Evaluation of skin irritancy of sodium lauryl sulphate: a comparative study between the replica method and visual evaluation

Properties of pressure-sensitive adhesive tapes with soft adhesives to human skin and their mechanism

BACKGROUND/PURPOSE

The use of soft adhesives in the manufacture of pressure-sensitive adhesive tapes has recently increased. The dermal peeling force of adhesive tapes with soft adhesives was studied.

METHODS

Four kinds of adhesive tapes with adhesives of different softness were made, by adding varying amounts of isopropyl myristate as a softener. The tapes were applied on the flexor side of the forearm of six healthy male volunteers. The dermal peeling force, the amount of stripped corneocytes, the level of pain when the tapes were removed and the degree of penetration of adhesives into the sulcus cutis (skin furrows) were evaluated at 1 and 24 h after application of the tapes. Furthermore, a skin model panel (a sulcus cutis and crista cutis model panel) and a crista cutis model panel were constructed from a general stainless-steel panel, and the peeling force of the tapes against the model panels was measured.

RESULTS AND CONCLUSION

As the softness of adhesives increased, the peeling force against a general stainless-steel panel with a flat surface decreased, although the peeling force against human skin did not significantly change. The amount of stripped corneocytes on the removed tapes and the level of pain when the tapes were removed decreased with the increase in softness of the adhesives. These results suggest that adhesive tapes with soft adhesives that contain isopropyl myristate as a softener are suitable for the skin. Furthermore, the degree of penetration of adhesive into the sulcus cutis increased as the softness of adhesives increased. Upon evaluation of the peeling force against the model panels, as the softness of adhesives increased, there was a slight decrease in the peeling force against the skin model panel, while there was a remarkable decrease in the peeling force against the crista cutis model panel. These results suggest that the lack of change in the dermal peeling force as the softness of adhesives increased was caused by penetration of soft adhesive into the sulcus cutis, and that the decrease in the amount of stripped corneocytes was caused by a decrease in the peeling force against the crista cutis, which consists of corneocytes mainly removed by the tapes.

Objective evaluation for severity of atopic dermatitis by morphologic study of skin surface contours

BACKGROUND/AIMS

Wide variation in outcome methodology can make the interpretation of patient outcomes confusing and the comparison of the results of different studies almost impossible. It is important to objectively measure and record the severity of atopic dermatitis (AD) for routine clinical practice and research. The aim of this study was to evaluate whether morphologic study of skin surface contours might be helpful to objectively quantify the severity of AD.

METHODS

Thirty atopic patients (12 females, 18 males) participated in this study. Moisturizer was applied twice daily for 2 weeks. Bioengineering methods such as D-Squame, corneometer, evaporimeter, and spectrophotometer were measured at the start of the study and after 1 week and 2 weeks. In addition, we assessed moisturizer effects after 3 h of moisturizer application.The stereoimage optical topometer (SOT) based on a new concept of stereoimage was applied for this study. We compared SOT, other bioengineering methods, and the severity scoring of atopic dermatitis (SCORAD) index.

RESULTS

After 3 h of application with moisturizer, the results measured by SOT, conventional optical profilometer (COP), D-Squame, and corneometer showed significant differences (P<0.05). After 1 and 2 weeks, there were significant changes in the results measured by SOT, COP, D-Squame, corneometer, spectrophotometer, and SCORAD index. We observed a significant correlation between bioengineering methods and the SCORAD index (P<0.05).

CONCLUSION

These data indicate that morphologic study of skin surface contours are useful in evaluating of AD severity. If we would combine methods to evaluate the physiologic changes and those such as SOT to measure the morphological changes of skin surface, we could evaluate more objectively and quantitatively the severity of AD.

Skin irritation due to repetitive application of adhesive tape: the influence of adhesive strength and seasonal variability

BACKGROUND/PURPOSE

Influence of the repetitive application of pressure-sensitive adhesive tapes on skin was evaluated.

METHODS

Two kinds of tapes with different adhesive strengths were repetitively applied to the inside of the forearm of six volunteers in winter and summer, in order to examine the dermal peeling force, the amount of stripped corneocytes, transepidermal water loss (TEWL), hydration and deepened skin furrows (changes in skin surface topography) in the epidermal stratum corneum.

RESULTS AND CONCLUSION

As adhesive tapes were applied repetitively, dermal peeling force gradually increased while the amount of stripped corneocytes decreased. As the cumulative amount of stripped corneocytes increased with repetitive applications, the skin irritation worsened as measured by increased destruction of the skin surface topography and TEWL. These phenomena were more marked with the stronger adhesive tape, and there was seasonal variability.

Objective interpretation of severity of SLS induced edema by stereoimaging

BACKGROUND

In the evaluation of the severity of skin inflammations, visual scoring system is widely being used as a subjective method. However, it is well known that interobserver variations occur even between the interpretations of experienced dermatologists.

OBJECTIVE

To develop a new objective and quantitative method for the evaluation of skin surface contours and for the assessment of severity in SLS-induced edema, a new investigatory tool based on the concept of "stereoimaging" was studied. Differences between binocular images were used by a stereoimage optical topometer (SOT) system capable of calculating skin surface topographic information, which was then used to produce a three-dimensional image.

METHODS

We compared the results obtained by SOT with a visual scoring system after applying sodium lauryl sulfate (SLS) to skin. The degree of edema was assessed qualitatively by visual scoring (0: none, 1: mild edema, 2: moderate edema, 3: severe edema). To quantify the severity, five three-dimensional parameters (S(a), S(z), SL, SA and SV) were used in the SOT analysis.

RESULTS

The means of these five parameters increased significantly in visual grade 1+ compared to visual grade 0 and the means of the five parameters decreased significantly and proportionally as the visual grades increased from 1+ to 3+. A highly significant correlation was found to exist between the visual scoring results and the five SOT parameters.

CONCLUSION

SOT can be used to evaluate the severity of SLS-induced edema objectively and can be extensively applied to evaluate the degree of severity in other inflammatory skin conditions.

Latex allergy: past and present

Although latex products have been in use for over a century, allergic responses to latex proteins have only been recognized as a serious health problem for the past 15 years. Latex allergy particularly affects two groups, health care workers (HCW) and children with spina bifida (SB). This manuscript provides a brief history of latex allergy, and a review of the following: the manufacturing process for dipped latex products, the 11 latex allergens that have been characterized and received allergen designations by the International Union of Immunological Societies, the methods used in exposure assessment, the epidemiology and clinical management of latex allergy, and the use of animal models in investigating mechanisms underlying latex allergy.

Skin premature aging induced by tobacco smoking: the objective evidence of skin replica analysis

Epidemiological studies have showed that heavy smoking causes premature skin aging. Using a silicone rubber replica combined with computerized image processing, an objective measurement of skin's topography, we investigated the association between wrinkle formation and tobacco smoking in this study. The replica analysis was used to study the changes in the surface furrows of the volar forearm in 63 volunteers. Results confirmed that the depth (Rz) and variance (Rv) of furrows were increased and lines of furrows (Rl) were decreased with age. The replica analytic results showed that Rz and Rv in subjects with a smoking history > or =35 pack-years were significantly higher than non-smokers (P<0.05). Rl in subjects with a smoking history were significantly lower than non-smokers (P<0.05). In addition, the present results gave a good correlation between the parameters from the computerized replica analysis with the clinical grading assessment of wrinkles, which further confirmed that skin replica technique is an objective and efficacious tool in evaluation of skin premature aging.

Water disrupts stratum corneum lipid lamellae: damage is similar to surfactants

Using electron microscopy, we investigated the effect of (i) a dilute surfactant and of water alone on the ultrastructure of stratum corneum lipids in pig skin exposed in vitro at 46 degrees C, and (ii) of water alone on human skin exposed in vivo at ambient temperature. For pig skin, the surfactant sodium dodecyl sulfate disrupts stratum corneum intercellular lamellar bilayers, leading to bilayer delamination and "roll-up" in a water milieu after 1 h, extensive bilayer disruption after 6 h, and nearly complete dissociation of corneocytes after 24 h. Corneodesmosomes show progressive degradation with exposure time. Water alone also disrupts the stratum corneum, but with a slower onset. Alterations in intercellular lamellar bilayers, but not intercellular lamellar bilayer roll-up, are detected after 2 h. Intercellular lamellar bilayer roll-up occurs after 6 h. Extensive dissociation of corneocytes occurs after 24 h of water exposure. Unlike sodium dodecyl sulfate, water exposure results in the formation of amorphous intercellular lipid. Corneodesmosome degradation parallels intercellular lamellar bilayer disruption; calcium appears to offer some protection. Similar disruption of intercellular lamellar bilayers occurs in human skin in vivo at ambient temperature. Our studies show that water can directly disrupt the barrier lipids and are consistent with surfactant-induced intercellular lamellar bilayer disruption being due at least in part to the deleterious action of water. Intercellular lamellar bilayer disruption by water would be expected to enhance permeability and susceptibility to irritants; accordingly, increased attention should be given to the potential dangers of prolonged water contact. For common in vitro procedures, such as skin permeation studies or isolation of stratum corneum sheets, exposure to water should also be minimized.

Glove powder affects skin roughness, one parameter of skin irritation

Most patients with immediate-type-hypersensitivity to natural rubber latex (NRL) give a history of hand eczema. Susceptibility to allergens is increased by irritant hand eczema due to damage to the skin barrier. Therefore, especially for employees in medical or paramedical professions, reduction in skin irritation is of importance. The present study reports the effect of glove powder on skin roughness, one feature of skin irritancy. Skin replicas, performed before and after wearing different types of gloves, were evaluated by laser profilometry. Significant alteration of skin roughness was evident and determined by different factors. Use of unpowdered Biogel gloves on prepowdered hands results in an increase in skin roughness, in contrast to the use of Biogel gloves on hands without any pre-application. On the other hand, powdered Manex neoderm gloves show no influence on the skin structure, whereas powdered Peha taft gloves also increase the roughness of the skin. Other potential candidates causing skin morphology alteration could be the glove pH, rubber chemicals with irritant potential and other characteristics of gloves, which are already under investigation.

Reproducibility of a non-invasive skin irritancy test in a cohort of metalworker trainees

The identification of subjects with increased susceptibility to irritants may play an important rôle in the prevention of irritant contact dermatitis. A short and quick method of non-invasive testing for assessing irritant sensitivity was developed by Wilhelm and coworkers in 1990, based on the alkali resistance test of Burckhardt. In order to determine the reproducibility of this screening method, 204 healthy metalworker trainees were tested 2 x according to Wilhelm within an interval of 6 months. No statistically-significant correlation could be shown, indicating that the reproducibility of this screening method is low. Therefore, we propose applying not just a single test for the assessment of skin irritability, but a series of tests, in order to improve the reliability of this kind of testing.

Evaluation of a human patch test for the identification and classification of skin irritation potential

Current regulations require that the skin irritation/corrosion potential of new chemicals is assessed in the rabbit Draize test, although there are opportunities to use alternative methods to identify the most aggressive materials. Previously, we have proposed that it is possible to employ a strategy that avoids the use of animals and at the same time delivers a more relevant assessment of skin irritation/corrosion potential. The approach is to identify corrosive materials in vitro and then proceed to human volunteer testing for skin irritation. In this study, the human 4-h patch test, its interpretation, and results with 29 test materials are presented. Using 14 materials not classified as "Irritating to skin" by EU criteria, 13 classified as "Irritating to skin" by suppliers, and 2 as "Corrosive - causes burns", it is demonstrated that, by evaluating these on human skin in vitro and in vivo, a significant proportion are either over-classified or under-classified. In conclusion, we are convinced that by application of the approach described in detail here, it is possible to avoid the use of animals, whilst at the same time obtaining an assessment of skin irritation/corrosion potential that is more relevant to man, and which, if required, may be used directly for classification and labelling of substances and preparations within the European Union.

Evaluation of human skin irritation by carboxylic acids, alcohols, esters and aldehydes, with nitrocellulose-replica method and closed patch testing

Closed patch testing and the nitrocellulose-replica method are performed as useful clinical methods for the evaluation of human skin irritation by cosmetics and topical medicaments. Comparison of the sensitivity between microscopic scoring by nitrocellulose-replica method and visual scoring by closed patch test in the detection of skin irritation, however, has not been well studied with statistical analysis. Here, we evaluated human skin irritation by carboxylic acids, alcohols, esters and aldehydes, with different chain length (C8-C18), using both methods. The results of closed patch testing showed that, although the score of skin irritation for carboxylic acids (C8, C12), alcohols (C8) and aldehydes (C8), tested at a concentration of 0.5 m-2.0 m, significantly increased with increasing concentration of the test compounds, ester compounds scarcely caused any irritation on the surface of the skin occluded. In addition, an increase of carbon chain length in the test compounds made it impossible to detect skin irritation. In contrast, the nitrocellulose-replica method could evaluate skin reactions against very weak irritants that gave no macroscopic alterations on the skin surface in the closed patch test. However, the scoring system is somewhat subjective and should be improved to make the analysis more objective.

Effect of occlusion on human skin

In order to investigate the effect of occlusion on the skin, the flexor sides of both upper arms were covered with column-shaped with column-shaped closed chambers, 30 mm in outer diameter, 20 mm in inner diameter, and 5 mm in height, which were made of polyethylene foam. The tops of the chambers were sealed by plastic films with various levels of water vapor permeability to control moisture in each chamber. The raised chamber walls prevented direct contact between the skin and the plastic film. After 24 h of application, morphological changes of the skin surface were observed microscopically by the nitrocellulose-replica method. Although no visual alterations were found on all areas of occluded skin, microscopic evaluation showed that simple occlusion by films induced an increase in the number of deepened skin furrows on the skin surface. this increase was associated with lower water vapor permeability of the films, as well as with higher values of both temperature and humidity of the test day. Thus, since conditions which facilitate perspiration from the skin tend to cause skin irritation, prolonged exposure of the skin to sweat by simple occlusion may act as a primary skin irritant.