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.     

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.     

The dose–response relationship between the patch test and ROAT and the potential use for regulatory purposes

Background: Allergic contact dermatitis is common and can be prevented. The relationship between thresholds for patch tests and the repeated open application test (ROAT) is unclear. It would be desirable if patch test and ROAT data from already sensitized individuals could be used in prevention.
Objectives: The aim was to develop an equation that could predict the response to an allergen in a ROAT based on the dose–response curve derived by patch testing.
Materials/methods: Results from two human experimental elicitation studies with non-volatile allergens, nickel and the preservative methyldibromo glutaronitrile (MDBGN), were analysed by logistic dose–response statistics. The relation for volatile compounds was investigated using the results from experiments with the fragrance chemicals hydroxyisohexyl 3-cyclohexene carboxaldehyde and isoeugenol.
Results: For non-volatile compounds, the outcome of a ROAT can be estimated from the patch test by: ED_xx(ROAT) = 0.0296 ED_xx(patch test). For volatile compounds, the equation predicts that the response in the ROAT is more severe than the patch test response, but it overestimates the response.
Conclusions: This equation may be used for non-volatile compounds other than nickel and MDBGN, after further validation. The relationship between the patch test and the ROAT can be used for prevention, to set safe levels of allergen exposure based on patch test data.     

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.     

Experimental elicitation with hydroxyisohexyl-3-cyclohexene carboxaldehyde-containing deodorants

Hydroxyisohexyl-3-cyclohexene carboxaldehyde (HICC) known as Lyral is a frequent allergen. It is used in more than 50% of marketed deodorants. The aim of the present study was to determine elicitation thresholds for HICC under simulated conditions of deodorant use. 15 patients with previously diagnosed contact allergy to HICC were patch tested with 5 solutions of HICC-scented and HICC-unscented deodorants. Patients and 10 healthy controls performed a use test in the axillae using deodorants scented with HICC in increasing concentrations and unscented deodorants as control. The concentration of HICC was increased every second week (200, 600, and 1800 p.p.m.) until either a reaction developed or for 6 weeks. 14 patients completed the study, and all developed unilateral eczema from the HICC-containing deodorant, while controls were all negative (P= 0.004). In 9/14 patients, a positive use test developed during the first 2 weeks to the deodorant containing 200 p.p.m. HICC. Positive correlations were found between the day of positive use and patch test threshold concentration of the HICC solutions (r= 0.71, P= 0.01) as well as the patch test thresholds of the HICC-scented deodorants (r= 0.74, P= 0.007). In conclusion, HICC elicits allergic contact dermatitis in a high proportion of sensitized individuals at common usage concentrations in deodorants.     

Methylisothiazolinone contact allergy and dose-response relationships

Background. Methylisothiazolinone (MI) used alone is a new preservative causing a high prevalence of contact allergy. The eliciting threshold of MI is unknown. The combination of MI and phenoxyethanol enhances the antimicrobial efficacy of MI. Objectives. The eliciting doses of MI contact allergy in a patch test and a repeated open application test (ROAT) were investigated. In the patch test, it was determined whether phenoxyethanol influenced the reactivity to MI. Methods. Eleven MI‐allergic individuals were patch tested with two dilution series of 12 doses of MI and the same 12 doses with phenoxyethanol. The ROAT mimicked the use of a cream preserved with 100, 50 and 5 ppm MI (corresponding to 0.21, 0.105 and 0.0105 µg MI/cm²). Results. Phenoxyethanol had no influence on the reactions to MI. The lowest eliciting dose in the patch test was 1.47 µg MI/cm². In the ROAT, 7 patients (64%) reacted to 0.21 and 0.105 µg MI/cm² and 2 patients (18%) reacted to 0.0105 µg MI/cm², corresponding to a cream preserved with 5 ppm MI. Conclusions. A maximum of 100 ppm MI is permitted in cosmetic products. Eighteen per cent of MI‐allergic patients reacted to a concentration 20 times lower in a ROAT. The amounts used in cosmetics should be reduced, and the development of MI contact allergy should be monitored closely.     

An evaluation of dose/unit area and time as key factors influencing the elicitation capacity of methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) in MCI/MI-allergic patients

Methylchloroisothiazolinone and methylisothiazolinone (MCI/MI) contact allergy affects 1-3% of patch-tested patients in European centres. The aim of the present study was to evaluate the importance of the factors--time and concentration (dose/per unit area)--in the elicitation capacity by means of a repeated open application test (ROAT) experimental design. The study was designed as a double-blind, placebo-controlled, dose-response ROAT preceded by a diagnostic patch testing. 25 subjects with confirmed MCI/MI allergy and 10 healthy, non-MCI/MI allergic control subjects were exposed to 0.025 microg/cm2 (2 p.p.m.) of MCI/MI/unit area of the skin for 4 weeks. After a wash-out period of at least 4 weeks, the subjects were exposed to 0.094 microg/cm2 (7.5 p.p.m.) of MCI/MI/unit area of the skin for 4 weeks. The study showed the importance of both time and exposure in the elicitation process. It demonstrated that the elicitation threshold for MCI/MI is expected to be in the proximity of 0.025 microg/cm2 although it was not possible to establish a definitive elicitation threshold for MCI/MI in this study.     

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.     

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.     

Investigation of the threshold for allergic reactivity to chromium

Allergy to chromium is relatively common, often in association with exposure to cement or in leather manufacture. However, in certain locations, there appears to be a relatively large cohort of chromium-sensitive individuals whose allergy cannot be explained by these common sources. In particular, this group include Israeli housewives with persistent hand eczema and concomitant patch test positivity to chromium. The causation of their allergy has been linked with relatively high levels of chromium contamination in household products. To provide further information in respect of the definition of safe levels for such products, we examined 17 chromium-allergic individuals to determine their threshold for reaction under closed patch test and repeated open application test (ROAT) conditions. The data derived indicated that, on normal skin, the patch test threshold was 10 ppm chromium; in the presence of an irritant (sodium lauryl sulfate) the threshold was closer to 1 ppm, 2/17 subjects giving 1+ reactions at this concentration. In the more realistic exposure conditions of the ROAT, 8/14 individuals failed to react to 50 ppm, whilst 3/15 reacted to 5 ppm. Interestingly, there was very poor correlation between patch test sensitivity and ROAT sensitivity. To ensure the large majority of chromium-allergic individuals do not suffer elicitation of their allergy, as well as to limit the development of new chromium-sensitive subjects, it is recommended that household products adhere to a previously published standard of a maximum limit of 5 ppm, with an ultimate target of 1 ppm contamination by chromium.     

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.     

FS04.1Formaldehyde allergy – clinically relevant threshold reactions

The objective of the study was to establish eliciting threshold concentrations of diazolidinyl urea (Germall II)– derived formaldehyde in formaldehyde and/or in diazolidinyl urea – sensitive patients, using a leave‐on face cream formulation in a repeated open application test (ROAT) applied to different anatomical regions.
150 patients with known formaldehyde allergy were reviewed for inclusion in the study. 108 patients were contacted and in 65 patients the formaldehyde sensitisation was reconfirmed by a patch test. Four groups of 10 formaldehyde allergic subjects were exposed to 0.05%, 0.15%, 0.3% and 0.6% diazolidinyl urea, corresponding to approximately 50, 100, 200 and 400 ppm free formaldehyde, respectively.
Additional 10 individuals allergic to the formaldehyde donor – diazolidinyl urea itself – were exposed to 0.15% diazolidinylurea, corresponding to approximately 100 ppm free formaldehyde and 10 healthy non‐allergic individuals were exposed to 0.6% of diazolidinylurea (approximately 400 ppm free formaldehyde).
A ROAT was performed in a scheduled sequence: upper arm, neck and face.
Contact allergy reactions were elicited in 39 out of 58 formaldehyde‐sensitive and in 5 out of 7 diazolidinyl urea‐sensitive individuals.
Elicitation responses were dose‐ and anatomical region – dependent.
No reactions were observed at the lowest dose, suggesting that an elicitation threshold was attained in the study.     

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.     

Use tests: ROAT (repeated open application test)/PUT (provocative use test): an overview

As one step in defining the clinical relevance of exposure to an allergen identified with patch testing, use tests (provocative use test (PUT), and repeated open application test (ROAT)) have been used. In 1/2 of the cases of seemingly reliable patch tests, use tests are negative, suggesting that the patient's biologic threshold of response had not been reached with open application dosing. Dramatic differences exist in regional skin reactivity and percutaneous penetration. Negative results of use tests on normal skin may become positive on diseased skin. To refine this assay further, more controlled observations and analysis of reaction differences between normal and damaged skin, and among regional anatomic sites might be performed. In addition, we require a standardized measurement for the results. Use testing has significant potential in refinement of the evidence-based diagnosis of clinical relevance. However, for general validation, we should fill the deficiencies described above.     

Threshold for occluded formaldehyde patch test in formaldehyde-sensitive patients

Our purpose was to investigate the eliciting threshold concentration of formaldehyde in formaldehyde-sensitive individuals in the occluded and non-occluded patch teat and to evaluate the relationship in repeated open application test (ROAT) with a product containing a formaldehyde releaser. 20 formaldehyde-sensitive patients and a control group of 20 healthy volunteer were included in the study. Occluded and non-occluded patch tests with formaldehyde solutions form 25 to 10,000 ppm. and ROAT for I week with a leave-on cosmetic product containing on average 300 ppm formaldehyde. Were carried out simultaneously on each subject. In the occluded patch test. 1/2 of the 20 patients only reacted to 10,000 ppm formaldehyde. 9 reacted to 5,000 ppm. 3 reacted to 1.000 ppm. 2 reacted to 500 ppm and I reacted to 25 ppm. No definite positive reactions were observed in the non-occluded patch test or in the ROAT No positive reactions were observed in the control group to any of the test procedures. We concluded that the threshold concentration for occluded patch test to formaldehyde in formaldehyde-sensitive patients was 250 ppm. The threshold in occluded patch test corresponded to the degree of sensitivity Definite positive reactions in the ROAT were not seen, either indicating that they are unlikely to happen with the type of product used or that the exposure time was too short.     

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.     

FS04.6Dose/unit area and time – key factors influencing the elicitation capacity of MCI/MI

The objective of the study was to investigate, using the Repeated Open Application Test (ROAT), two key parameters of exposure – allergen concentration (dose/unit area) and time in terms of the elicitation capacity of methylchloroisothiazolinone and methylisothiazolinone (MCI/MI) in MCI/MI‐sensitised individuals and to explore the inter‐relationship between these two key factors. The study was designed as a double‐blind, placebo‐controlled, dose‐response ROAT preceded by a Diagnostic Patch Test (DPT). 79 patients with a known MCI/M allergy were contacted, 29 were diagnostically patch tested and 25 had their allergy confirmed. 25 MCI/M‐allergic subjects and 10 healthy non‐allergic control subjects were challenged with 2 ppm of MCI/MI/unit area of skin for 4 weeks. After a wash out period of at least 4 weeks the subjects were challenged with 7.5 ppm of MCI/MI/unit area of skin for 4 weeks. A ROAT with 2 drops of solution twice a day was conducted on the volar aspect of the left and right forearms on a 3 × 3 cm area resulting in dose/unit area of MCI/MI of 0.025 mg/cm² and 0.095 mg/cm² for 2 ppm and 7,5 ppm MCI/MI respectively. The elicitation capacity of MCI/MI in MCI/MI sensitive patients is dependent on the exposure dose/unit area and time The results of this study will be a useful addition to the risk assessment information available for MCI/MI. The risk assessment for the use of MCI/MI in rinse off consumer products is unaffected by the results of this study.     

Contact allergy to calcipotriol does exist. Report of an unequivocal case and review of the literature

A 64-year-old woman developed an itchy papulovesicular dermatitis at the periphery of psoriatic plaques on the lower legs after the daily application of calcipotriol ointment (Psorcutan Salbe) for 2 weeks. She had used the same ointment for 4 weeks 6 months before. Patch testing revealed strongly positive reactions to the marketed product and to the active ingredient calcipotriol in a concentration series (2.0, 10.0 and 50.0 microg/ml in isopropyl alcohol). A repeated open application test (ROAT) on the forearms showed a vesicular dermatitis after 4 days on the side that received the calcipotriol ointment, whereas the control with the placebo ointment remained completely negative. Histologic examination of the + + patch test reaction was in line with the picture of contact allergy. Retesting after 6 months confirmed the hypersensitivity, with a positive reaction even at 0.4 microg/ml. For comparison, the ROAT with calcipotriol ointment was performed for 2 weeks on both forearms of 15 volunteers never exposed to calcipotriol before. Only 2 subjects developed a slight reaction on days 5 and 11, respectively. Based on this case and on previous reports in the literature, calcipotriol must now be regarded as both a contact allergen and an irritant. For patch testing, a concentration of 2 microg/ml in isopropyl alcohol is the most suitable. If the reaction is only weakly positive and not reproducible after some time, it might be of the irritant type. In unclear cases, a ROAT should be performed. A severe papulovesicular dermatitis within 1 week will confirm the presence of contact allergy.     

Atopy patch test reaction to airborne allergens in the diagnosis of atopic dermatitis

The aim of the study was to evaluate the possible use of atopy patch test in the diagnosis of atopic dermatitis and to characterize an optimal standardized system for atopy patch test in terms of allergen concentrations and time of allergen exposure. The study included 36 patients with atopic dermatitis and IgE-mediated airborne allergy. Patients presented positive results of skin prick tests and serum antigen specific IgE against house dust mite allergens and/or selected grass pollen allergens. Control groups consisted either of patients with allergic rhinitis (control group 1) or healthy volunteers with no signs or symptoms of atopy (control group 2). Allergologic diagnostic workup consisted of skin prick test, serum antigen specific IgE and total IgE evaluation, atopy patch test with selected airborne allergens of different concentrations (0.1xSPT, 1xSPT and 10xSPT), time of allergen exposure (8, 24 and 48 h), and readings of the results (8, 24, 48 and 72 h). Positive results of atopy patch test with airborne allergens were obtained in 47.2% of atopic dermatitis patients and none of control subjects. Contact reaction itself and the intensity of reaction were demonstrated to correlate with allergen concentration and time of allergen exposure on atopy patch test. The dose and time response analysis showed the optimal concentration of allergens for atopy patch test to be 10xSPT, 500000 SBE/ml, and optimal evaluation time 24 and 48 h of allergen application. There was no correlation between atopy patch test results and mean serum concentrations of total or antigen specific IgE. Atopy patch test results did not correlate with localization of skin lesions, severity and extensiveness of skin inflammation. A significantly higher contact reactivity to airborne allergens was recorded in the group of atopic dermatitis patients with polyvalent allergy in comparison with atopic dermatitis patients allergic to only one aeroallergen. It is concluded that atopy patch test is the only provocation test currently available with clinical relevance for contact IgE-mediated sensitization in atopic dermatitis patients. Using petrolatum as a vehicle, allergen concentration of 500000 SBE/ml and evaluation time of 24 and 48 h of allergen application may lead to improved atopy patch test results.     

The repeated open application test (ROAT)

Repeated open application tests (ROATs) were performed with common ingredients of vehicles in 86 patients with contact dermatitis. The substances were applied twice daily for 7 days to the flexor aspect of the forearm near the cubital fossa, unless dermatitis appeared earlier. Of the patients with a questionable (?+) patch test result, 44% were positive in ROATs. The corresponding figure was 80% in the patients with B positive (+ or ++) response in the patch lest, when the results of ROAT with propylene glycol were excluded. Only 5 of 14 patients reacting lo 30% or to 10% propylene glycol but not in 15 in water in patch testing, showed a positive result to a cream containing 5% propylene glycol in ROAT. All 5 patients with a positive patch test reaction to 1% propylene glycol reacted to 5% propylene glycol in ROAT. The results suggest that ROATs should be performed more often, especially in patients in whom little known or new allergens are suspected as being the cause of allergic contact dermatitis.