Scratching and noxious heat stimuli inhibit itch in humans: a psychophysical study.

BACKGROUND: Patients who suffer from chronic itch employ creative techniques to alleviate their itch, often using painful thermal stimuli, such as hot and very cold showers, as well as mechanical stimuli, such as scratching. OBJECTIVES: The present study examined whether the sensory perception of itch is attenuated by remote interactions between both thermal and mechanical stimuli and afferent information related to itch. PATIENTS AND METHODS: Itch was induced with histamine iontophoresis in 21 healthy young subjects. Repetitive thermal stimuli including innocuous warmth, innocuous cool, noxious cold and noxious heat as well as scratching were applied 3-cm distal to the area of histamine iontophoresis. Subjects rated their perceived intensity of histamine-induced itch with a computerized visual analogue scale. RESULTS: Itch intensity ratings were significantly reduced during each period of scratching and repeated noxious heat and cold. Innocuous cooling and warming did not significantly alter itch intensity ratings. Inter-individual differences in histamine-induced itch sensitivity were unrelated to inter-individual differences in pain sensitivity. CONCLUSIONS: The present psychophysical study demonstrates that repetitive noxious thermal and scratching stimuli inhibit itch and do not require direct physical interaction with the area of the skin from which itch originates.

Uremic pruritus is associated with higher kt/V and serum calcium concentration.

BACKGROUND: The prevalence and characteristics of uremic pruritus have not recently been investigated in a US dialysis cohort. This study examined uremic pruritus and associated risk factors in hemodialysis patients treated in the year 2005. METHODS: The prevalence and characteristics of pruritus (short version McGill pain questionnaire), severity (10 cm visual analogue scale), and effect on quality of life (Skindex-16) were determined in thrice weekly hemodialysis patients. Daugirdas single-pool Kt/V, clinical and laboratory data were recorded. RESULTS: 105 of 307 screened hemodialysis patients met inclusion criteria and were evaluated, 49% (151) were excluded due to advanced age, 3% (9) other skin diseases, and 14% (42) refused. Participants were 55% male (58/105) and 65% African-American (68) with a mean +/- SD age of 48 +/- 11 years. The overall prevalence of pruritus was 57% (60/105, 95% CI 47 - 67%) and a positive correlation was observed between the presence of uremic itch and serum calcium concentration (p = 0.04). Intact PTH and serum phosphorus concentration were not associated with either the presence or intensity of itch. Intensity of pruritus was positively correlated with increasing months on dialysis (64 +/- 63 vs. 51 +/- 46 months for itch and non-itch, respectively; p = 0.02), higher Kt/V (1.82 +/- 0.7 vs. 1.70 +/- 0.56 for itch and non-itch, respectively; p = 0.01) and skin dryness (p = 0.01). Patients receiving statins were significantly less likely to report pruritus (p = 0.02) and uremic itch adversely impacted several aspects of quality of life. CONCLUSIONS: Pruritus remains a common and significant symptom in adequately hemodialyzed patients. Higher serum calcium concentrations, longer durations of ESRD and higher Kt/V appear to be important factors associated with uremic pruritus.

Over-the-counter topical antipruritic agents are commonly recommended by office-based physicians: an analysis of US practice patterns.

BACKGROUND: Pruritus is one of the most common complaints among patients who visit physicians. Over-the-counter topical antipruritic medications are widely recommended by physicians and are self-administered by patients for the treatment of pruritus. However, there are few scientific controlled studies evaluating the effect of these drugs on pruritus. OBJECTIVES: To assess the role of physician-recommended over-the-counter medications for the treatment of pruritus. METHODS: Records were analyzed for office-based physician visits in which over-the-counter antipruritic topical medications were recommended in the National Ambulatory Medical Care Survey between the years 1995 and 2000. RESULTS: The largest proportion of over-the-counter antipruritic agent recommendations were during visits to dermatologists, accounting for 41% of all such recommendations. Other physicians that recommended such agents included family physicians and pediatricians, accounting respectively for 26% and 21% of the recommendations. The most commonly recommended over-the-counter medications included hydrocortisone preparations (72%) and diphenhydramine (15%). Over-the-counter medications were more frequently recommended in the pediatric age group. CONCLUSION: This study demonstrates that over-the-counter medications are frequently recommended for the treatment of pruritus.