Contact dermatitis with negative patch tests: the additive effect of allergens in combination

We deduced on theoretical grounds that conventional patch testing would be inadequate for the detection of sensitivity to multiple allergens. Fourteen patients with positive patch tests to two unrelated allergens were studied and the response to those two allergens was measured when tested singly or in combination, using 10 different pair combinations from 15 common allergens. With serial dilutions in chloroform (14 patients) and paraffin (four patients), the response was related to the log-dose of the allergen, and change in skin-fold thickness corresponded well with clinical grading. Single allergens diluted below the threshold for a patch-test response gave a response when given in combination, the threshold for a response to one allergen being lowered by the presence of another. On the linear part of the dose-response curves the response to the mixture of allergens was additive, the combined response being the sum of the individual components. Approaching the plateau region the response to the combination was greater than to the individual allergens but less than the sum of the single responses. The same results were obtained with allergens in paraffin. We conclude that conventional single allergen patch testing by itself is inadequate for the diagnosis of contact dermatitis.     

Patch test reaction on Ethiopian subjects with eczema

Background  Allergic contact dermatitis is a common condition with an incidence of 1–10% in the general population. An increasing number of allergens in the environment are responsible for the condition. These allergens can be identified using patch testing. Many countries have a standard series of common allergens used for patch testing. There is no standard series of allergens in Ethiopia, and our objective was to obtain baseline data for common allergens for future standardization.
Methods  One hundred and eighty-one subjects with eczema were patch tested using 17 selected allergens from Chemotechnique Diagnostics AB employing a standard procedure.
Results  Positive patch test reactions were detected in more than 60% of subjects, the most common allergen being nickel, followed by fragrance mix and butylphenolformaldehyde. A higher incidence of positive reactions was seen in females.
Conclusions  A high incidence of positive patch test reactions was identified in the study population, and the introduction of patch testing in Ethiopia is essential for the management of allergic contact dermatitis.     

P34Reproducibility of the positive patch test reactions with the TRUE Test

The patch test results of patients tested at least twice at our clinic during a period of 11 years were analyzed with regard to reproducibility of the positive patch test reactions found in the first patch testing session.
A retrospective analysis of 257 patients who have been tested with the TRUE Test at least twice between 1991 and 2002 and had a minimum of one positive reaction in the first testing session was done. Test reactions were read routinely after 3 and 5–7 days.
In the first testing session a total of 299 positive reactions were found. Of these allergens, 151 (51%) stayed positive in the second test, 31 (10%) produced a doubtful reaction, 67 (22%) a negative response, and 50 (17%) were not retested because of strong positive reactions in the first test. Of the individual allergens, positive reactions from thiuram‐mix, kathon CG and colophony were the most reproducible.
If it is assumed that allergens which were not retested because of strong positive reactions would have shown positive reactions in a retest, a total of 68% of positive reactions were reproduced. A multitude of factors, such as: avoidance of relevant allergens between tests, diminished sensitivity, retesting within a period of more or less active dermatitis, different observers, methodological error, and prior false‐positive responses, influence the reproducibility of patch tests. The results will be put in perspective.     

Reproducibility of patch test results: a concurrent right-versus-left study using TRUE Test

Wide variations in the reproducibility rate of positive patch test responses have been reported. We hypothesized that a major source of non-reproducibility resides in the methodological pitfalls of routine patch testing. Simultaneous duplicate patch testing on opposite sides of the upper back was performed on 500 consecutive patients, using the TRUE Test system consisting of 2 panels, each one containing 12 standard allergens. A rigorous methodological design was applied and relevance was assessed for all discordant patch test reactions. A total of 435 positive patch test reactions were observed either on one or both sides in 289 patients (58.8%). Of these, 22 (5%) were discordant, i.e. interpreted as positive allergic on one side whilst negative or doubtful on the opposite side. The allergens responsible for discordant reactions were nickel sulfate (4 patients), cobalt chloride (3), lanolin alcohol (3), fragrance mix (2), carba mix (2), thiuram mix (2), colophonium (1), potassium dichromate (1), p-phenylenediamine (1), formaldehyde (1), balsam of Peru (Myroxylon pereirae resin) (1) and thimerosal (1). Of the 19 (4%) patients with discordant patch test reactions, the allergen was deemed to be of definite present or past relevance in 9 patients (1.8% of the total and 3.1% of all patients with positive patch test reactions) and of possible relevance in a further 2 patients. These data suggest that patch testing is a reasonably reproducible procedure as long as methodological error is minimized.     

Results of patch testing with a special series of rubber allergens

The purpose of this study was to examine the results of patch testing with the rubber components on a standard screening tray and compare them with the results of testing with a special series of 27 rubber components (rubber tray). 1670 patients were patch tested with the screening tray and 317 of these were also tested with the rubber tray 16% of those tested with the rubber tray had a positive response to at least 1 of the rubber allergens on the screening tray and 22% had a positive response to at least 1 of the allergens on the rubber tray. The most common positive response to the rubber tray allergens was to tetramethylthiuram monosulfide. There were no responses to 3 of the components on the rubber tray and there was only 1 positive response to a further 4 components. The diagnostic test characteristics of the rubber components on the screening tray were examined using the rubber tray as the gold standard. The sensitivity of the screening tray was 94%, specificity 51%, positive predictive value 87%, and negative predictive value 71% Of the 317 tested. 11%, were found to have a positive to a substance on the rubber tray that was not evident from the results of the screening tray patch testing technique: allergic contact dermatitis; rubber allergens: false-negative reactions: fake-positive reactions.     

Positive photocontact responses are not elicited to sunscreen ingredients exposed to UVA prior to application onto the skin

Photocontact allergic reactions to sunscreen chemicals are investigated by photopatch testing. It has generally been assumed that for photocontact allergy to be shown, the putative pro-allergen must be in the skin at the time of ultraviolet A (UVA) exposure. However, this assumption has not, to our knowledge, been tested. The objective of this study was to determine whether positive photocontact responses can still be elicited when sunscreen chemicals are exposed to UVA prior to application onto the skin. 3 patients known to have positive photocontact reactions to a total of 6 sunscreen chemicals were studied. For conventional photopatch testing, patch test strips were applied onto the back and removed 1 D later, and the area was irradiated with UVA (5 J/cm(2)). For pre-irradiated testing, patches were exposed to the same dose of UVA immediately before application onto the back and then removed 1 D later. Skin responses were visually assessed by a blinded investigator 1 and 2 D after patch test removal. The same photocontact responses of the same magnitude, as previously documented for each patient, were seen at each of the conventional UVA-exposed patch test sites. However, in no patient was a positive response elicited at any of the sites where pre-irradiated patches had been applied. This study shows that positive photocontact responses to sunscreen chemicals do not occur when the putative pro-allergen is irradiated prior to application onto the skin. This suggests that for a photoallergic reaction to occur, the sunscreen chemical needs to be within the skin when activated by UVA.     

Patch testing with a standard allergen ("screening") tray: rewards and risks

The TRUE Test panels, which are the only patch testing devices approved by the Food and Drug Administration in the US, consist of 24 patches, one of which is a negative control. The remaining 23 patches contain 42 unique allergens and four complex mixtures. Although these panels contain approximately 1.4% of the > 3700 known allergens, they perform robustly in detecting allergic contact dermatitis (ACD). Twenty-eight percent of patients are fully evaluated by application of TRUE Test((R)). The present paper reviews the appropriate use of the TRUE Test panels. The need to determine relevance of any positive reaction is stressed. The common causes of false-positive and false-negative reactions are outlined. Those product types where the TRUE Test panels detect the majority of relevant allergic reactions are reviewed, as are the other sources of exposure to the allergens on these panels. The impact of ACD on quality of life is significant. Only by patch testing can the diagnosis be made.     

Associated positive patch test reactions to standard contact allergens.

BACKGROUND: Patch testing with a standard allergen series often yields positive reactions to more than 1 allergen in a patient. OBJECTIVE: To identify all significantly associated pairs of positive reactions and to assess their relation to the strength of the reactions and to the irritative potential of the allergens. METHODS: Based on the filed data of 57,822 patients, associations between positive reactions to 2 different allergens were quantified with odds ratios. Statistical methods included Fisher's exact test, the Bonferroni adjustment to account for the effect of multiple testing, and the Spearman rank correlation. RESULTS: Out of the 32,779 patients with complete readings of 24 standard allergens, 7,501 had shown more than 1 positive reaction. Statistically significant associations were detected for 166 out of the 276 possible different combinations of 2 distinct positive reactions, including combinations that had not been identified before. Patients with a strong reaction or a positive reaction to an allergen with a high irritative potential tended to have additional positive reactions to further allergens more often than others, but the number of significant associations was not dependent on these parameters. CONCLUSION: There are more significant associations that have to be taken into account for patch testing than has been known so far. Although irritation can favor a higher number of positive reactions, significant associations of positive reactions to distinct allergens are probably caused by other mechanisms that require further analyses.     

Patch testing with fine fragrances: comparison with fragrance mix, balsam of Peru and a fragrance series

High frequencies of contact allergy to fragrance ingredients have been reported in recent years. Only approximately 70-80% are detected by fragrance allergens in the standard patch test series. This investigation compares the patch test reactions to fine fragrances with reactions to fragrance mix (FM), balsam of Peru (BP) (Myroxylon pereirae resin) and a fragrance series. 641 consecutive patients with eczema were patch tested with the European standard series and with selected fine fragrances. Those who were positive to 1 of the fine fragrances or the FM or BP were also tested with the fragrance series. 95 (14.8%) patients were found to have a positive patch test reaction to FM or BP; 41 (6.4%) had positive results to fragrance no. 1 and 29 (4.5%) to no. 2. 9 (9.5% of the 95 positive patients) had a positive reaction to fine fragrances and a negative reaction to all other fragrance allergens in the standard series. These findings indicate that testing with fine fragrances can add to our evaluation of fragrance-sensitive patients.     

Positive patch tests with a dermatophagoides mix relate to an increased responsiveness to standard patch test allergens

The diagnostic meaningfulness of patch tests with house dust mite allergens is still questionable. Our own impression has been that positive results with a dermatophagoides mix may occur preferentially in patients with a generally enhanced responsiveness to contact allergens. To check this, all of our patients allocated to patch testing with the standard series were additionally patch tested with a dermatophagoides mix by the same technique that was used for standard contact allergens. Out of 571 patients tested, 188 showed delayed responses to this mix that were indistinguishable from typical allergic patch test reactions but of no apparent clinical relevance. No relationship was found between positive dermatophagoides patch tests and an atopic disposition of the patients or characteristics of their eczema. However, 64.4% of the patients with a positive dermatophagoides patch test showed a response to at least 1 contact allergen of the standard series, compared to only 56.4% of the patients without a positive dermatophagoides reaction (p < 0.05). The reactivity to the mite mix was not related to the responsiveness towards any particular contact allergens. We suppose that some unidentified factors may contribute to positive reactions to the dermatophagoides mix that may also favour an enhanced general responsiveness to contact allergens.     

Clinically relevant patch test reactions in children--a United States based study

Allergic contact dermatitis in the pediatric population is more common than previously recognized, with recent prevalence estimates of positive patch test reactions in the range of 14-70% of children patch tested. The aim of this study was to confirm the prevalence of clinically relevant allergic contact dermatitis in children at two referral centers and determine the most common contact allergens. We performed a retrospective case series analysis of 65 symptomatic children (35 girls and 30 boys) aged 1-18 years old who were patch tested over a 5-year period for recalcitrant dermatitis. Positive patch test reactions were noted in 54 of the 65 children (prevalence rate of 83%) to 80 different allergens. Fifty children (77%) had positive reactions which were determined to be of "definite" or "probable" current clinical relevance. We conclude that the diagnosis of allergic contact dermatitis to specific relevant allergens is common in children referred for patch testing and that contact allergy should be considered in all children with recalcitrant dermatitis. With this article, we review the literature and present a US based study regarding the clinical relevance of positive patch test reactions in children.     

European multicenter study of the TRUE Test™

A new, standardized, ready-to-apply patch test, the TRUE Test, has been evaluated on 698 consecutive patients with suspected contact dermatitis. The patients were tested with 12 different allergens. Simultaneously, the same 12 allergens in pet. (Trolab) were applied symmetrically to the opposite side of the upper back using the conventional Finn Chamber technique. There were positive test reactions to all 12 allergens tested in the patient group. The concordance of positive reactions between the TRUE Test and the Finn Chamber test was 67%; 13% of all positive reactions were recorded only for the TRUE Test and 20% only for the Finn Chamber method. The frequency of questionable and irritant reactions was of the same low order of magnitude for both test methods; such reactions were recorded in around 2% of all test patches.     

Textile dermatitis in Israel: a retrospective study.

BACKGROUND:The diagnosis of contact dermatitis caused by clothing may be difficult because of its clinical polymorphism. Data in the literature suggest that textile dermatitis is more common than previously thought. OBJECTIVE: Our purpose was to study our patients suspected of having textile contact dermatitis from 1991 to 1997. METHODS: The records of the patients with positive reactions to allergens from the Textile Colors and Finish series in 3 contact dermatitis clinics were reviewed. All the patients were clinically evaluated and patch tested with the European Standard series and the Textile Colors and Finish series (Chemotechnique Diagnostics, Malm?, Sweden). RESULTS: Twenty-two of the 55 patients (40%) had positive patch tests to the textile dye allergens. Four of them had occupationally related textile dermatitis. The most frequent allergens were Disperse Blue 124, Disperse Blue 85, Disperse Red 17, and Disperse Blue 106. Erythematosquamous lesions were the most common forms of textile dermatitis (56%), followed by pustular lesion (16%) and hyperpigmented patches (8%). CONCLUSIONS: The relatively high percentage of positive results (40%) was attributable to the selected cohort of patients. In our series, positive reactions to the allergens Disperse Blue 124, 85, and 106 were common findings. Clinically, pustular allergic contact dermatitis, triggered by textile dyes was observed along with the more frequent erythematosquamous clinical form.     

Measurement of a possible patch‐testing outcome indicator

Background: Clinical performance measurements often employ outcome indicators to express the extent to which health services achieve a given clinical result. Objective: The objective of our study was to develop an outcome indicator of patch testing. We identified and measured as a possible indicator the ratio of patients with allergic and/or photo‐allergic contact dermatitis clinically cured/improved as a result of identification of relevant allergens. Patients/Methods: Patients with positive reactions considered relevant to their current dermatitis were interviewed by telephone 2 months after patch/photo‐patch testing in order to assess their clinical outcome in relation to the recommended elimination of supposedly relevant allergens. Results: Over a 4‐year period positive reactions were seen in 1397 out of 2857 tested patients. Relevance was considered current in 578 subjects, and 506 of them were interviewed. Remission/significant improvement following allergen(s) contact avoidance was reported by 431 patients, the outcome indicator (431/506) thus scoring 85.2%. Among the 75 patients who reported no improvement, 41 had not avoided contact with the offending substance(s), 17 had other persistent concomitant skin conditions, and 17 were unchanged despite elimination of the alleged relevant allergens. Conclusions: The ratio of relevantly patch‐test‐positive patients resolved/improved after allergen avoidance is a useful patch‐testing outcome indicator.     

North American Contact Dermatitis Group patch test results for the detection of delayed-type hypersensitivity to topical allergens

Background: Allergic contact dermatitis is a significant cause of cutaneous disease affecting many individuals. Patch testing, when used properly, often provides support for the diagnosis of allergic contact dermatitis. Objective: This article reports patch testing results from July 1, 1994, to June 30, 1996, by the North American Contact Dermatitis Group (NACDG). Methods: Patients evaluated in our patch test clinics were tested with the same screening series of allergens by the use of a standardized patch testing technique. The data from these patients were recorded on a standard computer entry form and analyzed. Results: Forty-nine allergens were tested on 3120 patients. Budesonide was added to the series in July 1995 and tested on 1678 patients. Of these patients, 66.5% had positive allergic patch test reactions, and 57% had at least one allergic reaction that was felt to be clinically relevant to the present or past dermatitis. The 20 screening allergens commercially available to United States dermatologists in the Allergen Patch Test Kit, accounted for only 54.1% of the patients with positive allergic reactions. The additional 30 allergens on the NACDG screening series accounted for 47% of patients with positive allergic reactions. Had the Allergen Patch Test Kit alone been used, 12.4% of all patients tested may have had their disease misclassified as a nonallergic disorder, and an additional 34.4% of all tested patients would not have had their allergies fully defined. Among those patients with positive responses to the supplemental allergens, 81% of the responses were of present or past relevance. The 12 most frequent contact allergens were nickel sulfate, fragrance mix, thimerosal, quaternium-15, neomycin sulfate, formaldehyde, bacitracin, thiuram mix, balsam of Peru, cobalt chloride, para-phenylenediamine, and carba mix. The present relevance varied with the specific allergen from 10.7% (thimerosal) to 85.7% (quaternium-15). Among newer allergens, methyldibromoglutaronitrile/phenoxyethanol (cosmetic preservative) caused positive allergic reactions in 2% of the patients; tixocortol-21-pivalate and budesonide (corticosteroids), in 2.0% and 1.1% of the patients, respectively; and ethylene urea/melamine formaldehyde mix (textile resin), in 5% of the patients. Conclusion: The usefulness of patch testing is enhanced with the number of allergens tested, because allergens not found on the commercially available screening series in the United States frequently give relevant allergic reactions. (J Am Acad Dermatol 1998;38:911-8.)     

Simultaneous sodium lauryl sulphate testing improves the diagnostic validity of allergic patch tests. Results from a prospective multicentre study of the German Contact Dermatitis Research Group (Deutsche Kontaktallergie-Gruppe, DKG)

Background There is evidence that a higher skin susceptibility may induce nonspecific erythematous or weak positive reactions to contact allergens in patch testing. Objectives To evaluate whether simultaneous application of sodium lauryl sulphate (SLS) along with diagnostic patch tests with contact allergens can provide information regarding skin irritability which may help to discriminate allergic from nonspecific irritant reactions to contact allergens. Methods Between July 2001 and June 2003, this prospective study collected patch test data of 5971 patients from 19 centres in Germany and Austria in the Information Network of Departments of Dermatology (IVDK). In addition to contact allergens (standard series and eight known ‘problematic’ allergens with a low reaction index and a high positivity ratio: 1,3‐diphenylguanidine, amerchol L‐101, benzalkonium chloride, benzoyl peroxide, cocamidopropyl betaine, octyl gallate, phenyl mercuric acetate and propylene glycol), patches with SLS 0·5% and 0·25% aq. were applied. Reactions to the allergens and to SLS were analysed at the IVDK data centre. The association between an erythematous or positive reaction to a certain allergen and an irritant reaction to SLS was assessed with logistic regression analysis, at the same time controlling for the influence of age and sex. Results Of the 29 allergens of the standard series, 23 and 21 gave a higher percentage of nonspecific erythematous reactions in patients with an irritant reaction to 0·25% and 0·5% SLS, respectively, in comparison with SLS‐negative patients. All eight ‘problematic’ allergens gave an increased percentage of nonspecific erythematous reactions. Similarly, 22 and 21 allergens of the standard series gave a higher percentage of positive allergic reactions in patients with an irritant reaction to 0·25% and 0·5% SLS, respectively, and seven of the eight ‘problematic’ allergens gave a higher percentage of positive allergic rections (exception: octyl gallate). For most allergens, the markers of skin reaction (reaction index and positivity ratio) were worse in SLS‐positive patients. Differences were more pronounced when testing with SLS 0·25% than with SLS 0·5%. Conclusions Because there is a convincing association between skin irritability (evaluated by SLS test) and the degree of skin reaction to contact allergens, the SLS test may help in deciding whether a doubtful erythematous or weakly ‘positive’ skin reaction should be interpreted as allergic or irritant.     

Patch testing is a useful investigation in children with eczema

Background. Allergic contact dermatitis in children is less recognized than in adults. However, recently, allergic contact dermatitis has started to attract more interest as a cause of or contributor to eczema in children, and patch testing has been gaining in recognition as a useful diagnostic tool in this group. Objectives. The aim of this analysis was to investigate the results of patch testing of selected children with eczema of various types (mostly atopic dermatitis) attending the Sheffield Children's Hospital, and to assess potential allergens that might elicit allergic contact dermatitis. Patients and methods. We analysed retrospectively the patch test results in 110 children aged between 2 and 18 years, referred to a contact dermatitis clinic between April 2002 and December 2008. We looked at the percentages of relevant positive reactions in boys and girls, by age groups, and recorded the outcome of treatment following patch testing. Results. One or more positive allergic reactions of current or past relevance was found in 48/110 children (44%; 29 females and 19 males). There were 94 allergy‐positive patch test reactions in 110 patients: 81 had a reaction of current or past relevance, 12 had a reaction of unknown relevance, and 1 had reaction that was a cross‐reaction. The commonest allergens with present or past relevance were medicaments, plant allergens, house dust mite, nickel, Amerchol® L101 (a lanolin derivative), and 2‐bromo‐2‐nitropropane‐1,3‐diol. However, finding a positive allergen was not associated with a better clinical outcome. Conclusions. We have shown that patch testing can identify relevant allergens in 44% of children with eczema. The commonest relevant allergens were medicament allergens, plant allergens, house dust mite, nickel, Amerchol® L101, and 2‐bromo‐2‐nitropropane‐1,3‐diol. Patch testing can be performed in children as young as 2 years with the proper preparation.     

Patch testing with the European baseline series fragrance markers: a 2016 update

Fragrance contact allergy is a common cause of allergic skin reactions that can cause eczema. Contact allergy can develop by repeated skin exposure to allergens over time. Fragrance contact allergy is diagnosed by patch testing (applying known allergens to the skin to assess for reactions). In the EU, cosmetic products are regulated to limit the exposure to known allergens. Furthermore, there is a requirement to label cosmetic products that contain any of 26 known individual fragrance allergens to help consumers avoid those allergens to which they are allergic. In most dermatology departments in the UK, instead of patch testing to all 26 individual fragrance allergens, fragrance contact allergy is diagnosed by patch testing to 4 screening markers: Fragrance Mix I, Fragrance Mix II, Myroxylon pereirae and hydroxyisohexyl 3‐cyclohexane carboxaldehyde. In this study, the authors reviewed 2084 records of patients with eczema who underwent patch testing to all the individual fragrance allergens, as well as the screening markers of fragrance allergy, to find out the proportion of actual fragrance contact allergy detected by testing only to the screening markers. They found that patch testing only to the screening markers detected 40.8% of patients with actual fragrance contact allergy (patients who were diagnosed with fragrance allergy when additionally tested with individual fragrance allergens). They also found that the majority of patients with fragrance contact allergy were not aware that they developed skin reactions upon exposure to fragrances. The authors concluded that the current screening markers used are not sufficient for the diagnosis of fragrance contact allergy.     

Patch testing in allergic contact dermatitis: is it useful to perform the cosmetic series in addition to the European standard series?

Background Cosmetics are the causative agents in 8–15% of patients suspected of having allergic contact dermatitis. Patch testing with standard series identifies 70–80% of the responsible allergens in all contact dermatitis; however, many important cosmetic‐related allergens may be missed by using standard series alone. Objective The aim of this study was to determine the value of using cosmetic series in addition to the European standard series in patients with suspected allergic contact dermatitis. Methods In this prospective study, 93 consecutive patients suspected of having allergic contact dermatitis were patch tested with the European standard series, and simultaneously with cosmetic series. Positive allergic reactions were further interpreted as clinically relevant or irrelevant. The clinically relevant reactions were subsequently stratified into three subgroups: (i) reactions only to allergen/allergens in the European standard series; (ii) reactions only to allergen/allergens in cosmetic series; and (iii) reactions both to allergen/allergens in the European standard and cosmetic series. Results A total of 74 positive reactions were observed in 93 patients. However, only 46 (62.2%) of the total positive reactions were found to be clinically relevant. Of all the clinically relevant positive reactions, 27 (58.7%) were caused by the allergens in the European standard series; 19 (41.3%) were caused by the allergens in cosmetic series. Of the 93 patients tested, 44 (47.3%) had at least one positive allergic reaction, 30 (68.2%) of whom had clinically relevance. Of the 30 patients with clinically relevant positive tests, 16 (53.3%) reacted only to allergens in the European standard series; nine (30%) reacted only to cosmetic series allergens; and five (16.7%) reacted both to the European standard and cosmetic series allergens. Among the 45 cosmetic series allergens tested, 15 (33.3%) gave positive reactions of which 14 (93.3%) of those were found to be clinically relevant. The clinically relevant cosmetic series allergens which were found to be over the critical incidence of 1% included methyldibromo glutaronitrile, Euxyl K400, and isopropyl myristate. Conclusion Patch testing with cosmetic series in addition to the European standard series increased the capability to detect the relevant allergen/allergens, particularly in patients with a suspicion of cosmetic allergy. However, it is not practical and cost‐effective to test those patients routinely with all 45 allergens in the cosmetic series. As the European baseline series which includes methyldibromo glutaronitrile is now widely used as the guideline minimum set of allergens for routine diagnostic patch test investigations, we additionally recommend Euxyl K400 and isopropyl myristate as the candidates for patch testing.     

European multicenter study of TRUE Test™, Panel 2

Panel 2 of the standardized, ready-to-apply patch test, the TRUE Test, has been evaluated on 808 patients with suspected contact dermatitis. The patients were tested with 11 different allergens and the negative control, and compared with corresponding allergens in pet. (or aq.) in Finn Chambers fixed with Scanpor. The TRUE Test, Panel 2 and the control were applied symmetrically on the upper back. Left/right application of the respective test varied at random. Most tests were removed after 48 h and evaluated after 72 or 96 h, according to generally accepted recommendations. There were positive test reactions to all 11 allergens tested in the patient group. The concordance of positive reactions (1+, 2+, 3+) was 63% between TRUE Test, Panel 2 and the control method; 17% of positive reactions occurred only with TRUE Test, Panel 2 and 20% only with the compared method. Approximately 75% of all positive test reactions were explained by the patients' present or past history. Irritant/questionable reactions occurred in the same frequency for the 2 methods. Such reactions were recorded in less than 1% of all patches applied. No late reactions were recorded.