Neuroselective transcutaneous electric stimulation reveals body area–specific differences in itch perception

Cowhage-induced itch scores and the current perception threshold in assessing sensitive skin: An observational laboratory study

BACKGROUND

The diagnosis of sensitive skin remains nonuniform, and the underlying mechanism is unclear. Previous studies were inconsistent in the current perception threshold (CPT) measurement for sensitive skin; thus, the neural sensitivity of sensitive skin needs to be clarified.

OBJECTIVES

This study aimed to compare the CPT measurement and the cowhage test for sensitive skin and to investigate the correlation between CPT values and cowhage-itch scores.

METHODS

Participants with and without sensitive skin (n = 30, 30) were included. The cowhage test and CPT measurement with its related sensations were performed.

RESULTS

No difference was found in CPT between the sensitive and nonsensitive groups at either the site of the face or the forearm (5, 250, or 2000 Hz). Once the CPT was reached, sensations (itch, stinging, and throbbing) were significantly different between the two groups. Cowhage provoked more intense itch with a longer duration in the face (visual analog scale [VAS] score 1.90 ± 1.47 vs. 0.52 ± 0.90, p < 0.001; duration 3.80 ± 3.31 vs. 0.87 ± 1.43 min, p < 0.001) and forearm (VAS 2.53 ± 2.60 vs. 0.72 ± 1.06, p < 0.001; duration 3.37 ± 3.46 vs. 1.33 ± 2.14 min, p < 0.01) of the sensitive group compared with the nonsensitive group. Cowhage-induced itch and CPT-related itch (5 Hz) showed moderate correlations in both the face (r = 0.441, p < 0.001) and forearm (r = 0.491 p < 0.001) and weak correlations in the forearm (r = 0.323 at 250 Hz, p = 0.012; r = 0.376 at 2000 Hz, p = 0.003).

CONCLUSIONS

Cowhage test showed better performance in assessing the neural sensitivity of sensitive skin in comparison with the CPT measurement. Evaluation of CPT-related sensations may add valuable information to sensitive skin assessment.

Characterization of Cowhage-induced Pruritus in Sensitive Skin: An Observational Laboratory Study

Sensitive skin is a prevalent syndrome, characterized by discomfort in response to mild stimuli, which impacts on quality of life. Pruritus is one of the major symptoms of sensitive skin. However, the pathomechanism of sensitive skin is insufficiently understood. As an experimental model for pruritus, the cowhage skin prick test might provide insight into the understanding of sensitive skin. This study aimed to specify the characteristics of cowhage-induced pruritus in sensitive skin. Female volunteers, 20 with sensitive skin and 20 controls, were recruited. Self-report questionnaires were distributed and the responses evaluated; moreover, alongside assessments by dermatologists, skin physiology assessments, lactic acid sting test, capsaicin test and cowhage skin challenge were performed. Pruritus in sensitive skin was perceived as more intense and longer-lasting than in normal skin, with different qualities of accompanying sensations. Cowhage skin challenge results showed moderate consistency with clinical assessments. The results suggest that cowhage skin challenge could be a new tool for the assessment of sensitive skin.

Efficacy of pregabalin for the treatment of chronic pruritus of unknown origin, assessed based on electric current perception threshold

Chronic pruritus of unknown origin (CPUO) is defined as itching lasting more than 6 weeks in the absence of discernible skin lesions. Pregabalin is used to treat patients with CPUO. In this study, we aimed to investigate differences in the perception threshold of itch sensation between patients with CPUO and healthy individuals and to evaluate the efficacy of pregabalin for CPUO. At baseline, week 2, and week 4 after treatment initiation, the visual analogue scale (VAS) score was measured to assess pruritus severity, and electric current perception threshold (CPT) was measured at 250 and 5 Hz using a NEUROMETER CPT/C stimulator. Twenty healthy individuals and 41 patients with CPUO were enrolled in this study. The patients with CPUO were categorised as those who responded to antihistamines (Antihistamine group), were not improved by antihistamines (Pregabalin group), and were not improved by antihistamines and pregabalin (Refractory group). The baseline CPT values were not significantly different between patients with CPUO and healthy control. Pruritus was improved in 7 of 10 patients in the Pregabalin group after treatment with pregabalin, showing decreased CPT at 5 Hz. The sensitive C-fibres presented a high threshold to detect itch sensation, and this sensitivity decreased in response to treatment with pregabalin.

Prevalence and Clinical Characteristics of Itch in Vitiligo and Its Clinical Significance

Objective

Vitiligo usually presented as asymptomatic depigmented macules and patches. Little is known regarding itch in vitiligo. This study aimed to evaluate the prevalence and characteristics of itch in vitiligo patients.

Patients and Methods

A cross-sectional study was conducted on vitiligo patients. Itch character and intensity were determined through questionnaires. Evaluation was also made by dermatologists to define vitiligo subtype, body surface area, Koebner phenomenon (KP), and so on. Data were assessed by computer software. Results were considered statistically significant if p < 0.05.

Results

Among 402 patients, itch on vitiliginous lesion presented in 20.2%. Prevalence of itch was most common in focal vitiligo (29.4%), followed by segmental vitiligo (20.3%) and nonsegmental vitiligo (19.6%), respectively. Tingling sensation was the most common itch-related symptom (82.7%). The median itch intensity is 5 by 10-point visual analog scale. Daily activity and sleep disturbance were observed in 60.5% and 39.5% of patients who experience itch. Itch occurred approximately 3 days prior to the development of lesions in 48.1% of patients. Thirty-two patients (78.1%) with both itch and KP type IIb had active disease.

Conclusions

Itch in vitiligo is not uncommon. The presence of itch with KP type IIb may warrant the active vitiligo.

Use of transcutaneous electrical nerve stimulation for chronic pruritus

Pruritus is a distressing symptom in many dermatological as well as systemic conditions, and it is sometimes very chronic and relapsing. Transcutaneous electrical nerve stimulation (TENS) is an inexpensive form of analgesia that could also ameliorate itching. This study aimed to evaluate TENS efficacy in patients with pruritus due to some types of chronic eczema, and in patients with chronic hepatic disease. Ten patients with atopic dermatitis (AD), 20 patients with lichen simplex chronicus (LSC), and 16 patients with chronic liver disease having chronic distressing pruritus received three sessions of TENS weekly for 12 sessions, and the effect on the visual analogue scale (VAS) scores was recorded after 2 weeks of therapy, at treatment end, and after an additional month for follow up. There was a statistically significant decline in the mean VAS score for studied groups at weeks 2 and 4 of therapy compared to baseline, but the improvement was more significant in patients with AD, and LSC (p < 0.001 for both) than in those with chronic liver disease (p < 0.01) who also showed an early re-elevation of VAS score on follow up. TENS therapy holds promise as a palliative, alternative, safe and inexpensive treatment for patients with some chronic pruritic conditions.

N-palmitoylethanolamine and N-acetylethanolamine are effective in asteatotic eczema: results of a randomized, double-blind, controlled study in 60 patients

BACKGROUND

Asteatotic eczema (AE) is characterized by itchy, dry, rough, and scaling skin. The treatments for AE are mainly emollients, usually containing urea, lactic acid, or a lactate salt. N-palmitoylethanolamine (PEA) and N-acetylethanolamine (AEA) are both endogenous lipids used as novel therapeutic tools in the treatment of many skin diseases. The purpose of this study was to compare a PEA/AEA emollient with a traditional emollient in the treatment of AE.

METHODS

A monocentric, randomized, double-blind, comparative trial was conducted in 60 AE patients to evaluate and compare the efficacy of the two emollients. The level of skin dryness among the subjects ranged from mild to moderate. The subjects' skin barrier function and the current perception threshold were tested for 28 days by clinical scoring and bioengineering technology.

RESULTS

The results showed that, although some aspects were improved in both groups, the group using the emollient containing PEA/AEA presented a better skin surface change in capacitance. However, the most impressive finding was the ability of the PEA/AEA emollient to increase the 5 Hz current perception threshold to a normal level after 7 days, with a significant difference between values at baseline and after 14 days. A current perception threshold of 5 Hz was positively and significantly correlated with skin surface hydration and negatively correlated with transepidermal water loss in the PEA/AEA emollient group.

CONCLUSION

Compared with traditional emollients, regular application of a topical PEA/AEA emollient could improve both passive and active skin functions simultaneously.

Differences in peripheral endocannabinoid modulation of scratching behavior in facial vs. spinally-innervated skin

Cannabinoids suppress nocifensive behaviors in rodents. We presently investigated peripheral endocannabinoid modulation of itch- and pain-related behaviors elicited from facial vs. spinally-innervated skin of rats. Intradermal (id) injection of the pruritogen serotonin (5-HT) elicited significantly more hindlimb scratch bouts, and longer cumulative time scratching, when injected in the rostral back compared to the cheek. Pretreatment of skin with inhibitors of degrading enzymes for the endocannabinoids anandamide (URB597) or 2-arachidonoylglycerol (JZL184) significantly reduced scratching elicited by 5-HT in the rostral back. These effects were prevented by co-treatment with antagonists of the CB₁ (AM251) or CB₂ receptor (AM630), implicating both receptor subtypes in endocannabinoid suppression of scratching in spinally-innervated skin. Conversely, pretreatment with either enzyme inhibitor, or with AM630 alone, increased the number of scratch bouts elicited by id 5-HT injection in the cheek. Moreover, pretreatment with JZL184 also significantly increased pain-related forelimb wipes directed to the cheek following id injection of the algogen, allyl isothiocyanate (AITC; mustard oil). Thus, peripheral endocannabinoids have opposite effects on itch-related scratching behaviors in trigeminally- vs. spinally-innervated skin. These results suggest that increasing peripheral endocannabinoid levels represents a promising therapeutic approach to treat itch arising from the lower body, but caution that such treatment may not relieve, and may even exacerbate, itch and pain arising from trigeminally-innervated skin of the face or scalp.

The itchy scalp--scratching for an explanation

Scalp pruritus is a common complaint that is considered a diagnostically and therapeutically challenging situation. Scalp skin has a unique neural structure that contains densely innervated hair follicles and dermal vasculature. In spite of the recent advances in our understanding of itch pathophysiology, scalp itching has not been studied as yet. In this review, we summarize the current knowledge on the neurobiology of scalp and hair follicles as well as itch mediators and provide a putative mechanism for scalp itch with special emphasis on neuroanatomy and pathophysiology.

Diferenças de gênero no limiar sensitivo para estimulação elétrica nervosa em adultos jovens

OBJETIVO: Investigar diferenças de gênero no limiar neuronal sensitivo (LNS) para estimulação elétrica nervosa transcutânea (TENS) entre adultos jovens, e os presumíveis efeitos da termoterapia prévia. MÉTODOS: Foram divididos por gênero, 30 estudantes jovens sadios (15 homens e 15 mulheres entre 6/11 ciclo estral) com 22±2 anos de idade. TENS foi aplicada simultaneamente nos joelhos direito e esquerdo dos sujeitos com frequência de 20 Hz e duração de pulso 230µs. A amplitude da corrente elétrica (mǺ) foi aumentada gradativamente para registro do limiar de percepção (LS) e tolerância (LT), antes/após termoterapia. O aquecimento no joelho-D foi realizado por luz infravermelha (250 W) à 0≈70 cm perpendicularmente, e o resfriamento do joelho-E por compressa de gelo, ambos realizados durante 15 minutos. A temperatura tecidual foi registrada por termometria digital. Os dados foram analisados e diferenças estabelecidas em p<0.05. RESULTADOS: A temperatura tecidual após termoterapia foi diferente (p<0.05) entre gêneros. No LS basal para TENS não houve diferenças entre gêneros, porém, a termoterapia alteou o LS em ambos os sexos. O LT basal foi menor (p<0.05) em mulheres, entretanto, após a termoterapia aumentou (p<0.05) em ambos os sexos. CONCLUSÃO: Os LNS para TENS são gênero-termo-dependentes em jovens sadios.

Influence of acupuncture on type I hypersensitivity itch and the wheal and flare response in adults with atopic eczema - a blinded, randomized, placebo-controlled, crossover trial

BACKGROUND

Itch is a major symptom of allergic skin disease. Acupuncture has been shown to exhibit a significant effect on histamine-induced itch in healthy volunteers. We investigated the effect of acupuncture on type I hypersensitivity itch and skin reaction in a double-blind, randomized, placebo-controlled, crossover trial.

METHODS

An allergen stimulus (house dust mite or grass pollen skin prick) was applied to 30 patients with atopic eczema before (direct effect) and after (preventive effect) two experimental approaches or control observation: acupuncture at points Quchi and Xuehai [verum acupuncture (VA), dominant side], 'placebo-point' acupuncture (PA, dominant side), no acupuncture (NA). Itch intensity was recorded on a visual analogue scale. After 10 min, wheal and flare size and skin perfusion (via LASER-Doppler) were measured at the stimulus site, and the validated Eppendorf Itch Questionnaire (EIQ) was answered.

RESULTS

Mean itch intensity was significantly lower in VA (35.7 +/- 6.4) compared to NA (45.9 +/- 7.8) and PA (40.4 +/- 5.8) regarding the direct effect; and significantly lower in VA (34.3 +/- 7.1) and PA (37.8 +/- 5.6) compared to NA (44.6 +/- 6.2) regarding the preventive effect. In the preventive approach, mean wheal and flare size were significantly smaller in VA (0.38 +/- 0.12 cm(2)/8.1 +/- 2.0 cm(2)) compared to PA (0.54 +/- 0.13 cm(2)/13.5 +/- 2.8 cm(2)) and NA (0.73 +/- 0.28 cm(2)/15.1 +/- 4.1 cm(2)), and mean perfusion in VA (72.4 +/- 10.7) compared to NA (84.1 +/- 10.7). Mean EIQ ratings were significantly lower in VA compared to NA and PA in the treatment approach; and significantly lower in VA and PA compared to NA in the preventive approach.

CONCLUSIONS

Acupuncture at the correct points showed a significant reduction in type I hypersensitivity itch in patients with atopic eczema. With time the preventive point-specific effect diminished with regard to subjective itch sensation, whereas it increased in suppressing skin-prick reactions.

Patients' perspective of pruritus in chronic plaque psoriasis: a questionnaire-based study

BACKGROUND

Pruritus in psoriasis patients has not been regarded as a major symptom. Objective To study the pattern of pruritus in chronic plaque psoriasis.

METHODS

A questionnaire was sent out to 109 patients with a diagnosis of chronic plaque psoriasis, who attended our outpatient departments during the period of January 2006 to January 2007.

RESULTS

Out of 109 patients, 80 patients (74%) answered the questionnaire. Pruritus was found in 80% of the patients, with an intensity of 5.2 +/- 2.6 (+/-SD) using a visual analogue scale (0-10). The frequency and intensity of pruritus were higher in women. Lower leg and scalp were reported to be the most commonly affected sites. Major aggravating factors for pruritus were stress and dryness of skin. Sun, sleep and vacation could relieve pruritus. The most common antipruritic treatments used by the patients were topical steroids, topical vitamin D, emollients and ultraviolet light therapy, whereas antihistamines were used by a small number of patients. Mood, concentration and sleep were negatively affected by pruritus.

CONCLUSION

Pruritus is a common symptom in patients with chronic plaque psoriasis.