Irritant effects of a detergent in wash, chamber and repeated open application tests

Strong underwater adhesion of injectable hydrogels triggered by diffusion of small molecules

It is challenging for injectable hydrogels to achieve high underwater adhesiveness. Based on this concern, we report a fully physically crosslinked injectable hydrogel composed of gelatin, tea polyphenols and urea, capable of realising smart adhesion to various materials, like glass and porcine skin, in diverse aqueous environments. The urea molecules are designed as crosslinking disruptors for interfering with the formation of hydrogen bonds in the hydrogel, therefore modulating its crosslinking density and mechanical properties such as tensile strength, toughness and adhesive strength. Triggered by physical diffusion of the urea molecules towards the surrounding liquid environment, the hydrogel can achieve efficient (∼10 s), self-strengthening and long-lasting (>2 weeks) underwater adhesion. Remarkably, for fresh porcine skin, the instantaneous underwater adhesive strength is 10.4 kPa whereas the peak strength is as high as 152.9 kPa with the aid of the self-strengthening effect. More interestingly, it can simultaneously form controllable underwater non-adhesive surfaces, regulated by changes in the diffusion-triggered local concentration of urea. Further, it is also biocompatible, antibacterial, biodegradable and 3D printable in water, which offers great convenience for various applications concerning smart interfacial adhesion, like biomedicine and flexible electronics. Likewise, the physical diffusion-mediated mechanism represents an innovative strategy for developing next-generation smart hydrogels.

Increased Skin Irritation by Hydroquinone and Rsetinoic Acid Used in Combination

Background

Hydroquinone (HQ) is frequently combined with retinoic acid (RA) to enhance lightening efficacy, which may also affect skin irritancy. Although skin irritation leads to postinflammatory hyperpigmentation, little research has been performed to compare skin irritancy between each component and the combination.

Objective

This study was done to examine whether HQ-RA combination increased skin irritation induced by HQ or RA alone.

Methods

Patch testing was performed using maximum therapeutic and higher concentrations of HQ and RA in 10 volunteers, and then, it was performed using their popular therapeutic concentrations and combination in the other 20 volunteers. In vitro irritation was also assessed in primary cultured normal human keratinocytes treated with 80% and 50% cell survival doses of HQ, 80% cell survival dose of RA, and their combination.

Results

The combination in patch testing induced stronger erythema than the corresponding concentrations of HQ and RA, which was remarkable with use of combination of higher concentrations. In cultured keratinocytes, the RA combination significantly decreased cell viability, but increased cytotoxicity and extracellular interleukin 1 alpha release with corresponding doses of HQ.

Conclusion

The results of patch tests and in vitro irritation assessment tests suggested that HQ and RA increased skin irritation when used in combination.

In vivo studies of substances used in the cosmetic industry

Cosmetic producers are obliged to guarantee the safety and stability of their products. The current legal regulations are based on the European Union Directive (1223/2009) of 30 November 2009. The main aim of the directive is to formulate criteria of safety of a cosmetic product and requirements that it must meet to be placed on the market. A new cosmetic product is subjected to thorough investigation prior to its introduction on the market. It should be studied not only with respect to its safety, but also with respect to its effectiveness declared by the producer. The studies are performed in vivo, by the contact or epidermal patch tests on the human skin.

Efficacy and tolerability of oral lactoferrin supplementation in mild to moderate acne vulgaris: an exploratory study

OBJECTIVE

Lactoferrin, an innate defense iron-binding protein, possesses antimicrobial and anti-inflammatory activities. Beneficial systemic effects on inflammatory diseases have been proposed. The aim of the present study was to explore the efficacy and tolerability of oral bovine lactoferrin supplementation in subjects with mild to moderate facial acne vulgaris.

METHODS

In this open-label, single-arm study, 43 adolescents and young adults were enrolled to take a chewable tablet formulation of bovine lactoferrin twice daily for 8 weeks. The primary efficacy endpoint was the improvement in acne lesion counts compared with baseline. Tolerability was evaluated on the basis of adverse event frequencies.

RESULTS

Thirty-nine subjects, aged 17.5 ± 3.8 years, completed the study per protocol. At the end of the study (week 8), a mean reduction in inflammatory lesion count of 20.2% (-2.2 ± 7.0, p = 0.054), in non-inflammatory lesion count of 23.5% (-6.2 ± 9.8, p < 0.001), and in total lesion count of 22.5% (-8.4 ± 13.1, p < 0.001) was observed as compared with baseline. At study conclusion, 76.9% (30 of 39) of subjects showed a reduction in total lesion count. The results for inflammatory acne lesions were variable over the study course. None of the subjects experienced a lactoferrin-related adverse event during the trial.

CONCLUSION

Despite the limitations of an uncontrolled, open-label study, the results from this study indicate that lactoferrin in mild to moderate acne vulgaris is well tolerated and may lead to an overall improvement in acne lesion counts in the majority of affected adolescents and young adults when administered as a dietary supplement on a twice daily regimen. Further randomized, placebo-controlled trials of longer duration appear warranted.

Evaluation of the effect of Dardia Lipo Line on skin inflammation induced by surfactants using the repeated open-application test

BACKGROUND

Medical skin care products are topical preparations with mainly moisturizing properties. A new line of medical skin products with an excellent tolerability profile and improved hydration for dry skin has been developed, but beneficial effects have not yet been investigated on damaged skin.

AIM

To investigate if these products maintain barrier function and hydration status, improve subjective symptoms due to irritant contact dermatitis and to prove their tolerability on damaged skin.

DESIGN AND METHODS

Single-centre, blinded, randomized, controlled study in 20 healthy Caucasian women. 5% sodium lauryl sulphate solution was used to induce skin irritation. Two sites on the inside surface of both forearms of each subject were treated daily for 5 days (irritation period). Lipo Cream, Lipo Milk (water-in-oil emulsions) and Lipo Ointment (water-free formulation) were applied twice daily to three of the four test sites on days 1-5. The fourth site was used as a control. Visual readings, subjective symptom assessments, transepidermal water loss (TEWL) and colorimetric measurements, corneometry and skin microrelief macrophotographies were done on days 1-6.

RESULTS

On day 6, TEWL was increased vs baseline on all sites; however, TEWL with Lipo Cream or Lipo Ointment was significantly lower than control. At day 6, skin capacitance was 94%, 100% and 85% of baseline value for the cream, milk and ointment, respectively, versus 72% for control. All test products were well tolerated.

CONCLUSIONS

Lipo Line products showed both protective properties against epidermal dysfunction and significant hydrating effect.

Emollients in a propanol-based hand rub can significantly decrease irritant contact dermatitis

The objective of this study is to determine the effect of emollients in a propanol-based hand rub on skin dryness and erythema. In this prospective, randomized, controlled, double-blind trial, 35 subjects participated; of them approximately half were atopic (modified Erlanger atopy score > or =8). 2 propanol-based formulations were tested in a repeated open application test, 1 contained a mixture of emollients (0.81%, w/w). 2 aliquots of 0.7 ml of each formulation were applied twice per day over 2 weeks to the cubital fossa of each subject after random assignment of the preparations. Treatment areas were assessed before each application and 3 days postfinal application by visual inspection for erythema and dryness according to a standard scale. The sum score over all assessment time-points served as primary parameter. The mean sum score for erythema and dryness was significantly lower for the hand rub with emollients (0.8 +/- 2.4) in comparison with that for the hand rub without emollients (1.5 +/- 3.5; P = 0.022; Wilcoxon signed rank test). A comparison of the atopic and non-atopic subjects revealed no significant difference for any of the products (P > 0.05; Mann-Whitney U-test). It is concluded that the addition of emollients to a propanol-based hand rub can significantly decrease irritant contact dermatitis under frequent-use conditions.

Skin reaction and recovery: a repeated sodium lauryl sulphate patch test vs. a 24-h patch test and tape stripping

BACKGROUND

Little is known of the predictive value of methods to test an individual's susceptibility to acquiring occupational contact dermatitis. Recently, the recovery rate after induced irritation was suggested for this purpose. Although it is likely that repeated exposure to sodium lauryl sulphate (SLS) is preferable to a single application, there is little evidence to support this idea. Similarly, little is known about whether the outcome of a repeated SLS test can be predicted by a brief test.

OBJECTIVES

We studied the relationship between the skin reaction after a repeated SLS test and two brief tests, devoting special attention to the recovery rate.

METHODS

In 29 healthy volunteers, we measured transepidermal water loss (TEWL) and erythema after applying 0.03, 0.1 and 0.3% SLS for 6 h, 3 days per week, over a course of 3 weeks. The data were compared with the effects after applying 0.1, 0.3 and 1.0% SLS for 24 h and with 10 and 15 repetitions of tape stripping.

RESULTS

A poor correlation was found between the repeated test and the brief SLS test, or tape stripping, when using an increase in TEWL (r = 0.04 and 0.26, respectively) or its recovery rate (r = - 0.01 and 0.42, respectively).

CONCLUSIONS

We presume that in a repeated test of sufficient duration, additional mechanisms come into play that are absent in a brief test, e.g. an alteration in the thickness of the epidermis, with a resulting change in the permeability of SLS. When such an effect differs between subjects it could explain the lack of agreement between the acute and the repeated tests. At present, a brief irritation test will, in all likelihood, be unable to assess an individual's susceptibility to occupational contact dermatitis.

Non-animal testing strategies for assessment of the skin corrosion and skin irritation potential of ingredients and finished products

The dermatotoxicologist today is faced with a dilemma. Protection of workers and consumers from skin toxicities (irritation and allergy) associated with exposure to products, and the ingredients they contain, requires toxicological skin testing prior to manufacture, transport, or marketing. Testing for skin corrosion or irritation has traditionally been conducted in animals, particularly in rabbits via the long established Draize test method. However, this procedure, among others, has been subject to criticism, both for its limited predictive capacity for human toxicity, as well as for its use of animals. In fact, legislation is pending in the European Union which would ban the sale of cosmetic products, the ingredients of which have been tested in animals. These considerations, and advancements in both in vitro skin biology and clinical testing, have helped drive an intensive effort among skin scientists to develop alternative test methods based either on in vitro test systems (e.g. using rat, pig or human skin ex vivo, or reconstructed human skin models) or ethical clinical approaches (human volunteer studies). Tools are now in place today to enable a thorough skin corrosion and irritation assessment of new ingredients and products without the need to test in animals. Herein, we describe general testing strategies and new test methods for the assessment of skin corrosion and irritation. The methods described, and utilized within industry today, provide a framework for the practicing toxicologist to support new product development initiatives through the use of reliable skin safety testing and risk assessment tools and strategies.

Effects of various grit-containing cleansers on skin barrier function

Products intended for individuals in contact with strongly adhering dirt often contain grit. Various clinical test methods have been developed for evaluating the potential of personal washing products to induce skin irritation. In the present study, differences in the irritant effects of washing products containing naturally-derived grit and synthetic grit were investigated in a forearm wash test. The forearms of 16 test subjects were washed in a total of 18 treatments (4 per day for 4 days, with 2 treatments on the 5th day). Treatment consisted of continuous washing for 2 min by a technician, who gently slid his fingertips with the lather up and down the forearm. Non-invasive instrumental measurements of skin barrier function were performed. Repetitive washing for 1 week lead to increased TEWL values, skin redness and decreased stratum corneum hydration. Results indicate differences in irritancy potential due to different types of grit, their surface and concentration. It is concluded that the repeated wash test seems to be adequate for rating personal washing products that contain grit.

Irritancy ranking of anionic detergents using one-time occlusive, repeated occlusive and repeated open tests

Discrepancies between the one-time patch test and the wash test regarding the ranking of irritancy of detergents have been found in the literature. The aim of the present study was to investigate the concordance of irritancy rank order of 4 anionic detergents tested by 3 different exposure methods, namely one-time occlusive, repeated short-time occlusive and repeated short-time open tests. These detergents were sodium cocoyl isethionate (ISE), sodium lauryl sulfate (SLS), soap and disodium lauryl 3-ethoxysulfosuccinate (SUC). The reactions were evaluated by visual scoring and by transepidermal water loss (TEWL) measurement. When scored visually, the rank order in the one-time test was: SOAP > or = SLS > or = ISE > SUC. The other test methods yielded a different order: SLS > ISE > or = SOAP > SUC. A similar rank order was obtained with TEWL measurement for all exposure methods. Generally, the concordance among the different exposure methods was high when evaluated by TEWL. The concordance was lower when evaluation was performed by visual scoring. The present study demonstrates that the choice of exposure model and evaluation method may be important variables influencing the outcome of irritancy testing. It is proposed that the repeated open test is the best way to simulate most in-use situations where the uncovered skin is exposed to detergents. The repeated occlusive test or the one-time patch test may be better to simulate situations in which the skin is occluded after irritation by detergents.