRIL 2012 97 Copyright © 2012 Dermatology Nurses' Association. Unauthorized reproduction of this article is prohibited. However, when injected into the skin, it causes a pricking, with pruritus report that symptoms get worse at bedtime. painful itch only in some people. Serotonin is involved in Different body parts are disproportionately prone to itch; the central sensation of pruritus and the opioid neuro- ear canals, eyelids, nostrils, perianal and genital areas are transmitter system (Bernhard, 1994). especially susceptible to pruritus (Bernhard, 1994). Because nerves carry the itch sensation, researchers have studied the role of neuropeptides as itch mediators EVALUATION (Bernhard, 1994). Substance P, a neuropeptide, is found A thorough evaluation is necessary in identifying pru- in the cell bodies of C neurons. It is transported toward ritic etiology, because it must be determined whether the the peripheral nerve terminals and released by depolar- patient’s itch is due to a primary dermatological disease, ization to activate dermal mast cells to release histamine, systemic disease, or another cause (Bernhard, 1994). Par- cause vasodilation, and increase vascular permeability. ticular attention must be paid to the onset, nature, du- Substance P is distributed all over the body, including the ration, severity, location, relationship to activities, time dermis and probably the epidermis. It is a potent itch relation, and precipitating, alleviating, and exacerbating inducer, whose pruritic effects can be blocked by proper factors (Table 1). Other pertinent information includes administration of oral antihistamines (Bernhard, 1994). medications, allergies, atopic history, family history of Other chemical mediators involved in itch include ace- atopy or skin disease, occupation, hobbies, social history, tylcholine, bradykinin, tryptase, endothelin, vanilloids, bathing habits, pets, travel history, and prior diagnoses and proteinases (Bernhard, 1994; Stander et al., 2003). (Table 1). Risk factors for human immunodeficiency virus Prostaglandins, interleukins, and nerve growth factor all (HIV) should be assessed, because itch can be an early exaggerate existing itch (Bernhard, 1994; Stander et al., sign of HIV infection. Complaint of interference with 2003). Opioid peptides modify the peripheral and central sleep patterns can be very helpful in making the diagnosis sensations of pruritus (Stander et al., 2003). Antagonizing since some conditions, such as scabies infestation, can be endogenous opioids suppress localized and systemic pru- ritus (Stander et al., 2003). However, morphine, which is a powerful exogenous opioid analgesic, ironically can in- TABLE 1. History of Present Illness and duce intractable itching (Bernhard, 1994). Morphine Pertinent History for Patients With Pruritus induces histamine release from mast cells, but antihis- (Bernhard, 1994) tamines do not prevent or relieve morphine-induced itch (Bernhard, 1994). Description of Itch Pertinent History Cannabinoid receptor agonists have been shown to re- Onset: sudden or gradual Medications: prescription, duce histamine-induced nerve excitation (Stander et al., Nature: continuous, herbal, over the 2003). Two cold receptors that act as desensitizers have intermittent, burning, counter, illicit been found. When skin temperature was reduced, the sen- pricking Allergies: medications, sation of experimentally induced itch was reduced. Sim- Duration:minutes,hours, environmental ilar results, without a decrease in temperature, were days, weeks Atopic history: asthma, achieved when topical menthol was applied to the skin Severity: does it interfere allergies, eczema (Stander et al., 2003). with normal activity Family history of atopy or Time relation: bedtime, skin disease TYPES OF ITCH cyclical Occupation Pruritoceptive itch refers to sensations that arise in af- Location: localized, Hobbies: chemical ferent C nerve fibers and are often due to inflammation, generalized, unilateral or exposures xerosis, or trauma in the dermo-epidermal junction sur- bilateral, scalp Social history: personal rounding the fiber tips (Bernhard, 1994). The sensation Relationship to activities: contacts is then transmitted to the thalamus and sensory cortex worse at work or when via the spinothalamic tract. Neuropathic itch arises when Bathing habits: frequency, doing hobbies temperature of water, a disease process involves the afferent pathway, such as in Provoking factors: heat, type of soap herpes zoster. Central or neurogenic itch is less well un- exercise, water Pets derstood than other types of itch. It arises from a systemic Alleviating factors: distraction, etiology that may involve peripheral cutaneous mediators, Sexual history antihistamines, cool Climate/season such as in severe cholestasis (Bernhard, 1994). compresses Travel history PATTERNS OF ITCHING Prior diagnoses: by The pattern of itch varies from person to person and healthcare providers or can vary within an individual (Bernhard, 1994). Among patient’s own theories aggravating factors, heat is usually a culprit, as is stress, HIV risk factors absence of distractions, anxiety, and fear. Most patients 98 Journal of