An electrical impedance technique for assessment of wheals

Abstract

In previous studies of the electrical impedance of the skin, we introduced a set of physical indices which could be used to distinguish between the cutaneous effects produced by different irritants and allergic contact reactions. In this study, wheals were induced in 10 allergic patients by performing prick tcsts on the forearm with the relevant allergen and histamine, respectively. Normal skin was used for control. The wheals were evaluated by visual scoring, laser Doppler, and electrical impedance. As expected. therc was a close agreement between the visual and laser Doppler readings. Compared to the controls. there were significant changes in the electrical impedance of the wheals. especially in the index related t o the phase angle. The changes in the indices were found to follow a particular pattern, which diverged from those obtained in contact skin reactions of both allergic and irritant type. Our results indicate that, by the application of the impedance technique, it will be possible to characterize objectively and quantify the wheal reaction. The results also suggest that cutaneous reactions of completely different causes, such as allergic skin reactions of the late and immediate type, and irritant contact reactions, may be distinguished on the basis of their effects on the electrical impedance of the skin.In the clinic, visual inspection and measurement of size are the normal way of evaluating wheals, and the results show some variability depending on the observer (1). More objective methods of assessment have been used such as ultrasound and laser Doppler flowmetry (LDF) (2-4). We have recently described a noninvasive method based on electrical impedance which seems to be a suitable tool for skin investigations (5-7).This study aimed to evaluate the electrical impedance technique for the investigation of immediate skin reactions induced by common inhalant allergens, and to see whether the patterns of the impedance indices differ from the ones obtained in our studies on contact reactions. Material and methods Test siibjectsTen white volunteers, six women and four men, aged 1 8 4 3 years (mean 34 years), participated in the study.

Assessment of skin lesions and skin cancer using simple electrical impedance indices

“…Skin impedance has been used in many applications, for example classification (4) and quantification (5, 6) of skin irritations, differentiation between type I diabetics skin and reference skin (7), and evaluation of allergic reactions (8, 9).…”

On Assessment of Skin Reactivity Using Electrical Impedancea

“…In 10 allergic patients, on which prick tests of relevant antigens were performed on the volar forearm and compared to the controls, there were significant changes in the impedance parameters of the wheals, especially in the index related to the phase angle (Table 1). 19 The patterns of the statistically significant changes of the impedance indices differed from those obtained in contact skin reactions of both allergic and irritant types. Also, the results indicated that the allergic skin reactions of the immediate type could be characterized by the impedance technique, and the instrument is a candidate tool for evaluation of the efficacy of antihistamines.…”

Prick test: evolution towards automated reading

“…Nyren et al performed several tests based on this idea. The method had already been applied to the study of eczema and skin reactions, but its application to allergic wheals had not yet been carried out.…”