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.
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.
Kobayashi
Hiromi
H
Department of Dermatology, Tohoku University School of Medicine, Sendai, Japan.
Kikuchi
Katsuko
K
Tsubono
Yoshitaka
Y
Tagami
Hachiro
H
D000293:Adolescent; D000328:Adult; D003876:Dermatitis, Atopic / Q000150:complications / Q000503:physiopathology*; D005260:Female; D005712:Galvanic Skin Response / Q000502:physiology*; D006801:Humans; D008297:Male; D011537:Pruritus / Q000209:etiology / Q000503:physiopathology*; D012016:Reference Values; D011984:Sensory Receptor Cells / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology; D012867:Skin / Q000473:pathology*; D014870:Water Loss, Insensible / Q000502:physiology