Fruit acids do not enhance sodium lauryl sulphate-induced cumulative irritant contact dermatitis in vivo

Combined exposure to different irritants in the workplace may lead to irritant contact dermatitis, which is the main type of occupational dermatitis among bakers and confectioners. Following previous work on "tandem irritation", a panel of healthy volunteers was exposed twice daily for 4 days to the organic fruit acids: citric, malic, and lactic acid, either alone or in tandem application with 0.5% sodium lauryl sulphate (SLS) in a repetitive irritation test. Irritant cutaneous reactions were quantified by visual scoring and non-invasive measurement of transepidermal water loss and skin colour reflectance. Twice daily application of either citric or malic acid alone did not induce a significant irritant reaction. Combined exposure to one of the fruit acids and SLS caused marked barrier disturbance, but the latter irritant effect was smaller than that obtained by combined exposure to SLS and water. Thus, combined exposure to the above-mentioned fruit acids and SLS did not enhance cumulative skin irritation.     

Experimental irritant contact dermatitis due to cumulative epicutaneous exposure to sodium lauryl sulphate and toluene: single and concurrent application

In clinical practice, cutaneous exposure to a variety of irritants such as surfactants and solvents is frequent. Although the induction of irritant dermatitis by single irritants has been extensively studied in recent years, our knowledge of the effects of simultaneous application of different irritants is limited. Using non-invasive techniques for measurements of transepidermal water loss (TEWL) and skin colour reflectance, we quantified the irritant effects of single and concurrent application of 0.5% sodium lauryl sulphate (SLS) and undiluted toluene (TOL) in vivo. The irritants were applied twice daily for 30 min to the volar forearms of 20 volunteers. Repeated application of SLS and TOL induced an irritant reaction, as indicated by an increase in TEWL and skin redness. In contrast to SLS alone, the application of TOL alone induced only a moderate increase in TEWL, confirming previous results. Concurrent application of SLS/TOL and TOL/SLS induced significantly stronger reactions than those caused by twice daily application of each irritant on its own. Our results demonstrate that a mixed application of an anionic detergent and an organic solvent has an additive effect on skin irritation. It is suggested that pretreatment with SLS causes an increased susceptibility to TOL irritation and vice versa. Thus, the necessity for special precautions against skin absorption of TOL when handling detergents such as SLS is emphasized.     

Multicentre study for the development of an in vivo model to evaluate the influence of topical formulations on irritation

Although skin protective products to prevent irritant skin reactions are in wide use, neither standardized test models to prove differences in efficacy exist, nor has the quality or the reproducibility of results been evaluated in a multicentre approach. This should be mandatory when developing or testing skin care products. Therefore, we have designed a multicentre study in an approach to find a standardized test procedure for the evaluation of skin protective products. In this irritation study, a repeated short-time occlusive irritation test (ROIT) with a standardized protocol has been evaluated in 2 phases (12 days and 5 days protocol) in 4 (n=20) respectively 6 (n=33) skilled centres. The skin reaction was induced by 2 irritants (0.5% aq. SLS and toluene, 2x a day for 30 min). Its modification by 3 different cream bases with different hydrophilicity was analyzed. The irritation was monitored by bioengineering methods (TEWL measurement, colorimetry) and by clinical scoring. The evaluation showed that significant results could already be achieved with the 5-day protocol. Furthermore, in spite of the expected inter-centre variations due to heterogeneity of the individual threshold of irritation, interpretation of clinical score, and inter-instrumental variability, the ranking of the vehicles regarding reduction of the irritant reaction was consistent in all centres.     

Sequential application of cold and sodium lauryl sulphate decreases irritation and barrier disruption in vivo in humans

BACKGROUND: Irritant contact dermatitis (ICD) is one of the most frequent types of occupational dermatitis. Different factors are involved in the development of contact dermatitis. In the food-processing industry, the combined exposure to different irritants may be involved in the development of ICD. Few data have been published regarding the irritant potential of sodium lauryl sulphate (SLS) in combination with cold. OBJECTIVES: The present study was intended to analyse whether cold exposure and low skin temperature influence the development of ICD. METHODS: Twenty (part I) and 12 (part II) healthy volunteers were exposed twice daily for 4 days to SLS alone, different low temperatures alone (4 degrees C six times for 90 s with an interval of 20 s or 15 degrees C for 10 min) or a combination of cold and SLS (19.6 microL SLS 1% cm(-2), part I; or 52.6 microL SLS 0.5% cm(-2), part II) using the tandem repetitive irritation test. Irritant cutaneous reactions were measured by noninvasive biophysical methods with transepidermal water loss as a parameter for permeability barrier function and skin colour reflectance together with visual scoring as parameters for inflammatory reactions. RESULTS: Cold alone caused no significant skin reaction compared with untreated control. Exposure to SLS alone and SLS together with cold (independent of the applied temperature of 4 or 15 degrees C) twice daily induced a clear irritant reaction and barrier disturbance. Reactions did not differ whether SLS was applied before or after cold. Furthermore, 'tandem application' of cold and SLS diminished the barrier disruption and irritant reaction compared with SLS alone. CONCLUSIONS: We conclude that the application of cold may have a protective effect on the development of ICD, at least in our short-term model.     

Barrier recovery and influence of irritant stimuli in skin treated with a moisturizing cream

Moisturizers are used daily by many people to alleviate symptoms of clinically and subjectively dry skin. Recent studies suggest that certain ingredients in creams may accelerate the recovery of a disrupted barrier and decrease the skin susceptibility to irritant stimuli. In the present single-blind study, a moisturizing cream was tested for its influence both on barrier recovery in surfuctant-damaged skin and on the susceptibility of normal skin to exposure to the irritant sodium lauryl sulphate (SLS). Parameters measured were transepidermal water loss (TEWL) and skin corneometer values, indicating degree of hydration. Treatment of surfactant-damaged skin with the test cream for 14 days promoted barrier recovery, as observed as a decrease in TEWL. Skin corneometer values also normalized more rapidly during the treatment. In normal skin, use or the test cream significantly reduced TFWL after 14 days of treatment, and irritant reactions to SLS were, significantly decreased. Skin corneometer values increased after only 1 application and remained elevated after 14 days. In conclusion, the accelerated rate of recovery of surfactant-damaged skin and the lower degree of SLS-induced irritation in normal skin treated with the test cream may be of clinical relevance in attempts to reduce contact dermatitis due to irritant stimuli.     

The hairless guinea-pig as a model for treatment of cumulative irritation in humans

BACKGROUND: The effect of six skin-care formulations (SCFs) on experimentally induced cumulative irritation was studied in hairless guinea-pigs (HLGPs) and in human volunteers (HVs). The formulations were a basic cream, a carbomer cream and four modifications of the carbomer cream, containing either 10% isopropyl palmitate (IPP cream), 10% glycerol (glycerol cream), 19.5% canola oil (canola oil cream) or 0.5% (-)-alpha-bisabolol (bisabolol cream). METHODS: In HLGP, irritant dermatitis was induced with 30 min daily exposure for 4 days to 0.5% sodium lauryl sulfate aq. (SLS). In HVs, irritant dermatitis was induced with 10 min daily exposure for 5+4 days (no irritation on weekends) to 3% SLS aq. on the right and 30% nonanoic acid (NON) in n-propanol on the left volar forearm. Clinical scoring was performed daily; evaporimetry (total epidermal water loss (TEWL)), hydration and colorimetry were measured at baseline (day 0) in the middle and at the end of treatment. Treatments were applied twice daily. The basic cream and the IPP cream were excluded from testing in HLGP because they were known from previous studies to be irritant in HLGP, while all formulations were known to be equally and well tolerated locally in humans. RESULTS: All formulations worsened the skin irritation in HLGP: the glycerol cream the least, the canola oil cream the most, while the bisabolol cream and the carbomer cream were indistinguishable. In humans, the glycerol cream was better than 'No Treatment' after cumulative irritation with both SLS and NON. The basic cream was better tolerated in humans than was expected from previous testing in HLGPs. CONCLUSION: In conclusion, the results from the studies in HLGPs and HVs are in agreement with regard to ranking of the SCFs. Further, the glycerol cream showed a positive treatment effect on both SLS- and NON-irritated skin in HVs.     

Effects of disinfectants and detergents on skin irritation

We investigated the biological response of regular human skin to alcohol-based disinfectants and detergents in a repetitive test design. Using non-invasive diagnostic tools such as transepidermal water loss, laser-Doppler flowmetry and corneometry, we quantified the irritative effects of a propanol-based hand disinfectant (Sterillium), its propanol mixture (2-propanol 45% w/w and 1-propanol 30% w/w), sodium lauryl sulfate (SLS) 0.5% and distilled water. The substances were applied in a 2-D patch test in a repetitive occlusive test design to the back. Additionally, we performed a wash test on the forearms that was supposed to mimic the skin affection in the normal daily routine of health care workers. In this controlled half-side test design, we included the single application of the hand rub, SLS 0.5% and water as well as a tandem application of the same substances. Patch test and wash test showed similar results. The alcohol-based test preparations showed minimal irritation rather comparable to the application of water. However, the detergent SLS produced stronger barrier disruption, erythema and dryness than the alcohol-based preparations. There was no additional irritation at the combined use of SLS and disinfectants. By contrary, there was even a decrease in barrier disruption and erythema induced by the tandem application of SLS followed by alcohol-based disinfection compared with the use of SLS alone. These findings show a less irritant effect of alcohol-based disinfectants on the skin than detergents. Our study shows that there is no summation of irritating effects of a common detergent and propanol and that the combination of washing and disinfection has a rather protective aspect compared with washing alone.     

Fruit acids and sodium hydroxide in the food industry and their combined effect with sodium lauryl sulphate: controlled in vivo tandem irritation study

BACKGROUND: Cutaneous exposure to a variety of irritants has been extensively studied in recent years. Nevertheless, knowledge of the induction of irritant dermatitis, especially by mild irritants at low doses and for a short duration of exposure, is still incomplete. OBJECTIVES: To quantify the irritant effects and barrier disruption properties of ascorbic acid (ASC), acetic acid (ACA) and sodium hydroxide (NaOH), particularly in combination with an anionic detergent, sodium lauryl sulphate (SLS). METHODS: In a tandem repeated irritation test, the irritants were applied for 30 min twice daily for 4 days to the skin of the mid-back of 19 healthy volunteers of both sexes. We used bioengineering techniques for measurement of transepidermal water loss (TEWL) and skin colour reflectance, as well as visual scoring. RESULTS: Repeated application of ASC and ACA caused a moderate increase in TEWL and erythema. The sequential application of ASC or ACA and SLS enhanced these effects. NaOH induced a strong reaction when applied both occlusively and nonocclusively as well as in combination with SLS, with an early onset of the inflammatory signs, leading to discontinuation of the application on the third day in most of the test fields. Notably, the irritant effect of NaOH was not as marked when applied sequentially with SLS. CONCLUSIONS: Our results demonstrate that concurrent application of an anionic detergent and a mild acidic irritant can lead to disruption of the barrier function which, although not additive, is still considerable. The combined application of SLS and mild acids does not prevent SLS-induced irritation. Furthermore, we showed that NaOH in low concentrations may also act as a potent irritant but that its effect is not enhanced by SLS. The necessity of adequate skin protection and reduction of contact with substances that are potentially barrier disruptive and irritant, e.g. in the food industry, is emphasized, not only when handling detergents, but also when processing food products.     

Tacrolimus enhances irritation in a 5-day human irritancy in vivo model

Tacrolimus (FK 506) is a macrolide discovered in 1984 as a metabolic product of Streptomyces tsukabaensis. It has been used successfully in treating atopic dermatitis, allergic contact dermatitis, lichen planus mucosae and pyoderma gangrenosum. In the present study, we evaluated the anti-inflammatory activity of FK 506 in 2 human skin inflammation models. FK 506 as Protopic(R) cream was tested (i) in a 4-day repetitive irritation test with 2 x daily application of sodium lauryl sulphate (SLS), and (ii) in a UVB erythema model. The effect was evaluated visually and quantified by non-invasive bioengineering methods, namely chromametry and tewametry (TEWL). When FK 506 was applied 30 min after SLS irritation, an increased inflammation in comparison to controls was observed with all 3 methods, with only the TEWL data reaching statistical significance. 1 x daily application of FK 506 for 5 days, starting at the end of the 4-day irritation period, was without any effect. Similarly, no effect of FK 506 was seen in the UVB model. In conclusion, FK 506 was shown to enhance experimentally induced irritant contact dermatitis and not to accelerate healing of irritant contact dermatitis and UVB erythema.     

Invasive and non-invasive studies of the protective action of a silicon-containing cream and its excipient in skin irritation induced by sodium laurylsulfate

The purpose of our study was to evaluate the protective effect of a new silicone-containing barrier-cream (Anthydro) and its vehicle (Anthydro without silicone) in the prevention of cutaneous irritation by detergents. We therefore planned a study in several stages, using an anionic surfactant well known for its irritant properties: sodium laurylsulphate (SLS) in aqueous solution. In a first series of experiments, the protective effect of the Anthydro cream against SLS was studied by invasive methods on guinea-pigs in order to determine histologically the protective effect of the cream when a 10 p. 100 SLS solution was applied on the skin under occlusion during 24 hours (Square chambers, Van der Bend). Typical and reproducible lesions were apparent, and the protected sites were compared with the unprotected sites. In parallel, we used non-invasive methods (conductivity, transepidermal water loss and cutaneous blood flow) to determine in humans the protective effect of Anthydro cream in comparison with unprotected sites after application during 24 hours of patches soaked with a 5 p. 100 SLS solution on the forearms of 13 adult and healthy volunteers (Silver patch tests, Van der Bend). In both experiments the Anthydro cream was effective in reducing the SLS-induced cutaneous irritation. In a second series of experiments, the Anthydro barrier-cream was compared with its "base" (Anthydro without silicone) in terms of effectiveness, following the same experimental procedure (invasive on guinea-pigs, and non-invasive on humans). The base was shown to be effective in protecting against irritation. However, the histological lesions were less intense when the skin was protected by Anthydro than by its vehicle. Concerning the non-invasive methods in humans, no significant statistical differences appeared in the measurement of various parameters between the sites protected by Anthydro and the sites protected by the vehicle. These results lead us to suggest the existence of an essentially mechanical protective effect in which the silicone plays a very small part in terms of effectiveness. These experimental results necessitates further investigations to be extrapolated to occupational conditions without tests performed in industries and well-conducted epidemiological investigations.     

Bioengineering measurements of barrier creams efficacy against toluene and NaOH in an in vivo single irritation test

Background/aims: By now, only a few models have been published with the goal of testing barrier creams in vivo in humans. The aim of this study was to evaluate with a single irritation test, barriers creams in humans against a lipophilic and a hydrophilic irritant, toluene and NaOH, respectively.
Methods: Both irritants were applied for 15 min after pretreatment of the skin with barrier creams. Non-invasive bioengineering methods, such as skin colorimetry (a*) and cutaneous blood flow (CBF) measurements were used to assess product protection.
Results: After toluene application on control sites, the irritation appeared quickly (T_max=3 min after patch removal), was significant (+5-6 units for a* and+80% for CBF) and did not return to base value within 1 h. Skin irritation after NaOH application, as measured by a*, was less important (+2 units) and occurred later ( T "max=40 min after patch removal). For this irritant, CBF response was minor and variable. When testing barrier properties of the products, none of them were able to prevent the skin erythema induced by toluene. Against NaOH, one barrier cream as well as petrolatum and a fatty cream protected the skin significantly.
Conclusion: The present study points out the unsatisfactory effectiveness of several commercially available barrier creams claimed to protect against lipophilic or hydrophilic irritants.     

Post-application occlusion substantially increases the irritant response of the skin to repeated short-term sodium lauryl sulfate (SLS) exposure

Occlusion often, but not always, enhances percutaneous absorption and thus may facilitate skin irritation. Quantitative data about the impact occlusivity may have on minimal irritant stimuli to which the skin is exposed in daily life, and which may lead to chronic irritant contact dermatitis, are however lacking. Irritant stimuli were administered by repeated application of sodium lauryl sulfate (SLS) in an open application procedure. After the open exposure, the skin was either left open or occluded with plastic. Skin irritancy was assessed by means of visual grading and by transepidermal water loss (TEWL) measurements. Post-exposure occlusive treatment markedly enhanced the irritant response. 5 consecutive daily applications produced more irritation, with or without occlusion, than alternate day application. Occlusion may be a relevant factor in the development of irritant contact dermatitis from certain chemicals.     

Air flow at different temperatures increases sodium lauryl sulphate-induced barrier disruption and irritation in vivo

BACKGROUND: Combined exposure to dry climatic conditions and local heat sources together with detergents represents a common workplace situation. These conditions may support the induction of chronic barrier disruption leading subsequently to irritant contact dermatitis (ICD). OBJECTIVES: To test the irritant and barrier disrupting properties of air flow at different temperatures and velocities. METHODS: Using noninvasive biophysical measurements such as transepidermal water loss (TEWL) (TM 210; Courage & Khazaka, Cologne, Germany) we assessed the effects of short-term exposure to air flow at different temperatures (24 degrees C and 43 degrees C) in combination with sodium lauryl sulphate (SLS) 0.5% on the skin of 20 healthy volunteers in a tandem repeated irritation test. Chromametry was used to control the accuracy of the SLS irritation model. RESULTS: In our study air flow alone did not lead to a significant increase in TEWL values. Sequential treatment with air flow and SLS led to an impairment of barrier function and irritation stronger than that produced by SLS alone. The two different air flow temperatures led to different skin temperatures but had no influence on permeability barrier function. CONCLUSIONS: Warm air flow has an additional effect on the SLS-induced barrier disruption in a tandem irritation test with sequential exposure to SLS/air flow. This combination is suspected to promote ICD in workplace and household situations, especially in short-term applications as tested in our model.     

Additive impairment of the barrier function by mechanical irritation, occlusion and sodium lauryl sulphate in vivo

BACKGROUND: The interaction between potential irritants in the workplace might be important because workers are not usually exposed to a single irritant, but to multiple potentially harmful substances. Physical irritant contact dermatitis caused by friction or mechanical abrasion is a common occupational dermatosis. Prolonged water exposure by occlusion is also common in the workplace. Several studies have revealed the negative effect of the common anionic detergent sodium lauryl sulphate (SLS) on permeability barrier function. OBJECTIVES: To study the additive impairment of permeability barrier function by mechanical irritation combined with 0.5% SLS or prolonged water exposure by occlusion, as models of mild irritation. METHODS: The volar forearms of 20 healthy volunteers were exposed to mechanical irritation and occlusion with water or 0.5% SLS for four consecutive days in a combined tandem repeated irritation test (TRIT). Permeability barrier function was measured with a Tewameter TM 210. Irritation was assessed with a Chromameter CR 300 and a visual score. RESULTS: Barrier disruption in our model was rated as follows: occlusion with SLS and mechanical irritation > occlusion with SLS > occlusion with water and mechanical irritation > mechanical irritation and occlusion with water > occlusion with a glove and mechanical irritation > mechanical irritation > occlusion with water. Barrier disruption caused by occlusion or mechanical irritation was enhanced by the tandem application. The choice of irritant under occlusion, time of occlusion and order of tandem application all affected the degree of barrier disruption. Evaporimetry was able to detect early stages in the development of an irritant reaction before it became visible. Chromametry was not able to detect this early response. CONCLUSIONS: Physical irritants (friction, abrasive grains, occlusion) and detergents such as SLS represent a significant irritation risk and should be minimized, especially when acting together, as shown in our TRIT model.     

Tandem repeated irritation in aged skin induces distinct barrier perturbation and cytokine profile in vivo

Background The barrier perturbation pattern and molecular markers of inflammation upon tandem repeated irritation in chronologically aged skin have not been previously studied. Objectives We aimed to investigate the barrier impairment kinetic and in vivo cytokine profile following sequential irritation with sodium lauryl sulfate (SLS) and undiluted toluene (Tol) in aged compared with young skin. Methods Four fields on the volar forearm of healthy aged and young volunteers (median age, respectively, 63·9 and 32·6 years) were sequentially exposed to 0·5% SLS and undiluted toluene in a controlled tandem repeated irritation test; an adjacent nontreated field served as control. The permeability barrier function was monitored by repeated measurements of transepidermal water loss (TEWL), capacitance and erythema every 24 h up to 96 h. The stratum corneum cytokines were harvested by sequential tape stripping and quantified by multiplex bead array and enzyme‐linked immunosorbent assay. Results Compared with young skin, aged skin was characterized by delayed and/or less pronounced alterations in the visual irritation score, TEWL, chromametry a*‐value and capacitance, assessed by the respective Δ‐values for each parameter and monitoring time point. In both groups, exposure to SLS/SLS, SLS/Tol and Tol/SLS resulted in decreased interleukin (IL)‐1α levels, whereas the application of Tol/Tol induced an increase in IL‐1α. Furthermore, decreased IL‐1 receptor antagonist (IL‐1RA) levels and a lower IL‐1RA/IL‐1α ratio were found following repeated exposure to the irritants. Conclusions Our results provide evidence for selective alterations in the cytokine profile and distinct barrier impairment kinetic following tandem repeated irritation with SLS and Tol in aged compared with young skin in vivo.     

Efficacy of 4 commercially available protective creams in the repetitive irritation test (RIT)

Protective creams (PCs) play their part in the prevention of occupational contact dermatitis, even though efficacy data are frequently lacking. 4 different commercially-available PCs were evaluated against a set of 4 standard irritants (10%, sodium lauryl sulfate (SLS) 1% sodium hydroxide (NaOH), 30% lactic acid (LA) and undiluted toluene (TOL) in the repetitive irritation test (RIT) in humans described by Frosch and Kurte. 20 subjects were tested on the paravertebral skin on the mid-back. Irritation was assessed by visual scoring, transepidermal water loss (TEWL) as an indicator of epidermal barrier function, and colorimetry as a parameter of inflammation. Very different protective effects of the PCs on irritation by chemical substances were detectable. All products were very effective against SLS irritation. No PC provided significant protection against toluene. 3 products showed a partially protective effect against all ionic irritants, while the 4ih showed less protection against SLS and NaOH, and even amplification of inflammation by TOL. Considering the range of PC effects from good protection 10 increased irritation, depending on the irritant, the need for careful selection of PCs for specific workplaces is stressed.     

Metallothionein I and II gene knock-out mice exhibit reduced tolerance to 24-h sodium lauryl sulphate patch testing

BACKGROUND: Metallothioneins (MTs) are a group of proteins widely distributed in tissues regulating metal metabolism, scavenging free radicals, and taking part in immunological reactions. Knockout mice for MT genes I and II (MT(-/-)) exhibit reduced tolerance to ultraviolet B injury in vivo. Upregulation of MT proteins can be found at positive allergy patch-test sites; however, the role of MTs in skin irritation has not been investigated. AIM: To evaluate the role of MT genes in sodium lauryl sulphate (SLS)-induced skin irritation. SLS is a well-known model irritant in the study of experimental irritant contact dermatitis. METHODS: Skin irritation was induced in mice by applying closed-patch testing of 2.5%, 5%, 7.5% and 10% SLS in distilled water on the right dorsal skin of MT(-/-) mice for 24 h. Skin irritation was evaluated visually and by the number of infiltrated inflammatory cells in SLS-irritated skin. Homozygous wild-type mice with intact MT genes (MT(+/+)) tested at the same time served as controls. RESULTS: MT(-/-) mice showed a much higher degree of skin inflammation than did MT(+/+) mice. Numbers of infiltrated inflammatory cells were 312.8 +/- 50.9 vs. 136.2 +/- 13.1 for 2.5%, 430.2 +/- 49.3 vs. 242.6 +/- 28.6 for 5%, 540.2 +/- 28.4 vs. 437.6 +/- 22.2 for 7.5%, and 690.6 +/- 31.0 vs. 559.0 +/- 37.8 for 10% SLS in MT(-/-) and MT(+/+) mice, respectively (P < 0.05, Mann-Whitney U test). CONCLUSIONS: These results clearly suggest that the MTI and MTII genes may play an important protective role in SLS irritation. It would be valuable to study whether topical MTs can prevent or treat skin irritation.     

The hairless guinea-pig as a model for treatment of acute irritation in humans

BACKGROUND: The effect of six skin care formulations on experimentally induced acute irritation was studied in hairless guinea-pigs (HLGP) and in human volunteers (HV). The formulations were a basic cream, a carbomer cream and four modifications of the carbomer cream, containing either 10% isopropyl palmitate (IPP cream), 10% glycerol (glycerol cream), 19.5% canola oil (canola oil cream) or 0.5% (-)-alpha-bisabolol (bisabolol cream). METHODS: Acute irritation was induced by occlusive tests with 1% sodium lauryl sulfate aq. in both HLGP and HV, and in HV also by using nonanoic acid in n-propanol (NON) 20%. The irritant reactions were treated twice daily with the formulations from the time of removal of the patches. Evaluation of skin irritation and efficacy of treatments was performed daily for 4 days using clinical scoring, evaporimetry (transepidermal water loss), hydration measurement and colorimetry. RESULTS: The glycerol cream was the only product showing effects potentially better than no treatment in HV. CONCLUSION: The HLGP was too sensitive an animal model as a predictor for effect in humans. There was no difference in efficacy of the formulations against the two different irritants in HV.     

Irritants in combination with a synergistic or additive effect on the skin response: an overview of tandem irritation studies

Sodium lauryl sulfate (SLS) has often been chosen as a model for irritant contact dermatitis (ICD) to study the effect of irritants in combination (1-14). Recently 'tandem', or sequential, exposures with SLS have been performed to study the mechanism of skin barrier impairment in ICD (1-6, 15). The assessment of reactions have been documented with visual scoring, transepidermal water loss (TEWL), skin colour reflectance measurements, skin blood flow; among which TEWL has been noted as the most sensitive value (16). The matched control groups were treated with either a single exposure to a single irritant or in tandem with the same irritant repeatedly. Synergistic and additive effects have been reported for various tandem pairs of irritants, however, the mechanism for both remains unclear. The results of tandem irritation studies were evaluated to define and investigate the responses produced and deduce a possible mechanism of action. Clinical ramifications, albeit complex, are discussed.     

Impact of glove occlusion on cumulative skin irritation with or without hand cleanser–comparison in an experimental repeated irritation model

Background. Irritant contact dermatitis remains a substantial problem in the food processing industries. Irritants that are weak by themselves, such as glove occlusion and mild detergents, could interact to produce contact dermatitis. Objectives. To model the irritant action of an antibacterial hand cleanser and glove occlusion, with sodium lauryl sulfate (SLS) as a positive control. The effects of a pre‐exposure cream and a post‐exposure cream were also investigated. Methods. A modified repeated short‐time occlusive irritation test with 20 healthy volunteers, and application of irritants over 4 days, with pre‐exposure and post‐exposure creams and overnight glove occlusion, was performed. The changes in transepidermal water loss (TEWL) served as a measure of the irritant damage to the epidermal barrier. Results. The antibacterial cleanser and the glove occlusion separately induced only minor increases in TEWL. When combined, the two showed a tandem effect, as the TEWL increase was significantly higher, and was similar to that seen with the positive control, SLS. The pre‐exposure and post‐exposure creams alone significantly mitigated the cumulative irritation, and this effect was strongest when the two creams were combined. Conclusions. Irritant contact dermatitis may develop through the tandem effects of long‐term glove occlusion and the accumulation of barrier damage from hand washing, even when mild hand cleansers are employed.