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.     

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.     

Nonanoic acid--an experimental irritant

Irritant contact dermatitis is defined as a non-immunological skin reaction following exposure to various chemical, mechanical and physical factors. It is known that the skin response to irritants depends on the irritant applied and differs between chemically different irritants. Sodium lauryl sulfate (SLS) is an anionic detergent and the most frequently used substance in experimental irritant contact dermatitis. In 1980, it was suggested that nonanoic acid (NNA) could be used as a positive control when patch testing. Since then, NNA has been used as an experimental irritant in several studies and has been used as a chemically different substance compared to SLS. The present article presents a review of the application of NNA in studies on skin irritancy and experimental irritant contact dermatitis.     

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.     

Measurement of oedema in irritant-exposed skin by a dielectric technique

BACKGROUND: Easily applicable water-specific instruments measuring local oedema in skin are not available. The aim of this study is to demonstrate quantitative assessment of skin oedema with the dielectric technique by measuring increase of skin water content related to sodium lauryl sulphate (SLS)-induced irritant contact dermatitis. METHODS: Irritant skin reaction and resulting oedema were induced by an irritant patch test on volar forearms in 12 healthy volunteers with the application of 1% SLS for 6 h. After occlusion the volunteers were divided into two groups: the patch test site of group I (six volunteers) received no treatment other than a base cream for the skin reaction, while for group II (six volunteers) a strong corticosteroid (clobetasol propionate) was applied on the irritant skin. During a follow-up of 72 h, erythema was scored visually, and irritant-induced oedema was measured with a novel water-specific instrument MoistureMeter-D. RESULTS: In the untreated irritant skin, a maximum increase of 45% in skin water content was found at 10 h postocclusion and water content was still elevated at 72 h. With these persons, the degree of oedema agreed well with the ultrasound-measured skin thickness (P=0.053). In the corticosteroid-treated skin, an increase of 8% in water content was measured during 72 h but there was no correlation between oedema and skin thickness. There was no correlation between erythema and oedema in untreated or corticosteroid-treated skin. CONCLUSION: The new instrument can easily be applied for noninvasive quantitative evaluation of local oedema and fluid retention in irritant-exposed skin.     

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.     

Sodium lauryl sulphate penetration in an in vitro model using human skin

Because of their ability to impair the skin barrier function, detergents constitute a major risk factor for the development of irritant contact dermatitis. Sodium lauryl sulphate (SLS) is a commonly used detergent for experimental studies within the area of irritant contact dermatitis. In the present study, penetration of S³⁵-labelled SLS was studied in an in vitro model using human cadaver skin. The investigations showed that SLS is capable of permeating the skin barrier when applied under occlusion. SLS could be detected in the dermis and the amount of SLS found here was shown to depend on the dose of SLS applied on the skin. Penetration of SLS continued after removal of the SLS applied as a patch test on the skin surface. Considerable inter-individual variation in the penetration of SLS was demonstrated between different donors.     

The tandem repeated irritation test: a new method to assess prevention of irritant combination damage to the skin

The effect of a protective cream was tested in a new tandem repeated irritation test with tandem application of 0.5% sodium lauryl sulphate (SLS) and undiluted toluene. The irritants were applied twice daily for 30 min to the ventral forearms of 20 volunteers. Irritant cutaneous reactions were quantified by a visual score, transepidermal water loss, chromametry and skin capacitance. Concurrent application of SLS/toluene induced stronger reactions than those caused by twice daily application of each irritant on its own. A protective effect of the protective cream was obtained against all treatment combinations and was significant for SLS/SLS (p < or = 0.01) and SLS/ toluene (p < or = 0.05). Our results indicate that the tandem repetitive irritation test has great potential in the evaluation of skin care products to prevent irritant contact dermatitis.     

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.     

Beneficial effects of a skin tolerance-tested moisturizing cream on the barrier function in experimentally-elicited irritant and allergic contact dermatitis

In experimentally-induced irritant (ICD) and allergic (ACD) contact dermatitis, an oil-in-water (o/w) cream was applied to investigate its effects on a disturbed barrier function compared to untreated physiological barrier repair. Transepidermal water loss (TEWL) measurements were performed. Before the start of the experiments, the skin tolerance of the cream was examined, revealing the non-irritating characteristics of the ingredients and the absence of any contact allergic patch test reaction. In the ICD study, sodium lauryl sulfate (SLS) patches were applied to the forearms of young female volunteers. Consequently, it was observed that repeated cream application (14 days, 2x/day) significantly improved the TEWL of SLS-damaged skin, leading to a complete recovery on day 15. In the ACD study, disruption of skin barrier function was obtained by a nickel-mediated contact allergy patch (CAP) test. The cream was then applied 2x/day for 4 consecutive days. Assessment of TEWL clearly showed that recovery of the disrupted skin significantly improved after cream application in comparison to untreated barrier repair.     

Improvement in skin barrier function in patients with atopic dermatitis after treatment with a moisturizing cream (Canoderm)

Patients with atopic skin show a defective barrier function both in rough and in clinically normal skin, with an increasing risk of developing contact dermatitis. Moisturizing creams are often used in the treatment of dry skin. The purpose of this study was to investigate the influence of treatment with a urea-containing moisturizer on the barrier properties of atopic skin. Fifteen patients with atopic dermatitis treated one of their forearms twice daily for 20 days with a moisturizing cream. Skin capacitance and transepidermal water loss (TEWL) were measured at the start of the study and after 10 and 20 days. On day 21 the skin was exposed to sodium lauryl sulphate (SLS) and on day 22 the irritant reaction was measured non-invasively. Skin capacitance was significantly increased by the treatment, indicating increased skin hydration. The water barrier function, as reflected by TEWL values, tended to improve (P = 0.07), and the skin susceptibility to SLS was significantly reduced, as measured by TEWL and superficial skin blood flow (P < 0.05). Thus, it seems that certain moisturizers could improve skin barrier function in atopics and reduce skin susceptibility to irritants. The mechanism and the clinical relevance need further investigation.     

Assessment of skin irritancy by 2 short tests compared to acute irritation induced by sodium lauryl sulfate

Irritant contact dermatitis is a very common disease that i. preventable by protective measures The development of screening methods to identify subject with increased susceptibility in irritants is essential in reduce the incidence of this disorder in the workplace On the outlook for such methods. 2 quick non-invasive tests for irritability of the skin were compared to reliable, but time-consuming, patch testing with sodium lauryl sulfate (SLS) In 20 healthy volunteers, 0.5% SLS was applied on the medial 1/3 of the forearm for 23 h in order to induce experimental irritant contact dermatitis. On the same part of the forearm, 3 concentrations of dimethylsulfoxide (DMSO) and a solution of 0.2 mol/1 NaOH were applied for 5 min. Assessment of skin irritability was made by visual scoring and measurement of transepidermal water loss. No correlation between the "Quick tests" and SLS patch testing was found, indicating that tests assess different mechanisms of irritation.     

Efficacy of corticosteroids in acute experimental irritant contact dermatitis?

Background/aims: Topical corticoids are used to treat irritant contact dermatitis (ICD) in humans. However, their clinical efficacy remains sub judice. This study was designed to assess the efficacy of low- and medium-potency corticosteroids on irritant dermatitis.
Methods: We induced an acute ICD via open application of sodium lauryl sulphate (SLS) on the hands of subjects. The dorsal side of hands was irritated with 10% SLS five times in one day. Once on day 1 and twice daily on days 2–5, 1% hydrocortisone, 0.1% betamethasone-17-valerate and vehicle cream (petrolatum) were applied subsequently. Visual grading, bioengineering techniques and squamometry were used to quantify skin response.
Results: Corticosteroids were found ineffective in treating the surfactant-induced irritant dermatitis when compared with the vehicle and with the untreated control.
Conclusion: The counterintuitive result (in a relatively realistic and robust model) should be interpreted with caution until verified with other irritants of varying physicochemical properties.     

Intra-individual variation of irritant threshold and relationship to transepidermal water loss measurement of skin irritation

Irritant susceptibility studies have used either visual assessment or transepidermal water loss (TEWL) to determine subject response. We have developed a visual assessment method which determines subject irritant threshold. We examined the relationship between sodium lauryl sulfate (SLS) irritant threshold and TEWL measurements from normal skin and SLS patch tests. 19 subjects were recruited. The irritant threshold of each subject was measured and TEWL measurements made from the applied SLS patch tests. Individuals with a lower irritant threshold (easily irritated skin) had elevated TEWL levels compared to those with higher thresholds. The irritant threshold test had a low intraindividual variation. This study showed that the 2 methods grouped patients in a similar manner. The variation seen may reflect the different outcomes measured: irritant threshold visually assesses the skin inflammatory response while TEWL measures skin barrier modification.     

Acute irritant contact dermatitis: recovery time in man

Our understanding of the details of the recovery time of acute irritant contact dermatitis (ICD) is limited. We examined skin reactivity to a model surfactant, sodium lauryl sulfate (SLS). on previous acute ICD and normal sites over time with visual grading and noninvasive instruments. Acute ICD was induced on the upper arms of 18 volunteers (aged 30 to 51 years) by occluded application of 1% SLS for 24 h. Previous ICD and normal sites were provoked by occluded application of 2% or 7.5% SLS 30 min daily 4 consecutive days. Skin reactivity was assessed daily by visual erythema scoring (VES), transepidermal water loss (TEWL), skin color reflectance (SCR) and electrical capacitance (EC). Skin function of previous ICD sites assessed, by VES, TEWL. SCR, and EC did not normalize until 2 weeks later: all parameters of previous ICD returned to normal after 3 weeks. While skin reactivity to 2% und 7.5% SLS showed no differences between previous ICD and normal sites at 4 weeks, differences of irritant reactivity especially 7,5% SLS between previous ICD and normal sites were significant at 3 weeks post-provocation. Our results demonstrate that irritation evaluated with irritant provocation was long-lasting, even though skin functional parameters assessed by various bioengineering instruments returned to normal. Complete recovery of skin function including irritability after acute ICD induced by 1% SLS was achieved approximately 4 weeks later. The date were generated with a model surfactant: it remains to be determined whether similar responses will be noted with chemicals of different physicochemical properties.     

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.     

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.     

A bioengineering study on the efficacy of a skin protectant lotion in preventing SLS-induced dermatitis

Background/aims: This study evaluated the efficacy of a dimethicone skin protectant lotion against sodium lauryl sulfate (SLS)-induced irritant contact dermatitis (ICD) by clinical visual grading and bioengineering techniques in 12 healthy humans.
Methods: The flexor aspects of both forearms of the subjects were used as test sites. Each test was duplicated to diminish the variations of the test sites. In a random order and a double-blind manner, two test sites were pretreated either with the testing protectant lotion or with its vehicle control prior to contact with SLS. Thirty minutes later, 0.2 ml of 0.5% SLS in a polypropylene chamber was applied to each pretreated site. One additional test site served as a positive control (without lotion), receiving the irritant only. After 24 h of exposure to the irritant, the chambers were removed. The efficacy of protective effect was determined by four parameters: visual scoring (VS), transepidermal water loss (TEWL), skin color ( a * value), and cutaneous blood flow volume (BFV). All test sites were assessed with the parameters daily for 5 days.
Results: The VS data showed a significant decrease on the site pretreated with protectant lotion in comparison with the SLS-only treated site ( P <0.01) and with the site pretreated with control vehicle ( P <0.05) (overall for 5 days). TEWL value was significantly decreased in comparison with the SLS-only treated site ( P =0.02 at day 2; P =0.008 at day 4; P =0.014 at day 5) and with the site pretreated with the control vehicle ( P <0.05) (day 2, 4 and 5). However, the BFV and a * values did not show a statistical difference between protectant lotion, vehicle, and SLS-only treated sites.
Conclusions: This study demonstrated that appropriate dimethicone skin protection products may provide certain benefits from surfactant ICD. The skin protectant lotion may be used to prevent ICD in home or work environments, where skin irritants may induce dermatitis or eczema.     

Animal model for assessment of skin irritancy

Irritant skin reactions from repeated open applications of low concentrations of sodium lauryl sulphate (SLS) have been studied macroscopically and microscopically in guinea pigs. After 3 applications daily for 3 days, 2% SLS aqueous solutions gave a naked eye assessment, increase in epidermal thickness and total dermal inflammatory cell response, which was greater than for a 1% SLS solution. The dermal inflammatory cell response was mainly mononuclear (lymphocytic) in nature. With the SLS reactions as control, various organic solvents were studied and ranked against the SLS reactions and internally. Trichlorethylene was the most irritant solvent, ranking as high as 2% SLS. Other chlorinated hydrocarbons and aromatic hydrocarbons tested caused irritant reactions. The alcohols and acetone gave no reaction. White spirit was as irritant as trichlorethylene. Thinners were less irritant, around the level of the 1% SLS control reaction. The 4-day experimental design is a convenient and suitable animal model for screening irritant potential, and provides information relevant to the pathogenesis of irritant contact reactions.     

Artificial disruption of skin barrier prior to irritant patch testing does not improve test design

BACKGROUND: Irritant patch testing is often performed as a 24- or 48-h occlusive patch test with low concentrations of sodium lauryl sulphate (SLS). OBJECTIVES: The aim of this study was to investigate potential ways to shorten this test procedure and obtain precise test results. PATIENTS AND METHODS: Thirty-six healthy volunteers underwent irritant patch testing with different pretreatments (PT) of the test fields. Occlusive test chambers were applied on the upper back with SLS 0.5%, 1%, 2% and 5% in large Finn Chambers(R). The patches were removed after 4 and 24 h, respectively, depending on the concentration used. Test fields were pretreated as follows: PT 0, field without any PT (control); PT 1, prick with lancet; PT 2, prick with test stamp; PT 3, scratch with lancet; PT 4, incision with standardized incision instrument (0.1-0.2 mm depth). Skin reactions were evaluated by transepidermal water loss (TEWL), skin erythema and skin hydration and as well by a visual score (VS) at 4, 24 and 72 h. RESULTS: Our data show an obvious distinction between PT 0-2 and PT 3-4 at all measurement methods. The average TEWL values with PT 3-4 were higher than those with PT 0-2, especially on the 4-h course. This distinction may derive from the shape and size of the skin impairment achieved by PT 3-4, leading to a mechanical barrier disruption. However, SLS may infiltrate directly into deeper skin layers supported by capillarity. Consequently, no or little penetration through the epidermis and interaction with its structures occurs, which is responsible for irritant skin reactions. The SLS dose in the upper skin layers is therefore lower at these PTs. The lower remaining dose of SLS also explains this distinction, especially for the VS. Additionally, there are presumed reactions in deeper layers of the epidermis and dermis at PT 3-4. CONCLUSIONS: In summary, all data suggest a different reaction pattern from the classical irritant response. Therefore, application without any PT seems to be best suited for irritancy skin testing, especially for visual assessment. PTs prior to irritant patch testing have been shown to be unjustifiable.