Measurement of Electrical Current Perception Threshold of Sensory Nerves for Pruritus in Atopic Dermatitis Patients and Normal Individuals with Various Degrees of Mild Damage to the Stratum corneum

Abstract

Background: Patients with atopic dermatitis (AD) are well known to be sensitive to irritation from the environment due to the impaired function of the stratum corneum (SC). Electrical current perception threshold (CPT) evaluation quantifies the sensory threshold to transcutaneous electrical stimulation of the sensory nerves. Objective: To study the CPT in a noninvasive fashion using Neurometer^® CPT/C, together with measurements of various functions of the SC. Methods: We measured the CPT on the flexor forearm and cheek of AD patients and normal individuals. Subsequently, we evaluated the CPT and skin sensitivity to a 30% aqueous solution of lactic acid after the infliction of various mildly disruptive measures on the SC on the flexor forearm of healthy individuals by the following three methods: (1) removal of the superficial sebum with acetone/ether, (2) scarification with a needle and (3) tape stripping of the SC. Finally, we examined the effect of topical applications of emollients such as petrolatum or a moisturizing cream to the scratched skin. Results: AD patients showed a lower barrier function and lower CPT than normal individuals. In subsequent studies conducted in normal individuals, the CPT was found to be inversely correlated with transepidermal water loss (TEWL) levels after tape stripping. However, most of all, the partial superficial scarification with a needle decreased the CPT and increased the lactic acid stinging response. Prolonged removal of lipids from the SC with acetone/ether for 30 min that increased the TEWL levels for only 1 day decreased the high-frequency conductance value for 2 days and the CPT only on the 2nd day after treatment. Topical applications of emollients were effective to prevent the increased sensitivity caused by scratching. Conclusions: AD patients showed functional abnormalities of the SC and tended to have more sensitive skin on the cheek and flexor forearm than healthy controls. Even focal SC damage caused by superficial cracking may lead to further disruption of the already damaged SC in AD patients, by eliciting scratching and facilitating the permeation of various environmental allergens and also the induction of hypersensitive skin.

Olopatadine Ameliorates Rat Experimental Cutaneous Inflammation by Improving Skin Barrier Function

“…The barrier function in patients with AD is abnormal as evidenced by decreased water content, increased transepidermal water loss (TEWL) leading to decreased skin hydration [4,5] . In addition, it is well known that AD patients are sensitive to irritation from the environment due to abnormal function of the skin barrier [6] . Hyaluronic acid (HA) has an important regulatory role in the response of tissues to injury that occurs after skin barrier disruption [7] .…”

Bandeiraea Simplicifolia Isolectin B4 Binds Mast Cells in Human Skin and this Latter Binding is Up-Regulated in Patients with Atopic Dermatitis and Stinging

“…Recently, the dry skin in which the barrier is disrupted was found to tend to be more sensitive on the cheeks and flexor forearms of patients with atopic dermatitis patients to electronic currents that stimulate Aδ and C fibers than is the skin of healthy individuals [3]. Furthermore, the density of cutaneous nerves is higher in atopic skin than in corresponding regions of skin from healthy subjects [34,25].…”

“…Increased cutaneous sensitivity without visible signs of inflammation is referred to as stinging [3]. Skin of this type is prone to over-react to external factors and is diagnosed on the basis of its response to lactic acid, the so called stinger test [4].…”

Pruritus intensity assessment: challenge for clinicians

“…However, it was also suggested that subjects with chronic pruritus might also be more sensitive to itchy stimuli due to lowering of itch threshold at the periphery [37][38][39][40]. For instance, it was observed that tactile threshold in patients with nodular prurigo was lower than in controls and this abnormality was reversed by capsaicin, suggesting the involvement of neuropeptides, mainly substance P [37].…”

“…It was also demonstrated that electric stimulation might evoke pruritus in patients with chronic itch, making the threshold assessment relatively easy in clinical settings [41][42][43]. Kobayashi et al observed that patients with atopic dermatitis, a chronic inflammatory skin disease accompanied by severe itching, showed a lower barrier function and lower current perception threshold (CPT) than normal individuals, and the CPT was found to be inversely correlated with transepidermal water loss levels, a measurement of epidermal barrier disruption [38]. However, not all studies were able to demonstrate [41].…”