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Background: Clinical surveillance of the prevalence of contact allergy in consecutively patch tested patients is a proven instrument to continually assess the importance of contact allergens (haptens) assembled in a baseline series., Objectives: To present current results from the European Surveillance System on Contact Allergies, including 13 countries represented by 1 to 11 departments., Methods: Anonymized or pseudonymized patch test and clinical data from various data capture systems used locally or nationally as transferred to the Erlangen data centre were pooled and descriptively analysed after quality control., Results: In the 4 years (2015-2018), data from 51 914 patients patch tested with the European baseline series (EBS) of contact allergens were analysed. Contact allergy to nickel was most frequent (17.6% positive), followed by contact allergy to fragrance mix I (6.9%), methylisothiazolinone (MI; 6.2%), and Myroxylon pereirae resin (balsam of Peru; 5.8%)., Conclusions: While the prevalence of MI contact allergy decreased substantially following regulatory intervention, the persistently high levels of allergy to metals, fragrances, other preservatives, and rubber chemicals point to problems needing further research and, potentially, preventive efforts. Results with national additions to the baseline series provide important information on substances possibly to be considered for inclusion in the EBS., (© 2020 The Authors. Contact Dermatitis published by John Wiley & Sons Ltd.)

The present guideline summarizes all aspects of patch testing for the diagnosis of contact allergy in patients suspected of suffering, or having been suffering, from allergic contact dermatitis or other delayed-type hypersensitivity skin and mucosal conditions. Sections with brief descriptions and discussions of different pertinent topics are followed by a highlighted short practical recommendation. Topics comprise, after an introduction with important definitions, materials, technique, modifications of epicutaneous testing, individual factors influencing the patch test outcome or necessitating special considerations, children, patients with occupational contact dermatitis and drug eruptions as special groups, patch testing of materials brought in by the patient, adverse effects of patch testing, and the final evaluation and patient counselling based on this judgement. Finally, short reference is made to aspects of (continuing) medical education and to electronic collection of data for epidemiological surveillance., (© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Many key ingredients of hair cosmetics (in particular, dyes, bleaches, and hair-styling agents) are potent (strong to extreme) contact allergens. Some heterogeneity is apparent from published results concerning the range of allergens for which patch testing is important. The objective of the present review was to collect information on the current practice of using 'hair cosmetic series', and discuss this against the background of evidence concerning consumer/professional exposure and regulatory aspects to finally derive a recommendation for a 'European hair cosmetic series'. The methods involved (i) a survey targeting all members of the COST action 'StanDerm' (TD1206) consortium, (ii) analysis of data in the database of the European Surveillance System on Contact Allergies (ESSCA), and (iii) literature review. Information from 19 European countries was available, partly from national networks, and partly from one or several departments of dermatology or, occasionally, occupational medicine. Apart from some substances being tested only in single departments, a broad overlap regarding 'important' allergens was evident. Some of the substances are no longer permitted for use in cosmetics (Annex II of the Cosmetics Regulation). An up-to-date 'European hair cosmetics series', as recommended in the present article, should (i) include broadly used and/or potent contact allergens, (ii) eliminate substances of only historical concern, and (iii) be continually updated as new evidence emerges., (© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Methylchloroisothiazolinone (MCI) and methylisothiazolinone (MI) are the active ingredients in commonly used preservative systems (e.g. Kathon CG(®)). MCI/MI is present in the European baseline patch test series at 100 ppm aq. Since 1986, 200 ppm (dose 0.006 mg/cm(2)) has been used in Sweden without causing skin irritation. Centres in Spain, the United Kingdom and Ireland have also used 200 ppm in their baseline series., Objectives: To find the optimal patch test concentration for MCI/MI., Materials and Methods: MCI/MI 100 ppm aq. and MCI/MI 200 ppm aq. were simultaneously patch tested in 3300 consecutively tested dermatitis patients at eight European patch test clinics and one US patch test clinic. With the Finn Chambers(®) technique (diameter 8 mm), 15 µl was micropipetted on to the filter paper in the chamber. The corresponding volume for Van der Bend(®) chambers was 20 µl, and that for IQ Chambers(®) was 25 µl., Results: Contact allergy to MCI/MI at 100 and 200 ppm was found in 1.2% and 2.1% of patients, respectively (p < 0.001)., Conclusions: MCI/MI 200 ppm aq. (dose 0.006 mg/cm(2) ) diagnoses significantly more contact allergy than the presently used concentration of 100 ppm (dose 0.003 mg/cm(2)), without resulting in more adverse reactions. MCI/MI at 200 ppm should therefore be considered for inclusion in the European baseline test series., (© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Negative patch test results with fragrance allergy markers in the European baseline series do not always predict a negative reaction to individual fragrance substances., Objectives: To determine the frequencies of positive test reactions to the 26 fragrance substances for which labelling is mandatory in the EU, and how effectively reactions to fragrance markers in the baseline series predict positive reactions to the fragrance substances that are labelled., Methods: The records of 1951 eczema patients, routinely tested with the labelled fragrance substances and with an extended European baseline series in 2011 and 2012, were retrospectively reviewed., Results: Two hundred and eighty-one (14.4%) (71.2% females) reacted to one or more allergens from the labelled-fragrance substance series and/or a fragrance marker from the European baseline series. The allergens that were positive with the greatest frequencies were cinnamyl alcohol (48; 2.46%), Evernia furfuracea (44; 2.26%), and isoeugenol (40; 2.05%). Of the 203 patients who reacted to any of the 26 fragrances in the labelled-fragrance substance series, only 117 (57.6%) also reacted to a fragrance marker in the baseline series. One hundred and seven (52.7%) reacted to either fragrance mix I or fragrance mix II, 28 (13.8%) reacted to Myroxylon pereirae, and 13 (6.4%) reacted to hydroxyisohexyl 3-cyclohexene carboxaldehyde., Conclusions: These findings confirm that the standard fragrance markers fail to identify patients with contact allergies to the 26 fragrances., (© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Limonene is a common fragrance terpene that, in its pure form, is not allergenic or is a very weak allergen. However, limonene autoxidizes on air exposure, and the oxidation products can cause contact allergy. Oxidized R-limonene has previously been patch tested in multicentre studies, giving 2-3% positive patch test reactions in consecutive patients., Objectives: To investigate whether oxidized R-limonene 3.0% in petrolatum, with a stable concentration of the main haptens, limonene hydroperoxides (Lim-OOHs), could be a useful tool for the detection of contact allergy in an international setting., Methods: Oxidized R-limonene 3.0% (Lim-OOHs 0.33%) pet. was tested in 2900 consecutive dermatitis patients in Denmark, the United Kingdom, Singapore, Spain, Sweden, and Australia., Results: Overall, 5.2% (range 2.3-12.1%) of the patients showed a positive patch test reaction to oxidized R-limonene. Doubtful reactions were found in 7.0% of the patients (range 0-24%). Few irritant reactions were seen., Conclusions: Oxidized R-limonene at 3.0% pet. with a specified content of Lim-OOHs 0.33% is a standardized and useful tool for the detection of contact allergy in dermatitis patients. Many patients showing positive patch test reactions to oxidized R-limonene would not be informed of their fragrance allergy if this specific test had not been performed., (© 2013 John Wiley & Sons A/S.)

Background: The currently used patch test concentration for formaldehyde is 1.0% (wt/vol) in water. However, clinical experience and previous studies suggest that 1.0% might be insufficient for detecting an optimized number of clinically relevant cases of contact allergy to formaldehyde., Objectives: To validate earlier patch test results for comparison of 1% (wt/vol) and 2% (wt/vol) formaldehyde in water, and to investigate co-reactivity with quaternium-15., Materials and Methods: In 12 dermatology clinics, 3591 patients were routinely patch tested simultaneously with 2.0% (wt/vol) (0.60 mg/cm(2)) and 1.0% (wt/vol) (0.30 mg/cm(2)) formaldehyde. Micropipettes were used for delivering the exact dosage of the allergen., Results: Significantly more patients reacted to 2.0% formaldehyde than to 1.0% (3.4% versus 1.8%, p < 0.001). Overall, there were no sex differences between those reacting positively to 2.0% and 1.0%. Of 25 quaternium-15-positive patients, 4 (0.1%) reacted positively without reacting to formaldehyde., Conclusion: On the basis of the results of this multicentre study, as well as of previous studies, it can be suggested that 2.0% (wt/vol) in water formaldehyde should be used in routine patch testing in the baseline series., (© 2012 John Wiley & Sons A/S.)

Background: Currently, there is little data available on the reliability of patch testing in patients taking immunosuppressive agents other than systemic corticosteroids., Objectives: We present data from 38 patients who were patch tested whilst taking various immunomodulating agents to determine if positive reactions can be elicited. PATIENT/MATERIALS/METHODS: Between September 2006 and May 2009, 38 patients attending the St John's Institute of Dermatology were patch tested whilst taking immunosuppressive agents including azathioprine, ciclosporin, infliximab, adalimumab, etanercept, methotrexate, mycophenolate mofetil, and tacrolimus., Results: Positive patch test reactions of varying degrees and significance were elicited in: 2 of 10 patients on azathioprine; 5 of 11 patients on ciclosporin; 1 patient on ciclosporin and Fumaderm; 1 patient on infliximab; 1 patient on infliximab and methotrexate; 1 of 2 patients on adalimumab; 1 patient on etanercept and methotrexate; 3 of 4 patients on methotrexate; 1 of 3 patients on mycophenolate mofetil; and 1 patient on mycophenolate mofetil and tacrolimus. Negative patch test reactions occurred in 1 patient on azathioprine and ciclosporin; 1 patient on infliximab and azathioprine; and 1 patient on mycophenolate and ciclosporin., Conclusions: Positive patch test reactions can be elicited in patients taking azathioprine, ciclosporin, infliximab, adalimumab, etanercept, methotrexate, mycophenolate mofetil, and tacrolimus. However, it remains unclear what effect these immunosuppressive drugs may have on suppressing allergic patch test reactions and further studies should be carried out to determine the reliability of testing in these circumstances.

Background: Allergic contact dermatitis is common in hairdressers because of their exposure to chemicals used in hair dyes and permanent wave solutions. Atopic individuals are known to have a higher prevalence of leaving the profession due to morbidity associated with hand eczema., Objectives: To assess which chemicals are responsible for allergic contact dermatitis in hairdressers and whether the prevalence is the same according to atopy status., Methods: A total of 729 hairdressers who had been patch tested were retrospectively identified. Allergic reactions to relevant allergens from the extended European baseline series and hairdressing series were analysed against history of atopic eczema., Results: Of the total, 29.9% of patients had a current or past history of atopic eczema. The most frequent positive allergens from the European baseline series were nickel sulfate (32.1%) and p-phenylenediamine (19.0%) and from the hairdressing series were glyceryl monothioglycolate (21.4%) and ammonium persulfate (10.6%). There was no significant difference between people with or without a history of atopic eczema, except for fragrance mix I and nickel sulfate., Conclusions: We present findings from the largest cohort of hairdressers patch tested from a single centre. It is necessary to patch test hairdressers with dermatitis, regardless of a history of atopy. Strategies to reduce prevalence of allergic contact dermatitis are required.

Background: Positive patch test reactions to p-phenylenediamine (PPD) are common. PPD is used in oxidative hair dyes and is also present in dark henna temporary 'tattoos'. Cross-sensitization to other contact allergens may occur. Because subjects sensitized to PPD are at risk of clinically severe reactions upon hair dyeing, there is a need for 'current' prevalence data on PPD sensitization., Objectives: To compare PPD patch test results from dermatitis patients tested between 2003 and 2007 in 10 European patch test centres and to analyse the causes and determine relevance of positive PPD patch test reactions., Materials: Patch testing was performed using PPD (1% free base in petrolatum from Trolab (Almirall Hermal GmbH, Reinbeck, Germany) or Chemotechnique (Malmö, Sweden), equivalent to 0.090 mg/cm(2) in the TRUE test from MEKOS Laboratories AS). Statistical analysis was performed using the chi-squared test., Results: The weighted average prevalence was 4.6% among 21 515 patients. PPD sensitization occurred more often in centres located in Central and Southern Europe than in Scandinavian centres (odds ratio = 2.40; 95% confidence interval = 2.07-2.78). The overall proportion of positive patch test reactions to PPD that were registered as being of either current or 'past' relevance was high (weighted average 53.6% and 20.3%, respectively). Consumer hair dyeing was the most prominent cause of PPD sensitization (weighted average 41.8%). Furthermore, occupational hair dye exposure (10.6%) and cross-sensitization to textile dyes (12.6%) were frequently reported., Conclusions: PPD sensitization caused by exposure to hair dyes is frequent and remains a present problem for patients visiting contact dermatitis clinics, especially in patch test centres located in Central and Southern Europe.

Background: Active patch test sensitization is an uncommon phenomenon which may have undesirable consequences for those undergoing this gold-standard investigation for contact allergy., Objectives: To perform a retrospective analysis of the results of 241 subjects who were patch tested twice in a monocentre evaluating approximately 1500 subjects per year., Methods: Positivity to 11 common allergens in the recommended Baseline Series of contact allergens (European) was analysed: nickel sulphate; Myroxylon pereirae; fragrance mix I; para-phenylenediamine; colophonium; epoxy resin; neomycin; quaternium-15; thiuram mix; sesquiterpene lactone mix; and para-tert-butylphenol resin., Results: Only fragrance mix I gave a statistically significant, increased rate of positivity on the second reading compared with the first (P=0.011). This trend was maintained when separately analysing a subgroup of 42 subjects who had been repeat patch tested within 1 year; this analysis was done to minimize the potential confounding factor of increased usage of fragrances with a wide interval between both tests. To reduce the confounding effect of age on our data, we calculated expected frequencies of positivity to fragrance mix I based on previously published data from our centre. This showed a marked excess of observed cases over predicted ones, particularly in women in the age range 40-60 years., Conclusions: We suspect that active sensitization to fragrance mix I may occur. Similar published analysis from another large group using standard methodology supports our data.

Background: Alkyl ester quaternary ammonium compounds (ester quats) are used extensively in fabric rinse conditioners. It is important to document in the literature the outcome of historical studies that were performed to assess the risk of adverse skin effects associated with their use., Objectives: (1) To document the outcomes of historical studies performed to evaluate the skin sensitizing potential of two ester quats (the di-[hardened tallow fatty acid] ester of 2,3-dihydroxypropyl-trimethyl ammonium chloride [HEQ] and the dialkyl ester of triethanol ammonium methyl sulfate [TEA-Quat]) and (2) to demonstrate that these ester quats lack marked skin-sensitizing potential in humans, such that they do not present a risk of contact allergy for consumers who use fabric rinse conditioners., Methods: Each material was assessed in the human maximization test in a panel of 25 volunteers. Diagnostic patch testing was also performed with each material in a population of 239 patients undergoing routine patch testing for suspected allergic contact dermatitis. These data are also considered in the context of an exposure-based quantitative risk assessment., Results: Neither HEQ nor TEA-Quat was found to cause skin sensitization under the conditions of the human maximization test. No evidence of contact allergy to the materials was found among the relatively small population assessed by diagnostic patch testing., Conclusions: This study provides evidence that HEQ and TEA-Quat lack substantial skin-sensitizing potential in humans. Taken together with similar data for other ester quats, it suggests that compounds in this class are unlikely to be significant human contact allergens.

While the frequency of patch test reactivity to many cosmetic allergens has decreased over the last 20 years, we have previously shown that in our clinic, the patch test reactivity to p-phenylenediamine (PPD) has remained stubbornly high between 2.5% and 4.2% in the years when patch testing was performed with 1% PPD. Further retrospective analysis of the PPD patch test frequency over the last 6 years shows an increasing rate of PPD patch test frequency, showing an upward linear trend. This increasing trend cannot be fully explained by any increase in patch testing of Southern Asian patients or of sensitization caused by PPD exposure from 'temporary henna tattoos'. An alternative explanation may be the increasing use of permanent hair dyes.

The currently used 8% fragrance mix (FM I) does not identify all patients with a positive history of adverse reactions to fragrances. A new FM II with 6 frequently used chemicals was evaluated in 1701 consecutive patients patch tested in 6 dermatological centres in Europe. FM II was tested in 3 concentrations - 28% FM II contained 5% hydroxyisohexyl 3-cyclohexene carboxaldehyde (Lyral), 2% citral, 5% farnesol, 5% coumarin, 1% citronellol and 10%alpha-hexyl-cinnamic aldehyde; in 14% FM II, the single constituents' concentration was lowered to 50% and in 2.8% FM II to 10%. Each patient was classified regarding a history of adverse reactions to fragrances: certain, probable, questionable, none. Positive reactions to FM I occurred in 6.5% of the patients. Positive reactions to FM II were dose-dependent and increased from 1.3% (2.8% FM II), through 2.9% (14% FM II) to 4.1% (28% FM II). Reactions classified as doubtful or irritant varied considerably between the 6 centres, with a mean value of 7.2% for FM I and means ranging from 1.8% to 10.6% for FM II. 8.7% of the tested patients had a certain fragrance history. Of these, 25.2% were positive to FM I; reactivity to FM II was again dose-dependent and ranged from 8.1% to 17.6% in this subgroup. Comparing 2 groups of history - certain and none - values for sensitivity and specificity were calculated: sensitivity: FM I, 25.2%; 2.8% FM II, 8.1%; 14% FM II, 13.5%; 28% FM II, 17.6%; specificity: FM I, 96.5%; 2.8% FM II, 99.5%; 14% FM II, 98.8%; 28% FM II, 98.1%. 31/70 patients (44.3%) positive to 28% FM II were negative to FM I, with 14% FM II this proportion being 16/50 (32%). In the group of patients with a certain history, a total of 7 patients were found reacting to FM II only. Conversely, in the group of patients without any fragrance history, there were significantly more positive reactions to FM I than to any concentration of FM II. In conclusion, the new FM II detects additional patients sensitive to fragrances missed by FM I; the number of false-positive reactions is lower with FM II than with FM I. Considering sensitivity, specificity and the frequency of doubtful reactions, the medium concentration, 14% FM II, seems to be the most appropriate diagnostic screening tool.

In order to find sensitizers additional to the current fragrance mix (FM) a series of fragrance materials (series II) was evaluated in 6 dermatological centres in Europe. 11 of the test materials were essential oils, the remaining 7 being either mixtures of isomers or simple chemicals of frequent usage in the perfume industry. 1606 patients were consecutively tested with series II and 8% FM. Each patient was classified regarding a history of adverse reactions to scented products: certain, probable, questionable, none. Reactions to FM occurred most frequently in 11.4% of the subjects. The 6 materials with the highest reactivity after the FM were ylang-ylang oil (YY) I (2.6%), YY II (2.5%), lemongrass oil (1.6%), narcissus absolute (1.3%), jasmine absolute (1.2%) and sandalwood oil (0.9%). 48 (3.0%) of the patients reacted only to materials of series II and not to FM. 6.0% of 1606 patients gave a history of adverse reactions to fragrances which was classified as certain. This group reacted to FM only in 22.9%, to series II and FM in 15.6% and to series II only in 5.2%. 63.5% of the patients reacting to both FM and 1 of the materials of series II had some type of positive fragrance history, which was higher in comparison to those with isolated reactions to FM (46.2% of 121) or to series II, respectively, (45.8% of 48). However, this difference was not statistically significant. In conclusion, the materials of series II identified a further subset of patients with a fragrance problem, which would have been missed by the current FM as the single screening tool for patch testing.

The aim of this study was to determine the frequency of responses to selected fragrance materials in consecutive patients patch tested in 6 dermatological centres in Europe. 1855 patients were evaluated with the 8% fragrance mix (FM) and 14 other frequently used well-defined fragrance chemicals (series I). Each patient was classified regarding a history of adverse reactions to fragrances: certain, probable, questionable, none. Reactions to FM occurred in 11.3% of the subjects. The 6 substances with the highest reactivity following FM were Lyral (2.7%), citral (1.1%), farnesol P (0.5%), citronellol (0.4%), hexyl cinnamic aldehyde (0.3%), and coumarin (0.3%). 41 (2.2%) of the patients reacted only to materials of series I and not to FM. 6.6% of 1855 patients gave a history of adverse reactions to fragrances which was classified as certain. This group reacted to FM only in 41.1%, to series I and FM in 12.0% and to series I only in 7.2%. 74.3% of the 39 patients reacting to both FM and 1 of the materials of series I had any type of positive fragrance history, which was significantly higher in comparison to those with isolated reactions to series I (53.6% of 41), p = 0.04. The study identified further sensitizers relevant for patch testing of patients with contact dermatitis, of which Lyral is the most important single chemical.

Commercially available oak moss absolute patch test material has recently been shown to contain resin acids of the type found in colophony (colophonium). We wished to assess whether the high frequency of positive patch tests to oak moss absolute at this institute was likely to reflect significant contamination by resin acids. The rate of positive reactions to colophony among our oak moss-allergic patients patch tested during 1984-2000 was retrospectively investigated. 25395 patients were tested to the European standard series during this period and 1963 (7.7%) were allergic to the fragrance mix. 342 of these patients were allergic to oak moss absolute, of whom 73 (21.3%) were allergic to colophony. In comparison, 115 (13.4%) of 861 fragrance mix-positive but oak moss-negative patients were allergic to colophony (p = 0.0002, Fisher's exact test). This strongly statistically significant association between oak moss absolute and colophony shows only a small increase in rates of allergy to colophony in oak moss-positive patients. Thus we conclude that contaminating resin acids have not alone caused the high rate of sensitivity to oak moss.

This study investigated whether a corticosteroid mix containing tixocortol pivalate, budesonide, and hydrocortisone-17-butyrate could detect contact allergy to corticosteroids. 2 corticosteroid mixes, 1 with a high (mix I) and 1 with a low (mix II) concentration and the 3 individual constituents, each at 2 concentrations, were inserted into the standard series of 16 participating clinics. Tests were read on day (D) 3 or 4. 5432 patients were tested, and 110 (2.0%) had positive reactions to at least 1 of the 8 test preparations. Of the 8 preparations, mix I identified most allergic patients, followed by mix II, budesonide 0.10%, budesonide 0.002%, and tixocortol pivalate, both concentrations (1.0 and 0.10%) tracing the same number. With the mixes, 53.2-59.6% of tixocortol pivalate allergy was missed. 47 patients were allergic to either concentration of tixocortol pivalate, 25% of these only to 1.0% and another 25% only to 0.10%. Testing with mix I and tixocortol pivalate 0.10% picked up 98/110, testing with tixocortol pivalate 1.0% and 0.10% and budesonide 0.10% picked up 105/110. 3379 patients were read on both D3 or D4 as well as on D7. Without a late reading (D7), up to 30% of contact allergy to corticosteroid markers was missed.

Patch testing is the predominant method of establishing contact allergy. The present patch test technique is the result of a continuous process of development and improvement since its first application in the late 19th century. The perfect patch test should give no false-positive and no false-negative reactions. The ideal patch test should also cause as few adverse reactions as possible, particularly no patch test sensitization. Even though the history and examination of a patient with suspected allergic contact dermatitis will give clues to possible sensitizers, it is not sufficient to patch test only with initially suspected sensitizers; unsuspected sensitizers used for patch testing frequently turn out to be the real cause of the dermatitis. Fortunately, a small number of substances are considered to account for the majority of delayed hypersensitivity reactions. Therefore, generally 20-25 test preparations consisting of chemically defined compounds, mixes of allergens, and natural and synthetic compounds, are grouped into a standard test series. The requirements to be fulfilled by a sensitizer in a standard patch test series are discussed in this article. A procedure of investigations is proposed before a sensitizer is included in a standard series.

Immediate-type hypersensitivity to natural rubber latex (NRL) may be associated with chronic eczema, and it has recently been suggested that NRL should be used as a patch-test allergen. However, a standardized preparation does not exist, and experience of patch testing with this substance is extremely limited. The aims of our study were to investigate the patch-test response to different preparations of NRL amongst patients with suspected contact dermatitis. 608 patients were patch tested with a latex series which included wet and dry preparations of undiluted high-ammonia (HA) NRL and low-ammonia thiuram-containing NRL. Cutaneous reactions to 1 or more NRL patches were noted in 24 patients. None of these were strong allergic reactions (> +), and in 15 patients, the responses were only doubtful (?+). Positive patch tests were observed in 9 patients, and were probably due to concurrent thiuram allergy in 6. In the remaining 3 patients, the reactions had subsided by the 2nd reading and may have represented false positives. None of the patients showed consistent allergic reactions to all NRL patches, and most of the doubtful readings had resolved within 4 days, suggesting that they were irritant rather than weak allergic responses. Patch testing to dry HA latex was associated with the least number of reactions. We conclude that allergic patch test reactions to NRL are uncommon, and as reactions are usually weak and difficult to interpret, we suggest that patch testing with NRL should remain experimental until further studies have been undertaken.

In a retrospective case note analysis over a 4-year period, 0.9% of all patients tested with a standard patch test series (65 of 7600) were demonstrated to have clinically relevant responses to a sesquiterpene lactone (SQL) mix. Of these patients, 11 (17%) also had a diagnosis of chronic actinic dermatitis. This group made up 25% of all patients diagnosed as suffering from CAD in this 4-year period. These figures differ somewhat from those reported by our group in an initial 4-year period immediately following the introduction of the mix into our standard patch test series, when 1.5% of all patients tested had a clinically relevant response to the SQL mix, including 36% of all patients with a diagnosis of CAD. It is not uncommon for the prevalence of sensitivity to an allergen to be overestimated immediately following its introduction into routine testing. Possible reasons for our findings are discussed.

A major obstacle to the establishment of a protocol for in vivo irritant skin testing in humans is the apparent variability of responses between individuals. This study of the threshold response of normal human skin to a standard irritant (sodium lauryl sulfate 0.3-10%), in a group of 22 subjects, revealed a marked interindividual variation in their threshold reaction. The results demonstrate that this phenomenon does exist and that it will have to be allowed for in future human irritant test systems or assays.

We have reviewed our patch test results for preservative allergy from 1982 to 1993. 8 preservatives were included: formaldehyde, 2-bromo-2-nitropropane-1,3-diol (Bronopol(TM)), quaternium-15 (Dowicil 200TM), imidazolidinyl urea (Germall 115TM), diazolidinyl urea (Germall IITM), parabens, 5-chloro-2methyl-isothiazolin-3-one (Kathon CG(TM)) and 1,2-dibromo-2,4-dicyanobutane (one of the constituents of Euxyl K 400TM). Whereas the allergy rate to formaldehyde is quite stable, there is a slight increase in the imidazolidinyl urea allergy rate. Quaternium-15's rate is decreasing and 5-chloro-2-methyl-isothiazolin-3-one plus 2-methyl-isothiazolin-3-one's rate, after a rapid rise, seems to have stabilized. Although very important constituents of cosmetics, preservatives not only induce allergies on the face but also on the hands, and, as expected, the allergy rate in men and women generally differs. Among the 5 formaldehyde-releasers, there are some favoured simultaneous reactions: quaternium-15 and formaldehyde, and diazolidinyl urea and imidazolidinyl urea. Concomitant reactions between 1-bromo-2-nitropropane-1,3-diol and formaldehyde are not common, and those between 2-bromo-2-nitropropane-1,3-diol and diazolidinyl urea, and formaldehyde are not very common. This supports the hypothesis that allergic reactions to the Germalls are directed toward the initial molecule rather than to formaldehyde.

Changes to the European standard series which have taken place since the last officially recommended alterations in 1988, are explained. New to the series is the sesquiterpene lactone mix. The PPD black rubber mix and the quinoline mix have been replaced by single components; one of the p-hydroxybenzoates has been left out of the paraben mix. Ethylenediamine dihydrochloride has been dropped from the series.

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.

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.