No abstract

As with other non-invasive techniques, baseline characteristics differ from place to place over the body surface, and age is another important determining factor.

A new, non-invasive device, which enables local measurements of electrical impedance to a controlled depth, has been used to evaluate the degree of irritation in human skin. The results have been compared with those obtained using other non-invasive techniques, i.e. with transepidermal water loss (TEWL), electrical capacitance moist measurement (ECM), laser-Doppler flowmetry (LDF), and visual scoring. Sodium lauryl sulphate solutions (0.1-5.0%), and a blank, were applied in Finn Chambers for 24 h on the volar forearm of 10 healthy volunteers. Values were recorded before application of the test chambers, and at 1 h, 24 h, 1 week and 2 weeks after removal. Thus, both the degree of initial damage and the healing process were monitored. There was close agreement among values obtained using electrical impedance, TEWL and visual readings. Results obtained using ECM and LDF were not consistent with the other three methods. In evaluating irritation of the skin, the practical situation may influence the choice of bioengineering tools. In most circumstances, a combination of methods would be preferable.

Urea has long been used to treat dry skin. In the present report, we compared two creams, identical with the exception that one contained both urea and sodium chloride and the other urea alone, in 22 patients with atopic dermatitis. Following a 2-week wash-out period, their clinically non-eczematous, rough or normal-appearing skin on the forearms was treated twice daily in a double-blind and randomised manner. We examined the treated areas by measuring transepidermal water loss, capacitance and electrical impedance. Our findings suggest that a moisturiser containing both urea and sodium chloride seems somewhat more effective than the same moisturiser without sodium chloride, at least concerning the ability to reverse impedance indices of atopic skin towards normal, an effect ascribed mainly to changes in hydration of the stratum corneum. However, the clinical significance of our impedance measurements is somewhat premature to decide.

No abstract

Patients with eczema and other dry skin conditions use moisturizers also when the skin appears healthy. However, moisturizers have been found to change skin barrier function, and it appears that certain combinations of ingredients increase the skin susceptibility to external agents. In the present randomized and single-blind study, the influence of a urea-containing cream on nickel susceptibility in 35 patients with known allergy to nickel was evaluated. Treatment of the volar forearm twice daily for 20 days with the urea cream reduced transepidermal water loss (TEWL). However, the susceptibility to nickel sulfate was not changed by the cream treatment. Clinical scoring of the skin reaction did not show any difference between the untreated and the cream-treated area. Furthermore, the increase in TEWL did not differ between the areas. The absence in correlation between TEWL and skin susceptibility to nickel suggests different penetration pathways through the skin of water and nickel. Measurement of the skin permeability to other substances than water is pertinent to the understanding of the influence of moisturizers on the skin permeability and, ultimately, to their therapeutic efficacy in the prevention of contact eczema due to exposure to harmful exogenous substances.

The aim of this study was to evaluate the effect of a moisturizer containing urea on allergic contact dermatitis. Twenty-five nickel-sensitized patients and five controls (non-sensitized volunteers) applied such a moisturizer on the volar side of one forearm twice daily for 20 days, while the other forearm served as the control. After treatment with the moisturizer, patch tests with 0%, 0.5% and 2% NiSO4 in petrolatum were applied in a randomized manner on each arm. After 72 h, the skin reactions were blindly evaluated by clinical scoring and by measuring transepidermal water loss and electrical impedance. After treatment, the baseline transepidermal water loss values were lower and the baseline magnitude impedance index values were higher on the pretreated forearm. According to clinical scoring and measurements with the two physical measurement techniques, the degree of the patch test reactions was equal. All control subjects had negative nickel tests. We concluded that the skin reactivity to nickel in nickel-sensitized patients is not significantly affected by use of the urea-containing moisturizer.

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.