Hydroxyisohexyl 3-cyclohexene carboxaldehyde allergy: relationship between patch test and repeated open application test thresholds

Background  Hydroxyisohexyl 3-cyclohexene carboxaldehyde (HICC) is a synthetic fragrance ingredient. Case reports of allergy to HICC appeared in the 1980s, and HICC has recently been included in the European baseline series. Human elicitation dose–response studies performed with different allergens have shown a significant relationship between the patch-test threshold and the repeated open application test (ROAT) threshold, which mimics some real-life exposure situations. Fragrance ingredients are special as significant amounts of allergen may evaporate from the skin.
Objectives  The study aimed to investigate the relationship between elicitation threshold doses at the patch test and the ROAT, using HICC as the allergen. The expected evaporation rate was calculated.
Materials and methods  Seventeen HICC-allergic persons were tested with a dilution series of HICC in a patch test and a ROAT (duration up to 21 days). Seventeen persons with no HICC allergy were included as control group for the ROAT.
Results  The response frequency to the ROAT (in μg HICC cm⁻² per application) was significantly higher than the response frequency to the patch test at one of the tested doses. Furthermore the response rate to the accumulated ROAT dose was significantly lower at half of the doses compared with the patch test. The evaporation rate of HICC was calculated to be 72% over a 24-h period.
Conclusions  The ROAT threshold in dose per area per application is lower than the patch test threshold; furthermore the accumulated ROAT threshold is higher than the patch test threshold, which can probably be explained by the evaporation of HICC from the skin in the open test.     

FS04.4Decreased MDBGN conc. in a product is counteracted by increased exposure

Background:  Some types of cosmetic products such as creams and soaps are commonly used several times a day, especially in occupational use‐situations. Little is known about how the daily frequency of application of an allergen in a product influences the allergic response.
Objectives:  This study investigates the allergic responses elicited in pre‐sensitised individuals when exposed to a specific amount of allergen applied either in 1 application per day or distributed over 4 applications per day. As model allergen is used the cosmetic preservative methyldibromo glutaronitrile (MDBGN). Patients/Methods: 19 contact allergic individuals and 12 controls participated in a double‐blind, randomized repeated open application test (ROAT) using two coded aqua/ethanol (80:20) solutions preserved with 100 ppm and 400 ppm MDBGN, respectively. 12 cm² areas on the lower arms were applied 2 drops either once daily of the 400 ppm solution or 4 times a day for the 100 ppm solution.
Results:  Most patients developed dermatitis following application of approximately equal amounts of MDBGN on both arms not distinguishing whether the allergen was applied as a 400 ppm solution once daily or a 100 ppm solution 4 times daily. Controls were negative.
Conclusions:  Applications with 400 ppm MDBGN once daily or 100 ppm MDBGN 4 times per day had, in a ROAT study, approximately equal capabilities of provoking allergic dermatitis in agreement with well‐known patch test data that dose per unit area is more important than concentration of allergen in the product. This may complicate risk assessment and regulation of cosmetic allergens. Further studies, however, are needed before more general conclusions can be made.     

Methyldibromoglutaronitrile allergy: relationship between patch test and repeated open application test thresholds

Background Methyldibromoglutaronitrile (MDBGN) is a preservative, which was approved for use in cosmetics in the mid‐1980s. The incidence of allergy to MDBGN rose during the 1990s, but is now decreasing due to regulatory intervention. Experimental studies with other allergens have shown a significant relationship between the patch test and the repeated open application test (ROAT) reactivity. Objectives To study the relationship between elicitation threshold doses at single occluded exposure and repeated open application, using MDBGN as the allergen. Methods Eighteen subjects allergic to MDBGN were tested with a dilution series of MDBGN in a patch test and a ROAT (duration up to 21 days). Seventeen people with no MDBGN allergy were included as a control group for the ROAT. Results The response frequency for the ROAT (in μg MDBGN cm^?2 per application) was significantly higher than the response frequency for the patch test, while the response frequency for the accumulated ROAT dose, at 1, 2 and 3 weeks was very similar to the patch test response frequency; indeed there was no statistical significant difference. Conclusions For elicitation of MDBGN allergy the response frequency for the patch test is lower than the response frequency (per application) for the ROAT, but approximately the same as the response frequency for the accumulated ROAT doses. This is important for risk assessment in general.     

Repeated open application test with methyldibromo glutaronitrile, a multicentre study within the EECDRG

Contact allergy to and allergic contact dermatitis from methyldibromo glutaronitrile (MDBGN) have frequently been reported. This study was initiated to help determine the optimal patch test preparation for MDBGN. In 51 patients with a doubtful or a positive patch test reaction to at least 1 of 4 test preparations with MDBGN in petrolatum at 1.0% w/w, 0.5%, 0.3% and 0.1%, a repeated open application test (ROAT) with moisturizers with and without MDBGN at 0.03% w/w was performed on the upper arms for 2 weeks. 18 of the 51 (35.3%) patients developed a positive ROAT. In all patients, there was a positive ROAT only to the moisturizer with MDBGN (P < 0.001). A statistically significant association was also found between the patch test reactivity (PTRL) and the outcome of the ROAT (P < 0.001). If only considering those with a PTRL above 0.3%, thus with negative or doubtful test reactions to 0.1% and 0.3%, there were still statistically significantly more patients with a positive ROAT to the moisturizer with MDBGN than to the moisturizer without MDBGN. The study demonstrates that patch testing with MDBGN at 0.3% and 0.1% will miss clinically relevant patch test reactions to MDBGN.     

A clinically relevant contact allergy to methyldibromo glutaronitrile at 1% (0.32 mg/cm) detected by a patch test

Recently, the preservative methyldibromo glutaronitrile (MDBGN) at 0.5% w/w in petrolatum was included in the European standard patch test series based on the studies on chemical stability and consideration of rates of contact allergy, doubtful and irritant reactions as well as information on clinical relevance represented by results of a repeated open application test (ROAT) and patch test concentrations required to diagnose allergic contact dermatitis from MDBGN in individual cases. In this report, a case with a clinically relevant contact allergy to MDBGN, which on the mandatory reading occasion on D3 only was traced by a patch test with MDBGN at 1.0% (0.32 mg/cm2), is presented. The patient suffered from a chronic hand dermatitis, and when the patient stopped using a liquid soap containing MDBGN, the hand dermatitis substantially improved. A ROAT performed in a blinded and controlled way with applications twice daily on the hands with 2 moisturizers with and without MDBGN resulted in a deterioration of the hand dermatitis on the hand to which the MDBGN-preserved moisturizer had been applied.     

Sodium tetrachloropalladate (Na2[PdCl4]) as an improved test salt for palladium allergy patch testing

Background:  In the last decades, palladium is widely used in dentistry. Allergic reactions to palladium are rarely diagnosed with patch testing, even when positive results would be expected. Palladium tends to cross-react with nickel, which should give rise to more positive reactions to palladium dichloride (standard test salt).
Objective:  The aim of the study was to test whether or not mono-nuclear sodium tetrachloropalladate (Na₂[PdCl₄]) in petrolatum is a better test salt for diagnosing palladium allergy. Positive reactions to the investigated test salt are compared not only with PdCl_2(aq.), but also to NiSO_4(aq.) and NiSO_4(pet.).
Patients/Methods:  Concentration series of Na₂[PdCl₄] were carried out. 164 consecutive patients were patch tested.
Results:  3% of Na₂[PdCl₄]_(pet.) was found to be the highest non-irritative concentration. The results show ( n  = 164) that Na₂[PdCl₄] covers all reactions to PdCl₂ (1.8%) and provokes more positive reactions (14%). From the 164 patients, 18.3% reacted positively to at least 1 of the nickel salts.
Conclusion:  The sensitivity of patch testing with Na₂[PdCl₄] is increased compared with the PdCl₂ salt. Therefore, it can be concluded that Na₂[PdCl₄] is to be a better test salt for diagnosing palladium allergy with patch testing.     

Is the variability of nickel patch test reactivity over time associated with fluctuations in the systemic T‐cell reactivity to nickel?

Background  Patch test reactivity to nickel varies over time. To what extent this variation is associated with fluctuations in the T-cell reactivity to nickel is not known.
Objectives  Our aim was to investigate the relationship between variation over time in the patch test and the systemic T-cell reactivity to nickel.
Methods  Patients ( n  =   15) with a history of contact allergy to nickel were subjected to three consecutive patch tests at 3-month intervals, utilizing NiSO₄ at 10 concentrations ranging from 0·0032% to 12·5%. Prior to each patch test, blood mononuclear cells were analysed for T-cell reactivity to nickel by interleukin (IL)-4 and IL-13 enzyme-linked immunospot assay.
Results  Eleven patients reacted positively in all three patch tests, two patients reacted in one or two tests and two remained negative. All 13 positive patients displayed variability over time, in terms of the lowest dose of nickel to which they responded. Also the cytokine response to nickel varied over time but the patients' mean cytokine response was positively correlated with their mean patch test reactivity ( r _s = 0·70, P  <   0·01 for IL-4; r _s = 0·78, P  <   0·001 for IL-13). However, although the changes over time in patch test reactivity and the cytokine responses to nickel displayed a similar pattern in many patients, there was no significant correlation between the individuals' variation over time in vivo and in vitro .
Conclusions  The overall magnitude of the T-cell reactivity to nickel and the patch test reactivity are closely associated but fluctuations in the systemic T-cell reactivity cannot be singled out as the major cause of longitudinal variability in nickel patch test reactivity.     

Methyldibromoglutaronitrile in rinse-off products causes allergic contact dermatitis: an experimental study

BACKGROUND: The frequency of sensitivity to the cosmetic preservative methyldibromoglutaronitrile (MDBGN) has increased significantly in Europe. Most cases of allergic contact dermatitis from MDBGN are caused by leave-on cosmetic products. The risk of developing allergic contact dermatitis from rinse-off products has been less studied. OBJECTIVES: To investigate the allergic response elicited in presensitized individuals from exposure to a rinse-off product preserved with the maximum permitted level of MDBGN. METHODS: Nineteen contact allergic individuals and nine controls participated in a double-blind, randomized repeated open application test (ROAT) using two coded liquid soaps with and without MDBGN. Areas of 50 cm2 on the lower arms were washed with the soaps twice a day for up to 28 days; two of the subjects continued for 34 days. The subjects were also patch tested with a dilution series of MDBGN to determine their patch test threshold values. RESULTS: Seven presensitized individuals (37%) developed allergic contact dermatitis from the soap containing MDBGN. The mean dose of MDBGN per application was 2.2 micro g cm-2 and the reactions appeared between days 6 and 34. All nine controls had negative ROATs. The difference in reactivity between test subjects and controls was significant (one-sided Fisher's exact test, P = 0.04). Patch test threshold values ranged from < 0.001% to 0.2% MDBGN in ethanol/water. CONCLUSIONS: This study shows that the exposure to a rinse-off product containing the maximum permitted level of MDBGN can easily elicit an allergic response in presensitized individuals. Along with reported cases of induction and elicitation caused by MDBGN in rinse-off products the study indicates that the permitted level of MDBGN in rinse-off products is too high. We recommend that this level should be re-evaluated.     

Quantitative patch and repeated open application testing in methyldibromo glutaronitrile-sensitive patients

Contact allergy to methyldibromo glutaronitrile (MDBGN), often combined with phenoxyethanol (PE) (e.g., Euxyl K 400), increased throughout the 1990s in Europe. Consequently, in 2003, the European Commission banned its use in leave-on products, where its use concentration was considered too high and the non-sensitizing use concentration as yet unknown. The 2 objectives of the study are (a) to find a maximum non-eliciting concentration in a leave-on product in MDBGN/PE-sensitized patients, which could possibly also be considered safe regarding induction and (b) to find the best patch test concentration for MDBGN. We, therefore, performed a use-related test (ROAT) in patients sensitized to MDBGN/PE (n = 39) with 3 concentrations of MDBGN/PE (50, 100 and 250 p.p.m. MDBGN, respectively). A subset of these patients (n = 24) was later patch-tested with various concentrations (0.1, 0.2, 0.3 and 0.5% MDBGN, respectively). 15 patients (38%, 95% confidence interval (CI) = 23-55%) had a negative and 24 (62%; 95% CI = 45-77%) a positive overall repeated open application test (ROAT) result. 13 reacted to the lowest (50 p.p.m.), 8 to the middle (100 p.p.m.) and 3 to the highest concentration (250 p.p.m.) only. In those 13 reacting to the lowest ROAT concentration, dermatitis developed within a few days (1-7). The strength of the initial and the confirmatory patch test result, respectively, and the outcome of the ROAT were positively associated. Of the 24 patients with a use and confirmatory patch test, 15 reacted to 0.1% MDBGN, 16 to 0.2%, 17 to 0.3% and 22 to 0.5%. With the patch test concentration of 0.5%, the number of ROAT-negative patients but patch-test-positive patients increases considerably, particularly due to + reactions. A maximum sensitivity of 94% (95% CI = 70-100%) is reached with a patch test concentration of 0.2%, and is not further improved by increasing the concentration. However, the specificity decreases dramatically from 88 (95% CI = 47-100%) with 0.2% to a mere 12.5% (95% CI = 0-53%) with 0.5%. It can be concluded (a) that for MDBGN 0.2% is very likely the best patch test concentration and (b) that 50 p.p.m. in a leave-on product can elicit contact dermatitis in sensitized persons. We were, therefore, unable to find a safe, still microbicidal, concentration for leave-on products. By contrast, with other contact allergens, dose-response use tests may be able to identify a non-eliciting concentration, which could give valuable clues to a non-inducing (i.e., safe) concentration in products.     

Nickel allergy: relationship between patch test and repeated open application test thresholds

BACKGROUND: The frequency of nickel allergy varies between different population groups. Exposure regulation has proven effective in decreasing the frequency. Experimental studies with other allergens have shown a significant relation between patch test reactivity and repeated open application test (ROAT) reactivity. OBJECTIVES: This study was aimed at determining the elicitation threshold in nickel-allergic individuals in a patch test and a ROAT, and comparing the threshold from these two test methods. METHODS: Twenty nickel-allergic persons were tested with a dilution series of 19 concentrations in a patch test and a dilution series of three concentrations in a ROAT, with duration of up to 21 days. Eighteen persons with no nickel allergy were included as control group for the ROAT. RESULTS: The predicted dose which will elicit a reaction in 10% of allergic individuals was calculated to be 0.78 microg nickel cm(-2) in the patch test. The threshold for the ROAT (in microg nickel cm(-2) per application) was significantly lower than the threshold for the patch test, while the dose-response for the accumulated ROAT dose at 1 week, 2 weeks and 3 weeks was very similar to the patch test dose-response; indeed, there was no statistically significant difference. CONCLUSIONS: For elicitation of nickel allergy the elicitation threshold for the patch test is higher than the elicitation threshold (per application) for the ROAT, but is approximately the same as the accumulated elicitation threshold for the ROAT. This may be important for risk assessment based on dose-response results from allergic patients.     

Attempts to mimic the repeated open application test in the guinea pig

The aim was to mimic the repeated open application test (ROAT) procedure, well established in humans, in an animal model. Guinea pigs were induced with cobalt chloride (CoCl₂). They were then challenged by repeated open application (4 sites/animal) of various concentrations of the allergen in 10% DMSO 1 × a day for 7 days, to study dose dependency, morphology of test reactions and time course. The reactivity at the test sites to repeated open application was dose-and time-dependent. There was good agreement between the results of the treatments with CoCl₂ and the post-treatment patch test results. Among 26 of the 29 animals, such agreement was found when 10% DMSO was used as vehicle. However, some reactivity was also observed in pretests at sites exposed to petrolatum. We suspect that this may be due to contamination and/or irritancy of the vehicle.     

Dose per unit area - a study of elicitation of nickel allergy

BACKGROUND: Experimental sensitization depends upon the amount of allergen per unit skin area and is largely independent of the area size. OBJECTIVES: This study aimed at testing if this also applies for elicitation of nickel allergy. PATIENTS/METHODS: 20 nickel allergic individuals were tested with a patch test and a repeated open application test (ROAT). Nickel was applied on small and large areas. The varying parameters were area, total dose and dose per unit area. RESULTS: In the patch test, at a low concentration [15 microg nickel (microg Ni)/cm(2)], there were significantly higher scores on the large area with the same dose per area as the small area. At higher concentrations of nickel, no significant differences were found. In the ROAT at low concentration (6.64 microg Ni/cm(2)), it was found that the latency period until a reaction appeared was significantly shorter on the large area compared to the small area. It was also found that the ROAT threshold (per application) was lower than the patch test threshold. CONCLUSION: For elicitation of nickel allergy, the size of the exposed area and therefore the total amount of applied nickel, influence the elicitation reaction at some concentrations, even though the same dose per unit area is applied.     

FS09.5Patch testing with allopurinol and oxypurinol in drug eruptions

The rapidly increasing frequency of contact allergy to methyldibromo glutaronitrile (MDBGN) is of concern. This study investigates the allergic response elicited in pre‐sensitised individuals from exposure to a leave‐on product preserved with 50 or 100 ppm MDBGN.
Material and methods:  Eighteen volunteers with contact allergy to MDBGN and 10 healthy controls were exposed to repeated open allication tests (ROAT) with two moisturisers with a high and a low lipid content, respectively, both containing MDBGN in a concentration of 50 ppm. The ROATs were performed on the left and the right side of the neck for 14 days, or until a positive reaction was seen. If a positive reaction did not develop within the first 14 days the application with analogous moisturisers containing 100 ppm MDBGN continued for further 14 days.
Results:  Eleven (61.1%) developed dermatitis on the test area, and 10 (55.5%) developed a positive reaction to 50 ppm moisturiser. Reactions to the low‐ moisturiser were the most frequent. the controls all had negative ROATs.
Conclusion:  A concentration of 50 ppm MDBGN in a leave‐on product was found to elicit an allergic reaction in more than half of sensitised individuals when applied on the neck.     

Quantitative patch and repeated open application testing in hydroxyisohexyl 3-cyclohexene carboxaldehyde sensitive-patients

Objective: To identify the concentration of the fragrance compound hydroxyisohexyl 3-cyclohexene carboxaldehyde (INCI) (HICC) that is sufficiently low not to cause an allergic reaction in patients with proven sensitization.
Methods: Repeated open application testing (ROAT) in 64 subjects with 2 preparations (perfume and cream) in different concentration (0.005–2.5%). Confirmatory patch testing with four preparations in two different concentrations (2.5% and 5%).
Results: The concentrations of HICC being tolerated by 90% of those sensitized to HICC are estimated as <88.2 ppm (cream) and <270 ppm (perfume) equivalent to 1.2 μg/cm² (perfume) and 4.9 μg/cm² (cream). Patch test preparations differed with regard to sensitivity (88.5–98.1%) and specificity (37.5–87.5%) against the ROAT result as external criterion. ROAT concentrations and the reaction strength in patch testing were inversely correlated (Kendall's tau-b: 0.69), both indicating the existence of different degrees of susceptibility.
Conclusion: To protect 90% (50%) of people sensitized, the use concentration should be in the range of 0.009–0.027% (0.18–0.34%), depending on the product type. Taking into account these results, excessive concentrations should be avoided, as this would continue to sensitize people. Close monitoring is indispensable to prove the efficacy of any recommendations aiming to prevent induction.     

Increased retest reactivity by both patch and use test with methyldibromoglutaronitrile in sensitized individuals

Hyperreactivity on re-exposure of previous allergic contact dermatitis skin areas has been previously demonstrated. This study aimed to investigate in methyldibromoglutaronitrile (MDBGN) allergic patients whether skin with previous allergic dermatitis from MDBGN showed an augmented response on re-exposure by both a patch test challenge and a use test with a liquid soap preserved with MDBGN. MDBGN dermatitis was elicited on the back and arms of sensitized individuals. One month later the previously eczematous areas were challenged with MDBGN. On the back, the test sites were patch-tested with a serial dilution of MDBGN and a use test was performed on the arms with an MDBGN-containing soap. A statistically significant increased response was seen on the areas with previous dermatitis on the back. Eight of the nine patients who developed dermatitis on the arms from the MDBGN-containing soap had an augmented response on areas with prior allergic contact dermatitis. Even though the allergic dermatitis appeared to be healed, an increased reactivity to allergen re-exposure was demonstrated both by patch test and use test challenge.     

Quantitative repeated open application testing with a rinse‐off product in methyldibromo glutaronitrile‐sensitive patients: results of the IVDK

Background: While the use of methyldibromo glutaronitrile (MDBGN) in leave‐on products is clearly associated with high sensitization or elicitation risk, such a clear‐cut relation could be questioned with regard to rinse‐off products. Objective: The objective of this study was to find a maximum non‐eliciting concentration for rinse‐off products in MDBGN patch test‐positive patients. Patients and methods: We performed a use‐related test [repeated open application test (ROAT)] in patients sensitized to MDBGN with a liquid soap containing three concentrations of MDBGN (50, 200, and 400 p.p.m. MDBGN, respectively). The soap at 50 p.p.m. was used twice daily for 4 weeks. If no reaction of the skin was observed, the product with the next higher concentration was used for another 4 weeks, etc. Results: In total, 32/37 evaluated cases [86.5%; lower exact one‐sided 95% confidence limit (CL): 73.7%] did not react to any of the preparations. The remaining reacted as follows: 1/37 reacted to 50 p.p.m., 3/37 to 200 p.p.m., and 1/37 to 400 p.p.m. The cumulative non‐response to 50 p.p.m. was 97.3% (lower CL: 87.8%). Conclusions: The majority of subjects sensitized to MDBGN‐tolerated rinse‐off products containing a maximum concentration of 400 p.p.m. A concentration in rinse‐off products in the range of 50 p.p.m. could be regarded as safe for most individuals already sensitized. These concentrations will presumably prevent induction (sensitization) also.     

Pretreatment of the test area with 1-day occlusion improves the response rate to NiSO4 5% pet. Patch tests in subjects with a positive history of nickel allergy

A group of 58 women, aged 18 to 51 years, with a clinical history of nickel allergy, who exhibited equivocal or negative reactions to nickel sulfate 5% pet, patch tests performed on the skin of the back, were recruited consecutively from the patch test clinic from September 1993 to June 19944. In order to improve the response rate to NiSO₄ 5% pet, patch tests, a testing procedure utilizing pretreatment of the test area by 1-day (24-h) occlusion was introduced. Patients underwent 2 patch tests on adjacent sites of the volar surface of both forearms. 3 of the patch tests were performed with 40 mg nickel sulfate 5% pet., whereas a control test was carried out by occluding with an empty chamber. 2 of the nickel sulfate test sites were pretreated with 1-day occlusion performed with an empty chamber. A visual grading system and echographic measurement were used to quantify the responses 30–40 min after patch test removal. Echographic evaluations were carried out using a 20 MHz B-scanner. Measurement of skin thickness and determination of the hypoechogenic dermal area, both considered to be parameters of inflammation, were used to evaluate the intensity of the allergic reaction. At the 3-day (72-h) evaluation. 19 subjects out of 58 clearly showed positive reactions to nickel sulfate 5% pet, at pre-occluded skin sites. Moreover, values of skin thickness and of 0–30 areas at positive pre-occluded nickel test areas were higher in respect to control test areas, confirming clinical evidence of increased response to NiSO₄, after occlusion.     

Decreasing trends in methyldibromo glutaronitrile contact allergy--following regulatory intervention

Background:  The preservative methyldibromo glutaronitrile (MDBGN) has been banned, first from stay-on, and later from rinse-off cosmetics, in the EU countries because of increasing rates of contact allergy.
Objectives:  To evaluate the frequency of contact allergy to MDBGN among patients patch tested by the Danish Contact Dermatitis Group just before and following regulatory decisions.
Patients/Methods:  The data set comprised 19 279 consecutive eczema patients patch tested from 2003–2007 with MDBGN 0.3% in petrolatum (pet.) or, in a minority of patients, with Euxyl K™ 400 1.5% in pet.
Results:  A significantly decreasing trend in the frequency of positive patch tests to MDBGN was found from 4.6% in 2003 to 2.6% in 2007 ( P  < 0.001). The decreasing trend was seen for both men and women. A significantly decreasing proportion of cases with a current relevance of contact allergy to MDBGN was also seen from 51.3% in 2003 to 29% in 2007 ( P  < 0.001).
Conclusions:  Regulatory interventions have already had a major effect on allergic disease due to MDBGN in Denmark. The same trends are likely to be seen in other EU countries.     

Ethosome formulation of contact allergens may enhance patch test reactions in patients*

Background: Ethosomes and liposomes are ultra‐small vesicles capable of encapsulating drugs and cosmetic ingredients for topical use, thereby potentially increasing bioavailability and clinical efficacy. So far, few reports have suggested that formulation of cosmetic ingredients in vesicular carrier systems may increase the allergenicity potential. Objectives: To investigate the effect of ethosome formulation of isoeugenol and methyldibromo glutaronitrile on the elicitation response under patch test conditions and by repeated open applications. Patients/Materials/Methods: A total of 27 volunteer patients with a previous positive patch test reaction to either isoeugenol or methyldibromo glutaronitrile were included in the study. In all patients, a serial dilution patch test was performed with the allergen in question formulated in ethosomes and in an ethanol/water solution. In addition, a repeated open application test (ROAT) was performed in a subset of 16 patients, and lag time until a positive response was recorded. Results: Both contact allergens encapsulated in ethosomes showed significantly enhanced patch test reactions as compared with the allergen preparation in ethanol/water without ethosomes. No significant difference in the median lag time was recorded between preparations in the ROAT. Conclusions: Encapsulating potential contact allergens in ethosomes may increase the challenge response as compared with the same concentrations in an ethanol/water base without ethosomes.     

Sensitizing potential in mice, guinea pig and man of the preservative Euxyl K 400 and its ingredient methyldibromo glutaronitrile

The allergenicity of the preservative Euxyl K 400 and its principal allergen methyldibromo glutaronitrile (MDBGN) (1,2-dibromo-2,4-dicyanobutane) was investigated using 3 animal models; in mice, the local lymph node assay (LLNA) and in guinea pigs, the guinea pig maximization test (GPMT) and the cumulative contact enhancement test (CCET) with a dose-response protocol included. Previous attempts to define the sensitization capacity of these chemicals have given conflicting results. For comparison, the frequency and causes of positive patch test reactions to Euxyl K 400 and MDBGN were studied in patients referred to an occupational dermatology clinic. This investigation showed that Euxyl K 400 and MDBGN can give rise to contact allergy in man and that the relevant cases found mainly had similar exposure as non-occupational cases. A contact allergenic potential could be detected for MDBGN in 2 animal models, i.e., the CCET and the LLNA, and also for Euxyl K 400 in the LLNA. However, statistical analysis of the results from the GPMT with MDBGN failed to detect the sensitizing potential of this particular allergen. The results indicate that to be able to detect the allergenic potential of Euxyl K 400 and MDBGN, a predictive test method with multiple topical applications at induction is required. It is therefore important that an investigator is aware of the possibility of using various predictive test models for investigation of potential contact allergens.