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Background: Allergic contact dermatitis (ACD) caused by hexavalent chromium (Cr(VI)) is often severe and difficult to treat. The content of Cr(VI) in cement can be reduced by, for example, addition of iron(II) sulfate. Since 2005 the content of Cr(VI) in cement is regulated in the EU Directive 2003/53/EC and must not exceed 2 ppm. Since this regulation came into force, ACD caused by cement has markedly been reduced. Objective: To investigate Cr(VI) and total chromium content in samples of cement from countries within and outside the EU. Methods: The members of the International Contact Dermatitis Research Group (ICDRG) were invited to participate in the study with the aim to collect cement samples from geographically different areas. The content of Cr(VI) in the samples was estimated by the diphenyl carbazide spot test, atomic absorption spectroscopy was used to assess the total chromium content. Results: Forty-five cement samples were analyzed, containing amounts of Cr(VI) from <0.1 to >70 ppm. Twenty-one samples contained >2 ppm Cr(VI), 24 contained less. Four of 17 samples from within the EU contained >2 ppm Cr(VI), that is, higher amounts than stipulated in the EU directive, as compared with 17 samples from countries outside the EU. Conclusion: In countries outside the EU, significantly more cement samples contained >2 ppm Cr(VI).

Background: Nickel allergy is the most common contact allergy, and a nickel salt is, therefore, included in most baseline patch test series. In the baseline series of the International Contact Dermatitis Research Group and the American Contact Dermatitis Society, nickel sulfate hexahydrate (NSH) in petrolatum at 2.5% is included, whereas NSH at 5.0% is included in many other baseline series, such as the European and Swedish ones., Objective: The aim of the study is to investigate whether NSH at 5.0% detects significantly more contact allergy than NSH 2.5% when both preparations are tested simultaneously in consecutive dermatitis patients., Patients and Methods: Two thousand two hundred eighty-seven consecutive dermatitis patients were patch tested simultaneously with NSH in petrolatum at 2.5% and 5.0%. The allergy rates were compared for all clinics individually and combined using McNemar test, 2-sided., Results: Contact allergy to NSH 5.0% and 2.5% was found in 20.3% and 16.8%, respectively ( P < 0.0001). In 6 of 11 clinics, significantly more patients tested positive to the higher NSH concentration. For the 2 clinics in North America combined, significantly more patients tested positive to NSH 5.0%., Conclusions: The NSH preparation in the International Contact Dermatitis Research Group baseline patch test series should be considered to be changed from NSH 2.5% (1 mg NSH/cm 2 ) to 5.0% (2 mg NSH/cm 2 )., Competing Interests: The authors have no funding or conflicts of interest to declare., (Copyright © 2022 American Contact Dermatitis Society. All Rights Reserved.)

Background: In the early 1980s, a preservative containing a mixture of methylchloroisothiazolinone (MCI) and methylisothiazolinone (MI) in a ratio of 3:1 was introduced. This mixture (mix) has been patch tested at 100 ppm (0.01%) worldwide and at 200 ppm (0.02%) in Sweden since 1986 and also in the European baseline series since 2014., Objective: A new aqueous mix of MCI 0.015% and MI 0.2% was compared with patch testing with the 2 aqueous baseline preparations of MCI/MI 0.02% and MI 0.2%., Methods: Four thousand three hundred ninety-seven patients with dermatitis in 12 International Contact Dermatitis Research Group dermatology departments from 3 continents were patch tested simultaneously with the 3 preparations., Results: The frequency of positive patch tests to the allergens varied between 0% and 26.7% in the 12 test centers. The new mixture MCI/MI 0.215% in aqua (aq) detected significantly more patients with MCI/MI allergy than both MCI/MI 0.02% aq (P < 0.001) and MI 0.2% aq (P < 0.001) alone and combined., Conclusions: The results favor replacing the preparations MCI/MI 0.02% aq and MI 0.2% aq with the mixture MCI/MI 0.215% aq in the International Contact Dermatitis Research Group baseline series., Competing Interests: The authors have no funding or conflicts of interest to declare., (Copyright © 2021 American Contact Dermatitis Society. All Rights Reserved.)

Background: Mercaptobenzothiazole compounds are associated with allergic contact dermatitis caused by rubber products. Several screening substances have been used for patch testing., Objective: To compare the frequency of positive test reactions to a mercapto mix containing a higher concentration of 2-mercaptobenzothiazole with reactions to the combination of 2-mercaptobenzothiazole 2.0% and mercapto mix 2.0%., Methods: There were 7103 dermatitis patients in 12 International Contact Dermatitis Research Group dermatology departments who were patch tested with 2-mercaptobenzothiazole 2.0% petrolatum (pet.), mercapto mix 2.0% pet., and mercapto mix 3.5% pet., Results: Contact allergy to the 3 test preparations varied among the 12 centers: 2-mercaptobenzothiazole 2.0% pet. (0-2.4%), mercapto mix 2.0% pet. (0-4.9%), and mercapto mix 3.5% pet. (0-1.4%). 2-Mercaptobenzothiazole 2.0% and mercapto mix 2.0% detected a few more positive patients compared with mercapto mix 3.5%, but the difference was statistically insignificant (mercapto mix 2.0% pet., P = 1.0; 2-mercapto-benzothiazole 2.0% pet., P = 0.66)., Conclusions: Mercapto mix 3.5% pet. is not better than 2-mercaptobenzothiazole 2.0% and mercapto mix 2.0% by a difference that is significant. By using only 1 test preparation (mercapto mix 3.5%), an additional hapten could be tested. No cases of suspected/proven patch test sensitization were registered., Competing Interests: The authors have no funding or conflicts of interest to declare., (Copyright © 2021 American Contact Dermatitis Society. All Rights Reserved.)

Background: Fragrance mix II (FM II) is included in the baseline patch test series recommended by the International Contact Dermatitis Research Group (ICDRG). Hydroxyisohexyl 3-cyclohexene carboxaldehyde (HICC) is the most important sensitizer of the 6 fragrance materials included in FM II. Besides being a part of FM II, HICC is also tested separately in the ICDRG baseline series., Objectives: The aim of the study was to investigate the prevalence of contact allergy to FM II and HICC in 2012-2016 with a focus on simultaneous reactions and the percentage of missed contact allergy to HICC provided that only FM II had been tested., Patients and Methods: A total of 25,019 consecutive dermatitis patients in 13 dermatology clinics representing 12 countries in 5 continents were patch tested with FM II and HICC in the baseline series., Results: Contact allergy to FM II and HICC was found in 3.9% and 1.6%, respectively. For FM II, the frequency varied from 1.5% to 7.6% in different centers. The corresponding range for HICC was 0.2% to 3.6%. Simultaneous contact allergy to FM II and HICC was noted in 1.4% with the range 0.2% to 2.6%. Seventy-seven patients (0.31%) with contact allergy to HICC did not test positively to FM II. The range for missed HICC allergy by testing only FM II in the different centers would be 0.04% to 0.74%. The ratio between the contact allergy rates for FM II and HICC was similar for all centers, except for Montreal having significantly more contact allergy to FM II than to HICC., Conclusions: The frequency of missed contact allergy to HICC when testing only with FM II was less than 0.5%, therefore questioning the need to test HICC separately in the ICDRG baseline series.

Background: The International Contact Dermatitis Research Group increased the patch test concentration of formaldehyde from 1.0% aqueous (aq) to 2.0% aq (in 2011)., Objective: This study was designed to investigate the outcome of the decision., Methods: Consecutive dermatitis patients in 8 different clinics were patch tested with formaldehyde 1.0% aq and 2.0% aq. The test solutions were applied with a micropipette to the filter paper discs in the respective chamber., Results: A total of 2778 patients were tested with 1.0% aq and 2766 to 2.0% aq. Sixty-five patients (2.3%, calculated from 2766 tested, to 2.0% aq) had positive patch test reactions interpreted as contact allergy to formaldehyde. This is a rather low frequency. Of these 65, 46 were women (46/1703 [2.7%]) and 19 were men (19/1063 [1.8%]). Thirty-six reacted only to 2.0% aq, 21 patients reacted to both concentrations, and 8 patients reacted only to 1.0% aq. Significantly, more patients reacted to 2.0% aq compared with 1.0% aq (P < 0.001). There was no significant sex difference. A total of 0.8% irritant reactions were recorded to formaldehyde 2.0% aq and 0.1% to 1.0% aq., Conclusions: The increased formaldehyde patch test concentration to 2.0% aq revealed more formaldehyde contact allergy.

Background: Since the 1990s, gold has been recognized as an important contact allergen., Objectives: Based on our results with gold sodium thiosulfate (GST) in the TRUE Test patch test system in the baseline series, the aims of the study were to evaluate baseline testing with gold salts worldwide and to discuss relevance., Methods: Patients with positive patch test reactions to GST were questioned on exposure at day 7 reading., Results: In a 1-year period, 89 (18.5%) of 480 patients tested positive to GST, making this the most frequent contact allergy. The 89 patients comprised 18 males and 71 females. The reaction was considered relevant in 21%; this is a minimum figure because 2 patients were withdrawn because of unknown relevance and because clinical features suggestive of gold contact allergy at distant sites, such as the face, were not taken into account. Altogether, 88% had been exposed. Worldwide, the prevalence of gold sensitization ranges between 0.78% and 30.7%, and relevance, in larger studies, has been between 15% and 20% of patients. The use of earrings and the presence of dental gold were important sources of exposure., Conclusions: Because it may be difficult to diagnose gold allergy, screening may be recommended when history taken suggests gold exposure.

Background: Dose/area and reading paradigms for gold patch testing are controversial and not standardized worldwide., Objectives: The aims of this study were to determine the optimum patch test dose of gold sodium thiosulfate (GST) in a hydrogel (HYD) and to establish GST HYD safety/efficacy and further characterize normal morphology and time course of GST reactions., Methods: Twenty gold-allergic patients were patch tested with a dilution series of GST HYD and with GST 2% petrolatum (pet). Furthermore, this previously determined optimal dose was compared with GST 0.5% pet in 19 known-allergic and 216 consecutive subjects., Results: The optimal GST HYD dose was 0.075 mg/cm, not statistically different from GST 2% pet (P = 0.4795). Gold sodium thiosulfate HYD outperformed GST 0.5% pet in both known-allergic subjects (79% vs 63%, P = 0.2482) and consecutive subjects (30% vs 9%, P < 0.0001). Late reactions were common in consecutive patients with both HYD and pet. Significantly more persistent reactions were associated with GST HYD than with GST 0.5% pet., Conclusions: Gold sodium thiosulfate HYD 0.075 mg/cm is the optimal dose for diagnosis of gold contact allergy with GST. Gold sodium thiosulfate 0.5% pet yielded false-negatives in some patients, suggesting inadequate dose per centimeter squared. Late reads are normal, expected, and necessary for diagnosis of gold contact allergy in this cohort.

Background: The preservatives methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) and MI are well-known contact sensitizers. Recently, an increase in the contact allergy frequency for MI 0.2% aqueous (aq) has been seen in many European countries paralleled with an increase in MCI/MI allergy. Many of the MI-allergic patients do not react to MCI/MI 0.01% or 0.02% because the concentration of MI in these preparations is too low (25 and 50 ppm, respectively) to elicit a positive patch test reaction., Objectives: The aims of this study were to investigate the prevalence of contact allergy to MI in the participating clinics representing various countries all over the world, to assess how many additional individuals with contact allergy are found by testing MI 0.2% aq in parallel with MCI/MI 0.02%, and to assess the clinical relevance of MI and MCI/MI allergies., Patients and Methods: In 9 dermatology clinics representing 9 countries, 3865 consecutive patients with dermatitis were patch tested with MI 0.2% aq and in parallel with MCI/MI 0.02% aq, provisionally included into the baseline series. An assessment of clinical relevance in those allergic to MI was also made., Results: Contact allergy to MI was found in 284 patients (7.3%). The frequency of contact allergy varied from 0.8% to 10.9% in different centers. Simultaneous reactivity to 200 ppm of MCI/MI was found in 67.3% of the MI-positive patients. Contact allergy to MI alone without any simultaneous contact allergy to 200 ppm of MCI/MI was diagnosed in 93 patients (32.7%; 2.4% of all tested patients). The contact allergy to MI and/or MCI/MI could explain or contribute to dermatitis in more than 60% of the MI-allergic patients., Conclusions: Methylisothiazolinone of 2000 ppm needs to be patch tested on its own to not miss contact allergy.

Background: The preservative methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) is a well-known contact sensitizer. Historically, there have been different opinions on the optimal patch test concentration of MCI/MI, and both 0.01% and 0.02% aqueous (aq.) have been proposed. In 2011, based on literature reviews, it was recommended that the concentration of 0.02% aq. should be used in the international baseline series., Objectives: The aim of this study was to verify the recommendation from 2011 by comparing the patch test results from consecutive patch testing with MCI/MI 0.01% and 0.02% in clinics representing countries around the world., Patients and Methods: Two thousand seven hundred three consecutive patients with dermatitis in 8 dermatology clinics representing 8 countries were patch tested with MCI/MI 0.01% aq. and, in parallel with MCI/MI 0.02% aq., provisionally included in the baseline series., Results: Contact allergy to MCI/MI at 0.01% and 0.02% was found in 3.7% and 5.6% of the patients, respectively (P < 0.001)., Conclusions: Methylchloroisothiazolinone/MI 0.02% aq. (dose, 6 μg/cm) diagnoses significantly more contact allergy than 0.01% (dose, 3 μg/cm), without resulting in more adverse reactions. Methylchloroisothiazolinone/MI at 0.02% aq. should therefore be continuously used in the international baseline series.

The International Contact Dermatitis Research Group proposes a classification for the clinical presentation of contact allergy. The classification is based primarily on the mode of clinical presentation. The categories are direct exposure/contact dermatitis, mimicking or exacerbation of preexisting eczema, multifactorial dermatitis including allergic contact dermatitis, by proxy, mimicking angioedema, airborne contact dermatitis, photo-induced contact dermatitis, systemic contact dermatitis, noneczematous contact dermatitis, contact urticaria, protein contact dermatitis, respiratory/mucosal symptoms, oral contact dermatitis, erythroderma/exfoliative dermatitis, minor forms of presentation, and extracutaneous manifestations.

Background: Disperse dyes are well-known contact sensitizers not included in the majority of commercially available baseline series., Objective: To investigate the outcome of patch testing to a textile dye mix (TDM) consisting of 8 disperse dyes., Methods: Two thousand four hundred ninety-three consecutive dermatitis patients in 9 dermatology clinics were patch tested with a TDM 6.6%, consisting of Disperse (D) Blue 35, D Yellow 3, D Orange 1 and 3, D Red 1 and 17, all 1.0% each, and D Blue 106 and D Blue 124, each 0.3%. 90 reacted positively to the TDM. About 92.2% of the patients allergic to the TDM were also tested with the 8 separate dyes., Results: Contact allergy to TDM was found in 3.6% (1.3-18.2) Simultaneous reactivity to p-phenylenediamine was found in 61.1% of the TDM-positive patients. Contact allergy to TDM and not to other p-amino-substituted sensitizers was diagnosed in 1.2%. The most frequent dye allergen in the TDM-positive patients was D Orange 3., Conclusions: Over 30% of the TDM allergic patients had been missed if only the international baseline series was tested. Contact allergy to TDM could explain or contribute to dermatitis in over 20% of the patients. Textile dye mix should be considered for inclusion into the international baseline series.

Attempts to improve the formulations of topical products are continuing processes (ie, to increase cosmetic performance, enhance effects, and protect ingredients from degradation). The development of micro- and nanovesicular systems has led to the marketing of topical drugs and cosmetics that use these technologies. Several articles have reported improved clinical efficacy by the encapsulation of pharmaceuticals in vesicular systems, and the numbers of publications and patents are rising. Some vesicular systems may deliver the drug deeper in the skin as compared to conventional vehicles, or even make transdermal delivery more efficient for a number of drugs. Vesicular systems may also allow a more precise drug delivery to the site of action (ie, the hair follicles) and thereby minimize the applied drug concentration, reducing potential side effects. On the other hand, this may increase the risk of other side effects. Few case reports have suggested that microvesicle formulations may affect the allergenicity of topical products. This article gives an overview of the current knowledge about the topical use of microvesicular systems and the dermatoallergologic aspects.

Allergic contact dermatitis (ACD) from salicylates present in topical products is uncommon. Most publications about ACD from salicylates are case reports describing only a few patients. Cross-reactivity between salicylates is not commonly reported. This article describes allergic contact dermatitis from ethylhexyl salicylate used as an ultraviolet filter and fragrance compound and reviews the published literature on contact allergy to salicylates.