The epidemic of methylisothiazolinone contact allergy in Europe: follow-up on changing exposures

Incidence of allergic contact dermatitis in Finland 1998-2021: A nationwide registry-based study

BACKGROUND

Allergic contact dermatitis (ACD) may be chronic and can cause distress, disability, and absence from work. Nationwide epidemiological studies of ACD are sparse.

OBJECTIVES

To use national registry data to study the incidence and aetiology of ACD in the working age population of Finland.

METHODS

Patient records from the years 1998-2021 were obtained from the Finnish Care Register for Health Care. Study subjects aged 18-65 years were selected on the basis of a diagnosis of ACD.

RESULTS

Total number of study subjects was 26 701. The incidence of ACD increased until 2016 after which it started to decrease. The increase was more marked in females and ACD was particularly common in women reporting reactions to cosmetics and other chemical products and in people of both sexes reacting to adhesives. The incidence 'ACD of unspecific cause' has decreased since 2016. The most commonly reported allergens were metals, followed by cosmetics. One fourth of subjects had ≥2 ACD diagnoses.

CONCLUSIONS

The incidence of ACD in working age subjects rose from 1998 to 2016, especially in females. However, the incidence has been decreasing since 2016. Our findings highlight the ongoing and even increasing burden of ACD among the working age population.

Current frequency of contact allergy to isothiazolinones (methyl-, benz- and octylisothiazolinone) across Europe

BACKGROUND

The use of methylisothiazolinone (MI) as a preservative in cosmetic products caused an alarming increase in MI contact allergy across Europe in the 2010s. This was followed by regulations of use with a total ban on leave-on (implemented in 2017) and reduced use concentrations in rinse-off cosmetics (2018).

OBJECTIVE

To follow-up on the prevalence of contact allergy to MI and the related benzisothiazolinone (BIT) and octylisothiazolinone (OIT) in consecutively patch-tested patients in Europe.

METHODS

A cross-sectional audit following the design of two previous audits on MI contact allergy from 1 May 2022 to 31 October 2022 included all patients patch tested with the European baseline series, including or supplemented with MI, BIT and OIT across 10 departments in eight European countries.

RESULTS

A total of 2554 patients were consecutively patch tested with the three isothiazolinones during the study period. The prevalence of MI and BIT contact allergy was 2.9% (95% confidence interval [CI]: 2.3%-3.7%; range 1.1%-5.8%) and 3.1% (95% CI: 2.4%-3.9%; range 0.0%-6.6%), respectively; that of OIT was 0.7% (95% CI: 0.4%-1.1%; range 0%-3.2%). Rinse-off cosmetic (73.3%) and leave-on cosmetic products (13.3%) were still associated with eliciting allergic contact dermatitis to MI.

CONCLUSION

We confirmed a positive impact of regulatory measures on the prevalence of MI contact allergy in Europe, which halved compared to 2015. However, our data suggest that consumers may still be exposed to older cosmetic products containing MI. BIT has superseded MI in causing contact allergy, despite not being allowed for use in cosmetic products.

Four-year Epidemiological Surveillance of the Spanish Registry of Research in Contact Dermatitis and Cutaneous Allergy: Current Situation and Trends

BACKGROUND

The epidemiological surveillance of contact dermatitis is one of the objectives of the Spanish Registry of Research in Contact Dermatitis and Cutaneous Allergy. Knowing whether the prevalence of positive tests to the different allergens changes over time is important for this monitoring process.

OBJECTIVES

To describe the various temporary trends in allergen positivity in the GEIDAC standard series from 2018 through December 31, 2022.

METHODS

This was a multicenter, observational trial of consecutive patients analyzed via patch tests as part of the study of possible allergic contact dermatitises collected prospectively within the Spanish Registry of Research in Contact Dermatitis and Cutaneous Allergy. The data was analyzed using 2 statistical tests: one homogeneity test (to describe the changes seen over time) and one trend test (to see whether the changes described followed a linear trend).

RESULTS

A total of 11327 patients were included in the study. Overall, the allergens associated with a highest sensitization were nickel sulfate, methylisothiazolinone, cobalt chloride, methylchloroisothiazolinone/methylisothiazolinone, and fragrance mix i. A statistically significant decrease was found in the percentage of methylisothiazolinone positive tests across the study years with an orderly trend.

CONCLUSIONS

Although various changes were seen in the sensitizations trends to several allergens of the standard testing, it became obvious that a high sensitization to nickel, methylchloroisothiazolinone/methylisothiazolinone and fragrances mix i remained. Only a significant downward trend was seen for methylisothiazolinone.

[Translated article] Four-year Epidemiological Surveillance of the Spanish Registry of Research in Contact Dermatitis and Cutaneous Allergy: Current Situation and Trends

BACKGROUND

The epidemiological surveillance of contact dermatitis is one of the objectives of the Spanish Registry of Research in Contact Dermatitis and Cutaneous Allergy. Knowing whether the prevalence of positive tests to the different allergens changes over time is important for this monitoring process.

OBJECTIVES

To describe the various temporary trends in allergen positivity in the GEIDAC standard series from 2018 through December 31, 2022.

METHODS

This was a multicenter, observational trial of consecutive patients analyzed via patch tests as part of the study of possible allergic contact dermatitises collected prospectively within the Spanish Registry of Research in Contact Dermatitis and Cutaneous Allergy. The data was analyzed using 2 statistical tests: one homogeneity test (to describe the changes seen over time) and one trend test (to see whether the changes described followed a linear trend).

RESULTS

A total of 11327 patients were included in the study. Overall, the allergens associated with a highest sensitization were nickel sulfate, methylisothiazolinone, cobalt chloride, methylchloroisothiazolinone/methylisothiazolinone, and fragrance mix i. A statistically significant decrease was found in the percentage of methylisothiazolinone positive tests across the study years with an orderly trend.

CONCLUSIONS

Although various changes were seen in the sensitizations trends to several allergens of the standard testing, it became obvious that a high sensitization to nickel, methylchloroisothiazolinone/methylisothiazolinone and fragrances mix i remained. Only a significant downward trend was seen for methylisothiazolinone.

Increased rates of contact allergy to selected preservatives in patients with allergic contact dermatitis in Turkey

BACKGROUND

Preservatives are a frequent cause of allergic contact dermatitis (ACD) and have caused numerous epidemics.

OBJECTIVES

The objective of this study is to determine the prevalence of preservative sensitivity, assess the change in the frequency of sensitivity, identify new preservatives with increased sensitivity rates, and evaluate the situation in Turkey by comparing our findings with current literature.

METHODS

A total of 201 patients diagnosed with ACD between 2018 and 2020, were patch tested with the European baseline series and additional seven preservative haptens. The change in the prevalence of sensitivity to each preservative hapten was investigated by comparing the data from the study conducted in our department between 2000 and 2004.

RESULTS

Results showed that 17.4% (n = 35) of the patients were positive to preservatives. Comparison with previous data from 2000 to 2004 revealed an increase in the frequency of sensitization. The most prevalent allergen was methyldibromo glutaronitrile (9.5%), followed by methylchloroisothiazolinone/methylisothiazolinone (6.5%), and methylisothiazolinone (5%).

CONCLUSION

The increase in preservative sensitivity in Turkey is the most remarkable finding. Although MDBGN was prohibited in cosmetic products, MCI/MI and MI are still widely used. Our findings suggest that awareness of preservative sensitivity should be increased and additional precautions should be taken, also in Turkey, regarding the use of preservatives.

Patch Testing Results From the Massachusetts General Hospital Occupational and Contact Dermatitis Clinic, 2017-2022

Background: Patch testing is gold standard for identifying the source of allergic contact dermatitis (ACD). Objective: To report patch testing results from the Massachusetts General Hospital (MGH) Occupational and Contact Dermatitis Clinic from 2017 to 2022. Methods: Retrospective analysis of patients referred to MGH for patch testing, 2017-2022. Results: In total, 1438 patients were included. At least 1 positive patch test (PPT) reaction was observed in 1168 (81.2%) patients and at least 1 relevant PPT reaction was observed in 1087 (75.6%) patients. The most common allergen with a PPT was nickel (21.5%), followed by hydroperoxides of linalool (20.4%) and balsam of Peru (11.5%). Sensitization rates statistically increased over time for propylene glycol and decreased for 12 other allergens (all P values <0.0004). Limitations: Retrospective design, single institution tertiary referral population, and variations in allergens and suppliers across the study period. Conclusion: The field of ACD is constantly evolving. Regular analysis of patch test data is crucial to identify emerging and diminishing contact allergen trends.

S2k-Leitlinie Diagnostik, Prävention und Therapie des Handekzems: S2k guideline diagnosis, prevention and therapy of hand eczema

Die S2k‐Leitlinie „Diagnostik, Prävention und Therapie des Handekzems (HE)“ gibt auf der Grundlage eines evidenz‐ und konsensbasierten Ansatzes konkrete Handlungsanweisungen und Empfehlungen für die Diagnostik, Prävention und Therapie des HE. Die Leitlinie wurde auf der Grundlage der deutschen Leitlinie „Management von Handekzemen“ aus dem Jahr 2009 und der aktuellen Leitlinie der European Society of Contact Dermatitis (ESCD) „Guidelines for diagnosis, prevention and treatment of hand eczema“ aus dem Jahr 2022 erstellt. Allgemeines Ziel der Leitlinie ist es, Dermatologen und Allergologen in der Praxis und Klinik eine akzeptierte, evidenzbasierte Entscheidungshilfe für die Auswahl sowie Durchführung einer geeigneten und suffizienten Therapie für Patienten mit Handekzemen zur Verfügung zu stellen. Die Leitlinie basiert auf zwei Cochrane‐Reviews zu therapeutischen und präventiven Interventionen beim HE. Die übrigen Kapitel wurden überwiegend basierend auf nicht systematischen Literaturrecherchen durch die Expertengruppe erarbeitet und konsentiert. Die Expertenkommission bestand aus Mitgliedern von allergologischen und berufsdermatologischen Fachgesellschaften und Arbeitsgruppen, einer Patientenvertretung und Methodikern. Im Rahmen einer Konsensuskonferenz am 15.09.2022 wurden die Vorschläge für die Empfehlungen und Kernaussagen unter Verwendung eines nominalen Gruppenprozesses konsentiert. Der strukturierte Konsensfindungsprozess wurde professionell moderiert. Die vorliegende Leitlinie hat eine Gültigkeit bis zum 22.02.2028.

S2k guideline diagnosis, prevention, and therapy of hand eczema

The consensus-based guideline "Diagnosis, prevention, and treatment of hand eczema (HE)" provides concrete instructions and recommendations for diagnosis, prevention, and therapy of HE based on an evidence- and consensus-based approach. The guideline was created based on the German guideline "Management von Handekzemen" from 2009 and the current guideline of the European Society of Contact Dermatitis (ESCD) "Guidelines for diagnosis, prevention, and treatment of hand eczema" from 2022. The general goal of the guideline is to provide dermatologists and allergologists in practice and clinics with an accepted, evidence-based decision-making tool for selecting and conducting suitable and sufficient therapy for patients with hand eczema. The guideline is based on two Cochrane reviews of therapeutic and preventive interventions for HE. The remaining chapters were mainly developed and consented based on non-systematic literature research by the expert group. The expert group consisted of members of allergological and occupational dermatological professional associations and working groups, a patient representative, and methodologists. The proposals for recommendations and key statements were consented by using a nominal group process during a consensus conference on September 15, 2022. The structured consensus-building process was professionally moderated. This guideline is valid until February 22, 2028.

Methyl(chloro)isothiazolinone contact allergy: a monocentric experience from Turkey

INTRODUCTION

Due to their ubiquitous use, isothiazolinones caused allergic contact dermatitis epidemics and their use was restricted by legal regulations.

OBJECTIVES

We aimed to evaluate demographic data, clinical findings, and patch test features of patients with methylisothiazolinone (MI) and/or methylchloroisothiazolinone(MCI) sensitivity in our study.

METHODS

This study is a bidirectional and cross-sectional study, between July 2020 and September 2021. A total of 616 patients, including prospective and retrospective populations, demographic data, clinical findings, and patch test results were reviewed. Patients' demographics, patch test results, allergen sources, presence of occupational contact, and the characteristics of dermatitis attacks were recorded.

RESULTS

A total of 50 patients with MI and MCI/MI sensitivity, 36 male (72%) and 14 female (28%), were included in our study. The overall prevalence of MI and MCI/MI between 2014 and 2021 was 8.4% (52/616) with two peak levels in 2015(21%) and 2021 (20%). A statistically significant relationship was found between shampoo use and facial involvement (p = 0.031), shower gel use and arm involvement (p = 0.027), wet wipe use and hand involvement (p = 0.049), detergent use and the pulps (p = 0.026) and the lateral aspects of fingers involvement (p = 0.048), water-based dye use and periungual involvement (p = 0.047).

CONCLUSION

Although legal regulations related to MI and MCI/MI cause a decrease in the frequency of their sensitivities were still common causes of allergic contact dermatitis.

Sensitization to isothiazolinones in the Spanish Contact Dermatitis Registry (REIDAC): 2019-2021 epidemiological situation

BACKGROUND

Current frequency and risk factors for sensitization to methylisothiazolinone (MI), methylchloroisothiazolinone/methylisothiazolinone (MCI/MI), benzisothiazolinone (BIT) and octylisothiazolinone (OIT) in Spain are not well known.

OBJECTIVES

To study the frequency of sensitization, risk factors and simultaneous sensitization between the four isothiazolinones.

MATERIALS AND METHODS

We analysed all 2019-2021 consecutive patients patch-tested with MI (0.2% aq.), MCI/MI (0.02% aq.), BIT (0.1% pet.) and OIT (0.1% pet) within the Spanish Contact Dermatitis Registry (REIDAC).

RESULTS

A total of 2511 patients were analysed. Frequencies of sensitization were: any isothiazolinone 15.7%, MI 6.8%, MCI/MI 4.8%, BIT 3.5% and OIT 0.5%. MI and MCI/MI sensitization was associated with being occupationally active, hand dermatitis, detergents and age over 40. BIT sensitization was associated with leg dermatitis and age over 40. About one in nine MI-positive patients were positive to BIT, whereas one in five BIT-positive patients were positive to MI.

CONCLUSIONS

Sensitization to MI, MCI/MI and BIT is still common in Spain, while sensitization to OIT is rare. Currently, sensitization to MI and MCI/MI seems to be occupationally related. Although its origin is unknown, sensitization to BIT is more frequent in patients aged over 40 years. Simultaneous sensitization between MI and BIT is uncommon.

North American Contact Dermatitis Group Patch Test Results: 2019-2020

Background: Patch testing is an important diagnostic tool for assessment of allergic contact dermatitis (ACD). Objective: This study documents the North American Contact Dermatitis Group (NACDG) patch testing results from January 1, 2019, to December 31, 2020. Methods: At 13 centers in North America, patients were tested in a standardized manner with a screening series of 80 allergens, and, as indicated, supplemental allergens. Results: Overall, 4121 patients were tested; 2871 (69.7%) had at least 1 positive/allergic patch test reaction and 2095 patients (51.2%) had a primary diagnosis of ACD. The most commonly positive allergens were nickel (18.2%), methylisothiazolinone (MI) (13.8%), fragrance mix (FM) I (12.8%), hydroperoxides of linalool (HPL) (11.1%), and benzisothiazolinone (BIT) (10.4%). Compared with that of 2017-2018, prevalence of top 20 allergens statistically increased for FM I, HPL, BIT, propolis, and hydroperoxides of limonene (3.5%). For the first time, MI positivity did not increase between reporting periods. Approximately one-fifth of patients (20.3%) had ≥1 clinically relevant reaction(s) to allergens/substances not on the NACDG series. Conclusions: The epidemic of MI contact allergy in North America may have reached a plateau. Patch testing using a robust screening series, and supplemental allergens as indicated, is necessary for comprehensive evaluation of ACD.

Patch test results in a Dutch paediatric population with suspected contact allergy: A retrospective cohort study

BACKGROUND

Allergic contact dermatitis (ACD) in paediatric patients is on the rise. Continuous identification of emerging allergens is of great importance to ensure accurate patch testing.

OBJECTIVES

To assess the frequency and relevance of contact sensitivity in children and adolescents and evaluate changes in sensitization rates in the last decade.

METHODS

All patients with suspected ACD who underwent patch testing at the Amsterdam University Medical Centers between 2015 and 2021 were included.

RESULTS

Of 439 patients tested with the European Baseline Series (EBS) and additional series, 334 (76%) patients had at least 1 positive reaction and 172 patients (39%) had 1 or more relevant positive reactions. If additional series would have been omitted, 20% of patients would have been underdiagnosed. Compared to patients tested between 1996 and 2013, reactions to metal allergens, isothiazolinones, methyldibromo glutaronitrile, carba mix, amerchol L-101, and benzophenone-4 were more frequently observed.

CONCLUSIONS

This study confirms the need for patch testing in paediatric patients suspected of having ACD. For accurate patch testing, it is advised to include additional series.

The European baseline series and recommended additions: 2023

The European baseline series was last updated in 2019. This article discusses the reasoning behind a further iteration of the series for 2023.

Decision making in next generation risk assessment for skin allergy: Using historical clinical experience to benchmark risk

Our aim is to develop and apply next generation approaches to skin allergy risk assessment that do not require new animal test data and better quantify uncertainties. Quantitative risk assessment for skin sensitisation uses safety assessment factors to extrapolate from the point-of-departure to an acceptable human exposure level. It is currently unclear whether these safety assessment factors are appropriate when using non-animal test data to derive a point-of departure. Our skin allergy risk assessment model Defined Approach uses Bayesian statistics to infer a human-relevant metric of sensitiser potency with explicit quantification of uncertainty, using any combination of human repeat insult patch test, local lymph node assay, direct peptide reactivity assay, KeratinoSens™, h-CLAT or U-SENS™ data. Here we describe the incorporation of benchmark exposures pertaining to use of consumer products with clinical data supporting a high/low risk categorisation for skin sensitisation. Margins-of-exposure (potency estimate to consumer exposure level ratio) are regressed against the benchmark risk classifications, enabling derivation of a risk metric defined as the probability that an exposure is low risk. This approach circumvents the use of safety assessment factors and provides a simple and transparent mechanism whereby clinical experience can directly feed-back into risk assessment decisions.

Novel insights into contact dermatitis

Contact dermatitis is a common disease, caused by repeated skin contact to contact allergens or irritants, resulting in allergic contact dermatitis (ACD) and/or irritant contact dermatitis. Attempts have been made to identify biomarkers to distinguish irritant and allergic patch test reactions, which could aid diagnosis. Some promising candidates have recently been identified, but verification and validation in clinical cases still need to be done. New causes of ACD are constantly recognized. In this review, 10 new contact allergens from recent years, were identified, several relating to anti-age products. Frequent allergens causing considerable morbidity in the population such as the preservative methylisothiazolinone (MI) have been regulated in EU. A significant drop in cases has been seen, while high rates are still occurring in other areas such as North America. Other frequent causes are fragrance allergens especially widely used terpenes and acrylates used in medical devises for control of diabetes. These represent unsolved problems. Recent advances in immunology have opened for a better understanding of the complexity of contact dermatitis, especially ACD. The disease may be more heterogenous that previous understood with several subtypes. With the rapidly evolving molecular understanding of the disease, the potential for development of new drugs for personalized treatment of contact dermatitis is considerable.

European patch test results with audit allergens as candidates for inclusion in the European Baseline Series, 2019/20 - Joint results of the ESSCAA and the EBSB working groups of the ESCD, and the GEIDACC

BACKGROUND

In 2019, a number of allergens (haptens), henceforth, 'the audit allergens,' were considered as potential additions to the European baseline series (EBS), namely, sodium metabisulfite, 2-bromo-2-nitropropane-1,3-diol, diazolidinyl urea, imidazolidinyl urea, Compositae mix II (2.5 or 5% pet), linalool hydroperoxides (lin-OOH), limonene hydroperoxides (lim-OOH), benzisothiazolinone (BIT), octylisothiazolinone (OIT), decyl glucoside, lauryl glucoside; Evernia furfuracea (tree moss), was additionally tested by some departments, too.

OBJECTIVES

To collect further data on patch test reactivity and clinical relevance of the audit allergens in consecutive patients across Europe.

METHODS

Patch test data covering the audit allergens in 2019 and 2020 were collected by those departments of the ESSCA testing these, as well as further collaborators from the EBS working group of the ESCD, and the Spanish GEIDAC. As patch test outcome, reactions between day (D) 3 and D5 were considered.

RESULTS

Altogether n=12403 patients were tested with any of the audit allergen. Positive reactions were most common to lin-OOH 1% pet. (8.74 (8.14-9.37)), followed by lin-OOH 0.5% pet., and lim-OOH 0.3% pet (5.41 (4.95-5.89)). Beyond these terpene hydroperoxides, BIT 0.1% pet. was the second most common allergen with 4.72 (4.2-5.28), followed by sodium metabisulfite 1% pet. (3.75 (3.32-4.23)) and Compositae mix 5% pet. (2.31 (1.84-2.87). For some allergens, clinical relevance was frequently difficult to ascertain.

CONCLUSIONS

Despite many positive patch test reactions, it remains controversial whether lin- and lim-OOH should be tested routinely, while at least the two preservatives BIT and sodium metabisulfite appear suitable. The present results are a basis for further discussion among the ESCD members and ultimately decision on their implementation into routine testing. This article is protected by copyright. All rights reserved.

Standard patch test results and clinical relevance: A cross-sectional study of 10-year retrospective experience

Background:

Allergic contact dermatitis (ACD) is a type IV hypersensitivity reaction, and The European Standard Series (ESS) Patch Test (PT) is widely used in determining the possible responsible allergens causing ACD. The dynamic nature of the industrial products, socioeconomic and environmental factors cause the frequency of common allergens to change over the years and among different regions.

Aims and Objectives:

This study aimed to retrospectively evaluate the results of ESS PT of our centre in the last decade, and determine the current spectrum of allergens and their clinical relevance.

Materials and Methods:

The data of patients who underwent ESS PT in our clinic between January 2010 and March 2020 were included in the study. The patient files were examined retrospectively. The clinical relevance was evaluated according to the COADEX system. Statistical analysis used: SPSS for Windows version 23.0 software program.

Results:

The data of 1037 patients [623 (60.1%) female, 414 (39.9%) male] were analysed. The mean age was 38.34 ± 14.55 years. The five most common allergens were nickel sulphate (23.1%), cobalt chloride (12%), potassium dichromate (9.5%), Fragrance mix II (7.3%) and balsam of Peru (5.7%). According to the COADEX coding system, current relevance was detected in 319 (49.3%) of 646 patients who had a positive reaction to any substance in the patch test.

Conclusion:

Our study showed that with increasing awareness in society, the tendency to avoid some well-known allergenic substances and consumer products causes changes in common allergens. These results prove the value of long-term surveillance of contact allergy.

Contact allergy to haptens in the Swedish baseline series: Results from the Swedish Patch Test Register (2010 to 2017)

BACKGROUND

Allergic contact dermatitis has considerable public health impact and causative haptens vary over time.

OBJECTIVES

To report the prevalence of contact allergy to allergens in the Swedish baseline series 2010 to 2017, as registered in the Swedish Patch Test Register.

METHODS

Results and demographic information for patients tested with the Swedish baseline series in 2010 to 2017 were analysed.

RESULTS

Data for 21 663 individuals (females 69%) were included. Females had significantly more positive patch tests (54% vs 40%). The reaction prevalence rates were highest for nickel sulfate (20.7%), fragrance mix I (7.1%), Myroxylon pereirae (6.9%), potassium dichromate (6.9%), cobalt chloride (6.8%), methylchloroisothiazolinone/methylisothiazolinone (MCI/MI; 6.4%), MI (3.7%), colophonium (3.5%), fragrance mix II (3.2%), and formaldehyde (3.2%). Myroxylon pereirae reaction prevalence increased from 5% in 2010 to 9% in 2017 and that for methyldibromo glutaronitrile from 3.1% to 4.6%. MCI/MI and MI reactions decreased in prevalence after 2014. Nickel reaction prevalence decreased among females aged 10 to 19 years.

CONCLUSIONS

Nickel remains the most common sensitizing agent, with reaction prevalence decreasing among females younger than 20 years. The changes in MCI/MI and MI reaction prevalence mirrored those in Europe. The register can reveal changes in contact allergy prevalence over time among patients patch tested in Sweden.

Trends in preservative allergy: Benzisothiazolinone emerges from the pack

BACKGROUND

Preservatives are used widely in cosmetic, household, and industrial products to prevent microbial growth and spoiling of the products. There has been a recent epidemic of contact allergy to methylisothiazolinone (MI).

OBJECTIVES

To establish emerging trends in preservative contact allergy as MI is replaced.

METHODS

We performed a retrospective study on consecutively patch-tested patients at our center from January 2011 to December 2019.

RESULTS

A total of 7846 consecutively patch-tested patients were included who were patch tested between January 2011 and December 2019. The prevalence of allergy to MI fell from a peak of 9.39% in 2013 to 1.98% in 2019. MI/methylchloroisothiazolinone (MCI) followed a similar trend, with a peak prevalence of 7.85% in 2014 and falling to 1.39% in 2018. The prevalence of contact allergy to benzisothiazolinone (BIT) has increased steadily increased in 2014 from 0.26% (confidence interval [CI] 0.03-0.93) to 3.42% (CI 2.43-4.66) in 2019.

CONCLUSIONS

Our data show a significant increase in the prevalence of contact allergy to BIT over the last 6 years, probably as a consequence of increased use in household products. It is essential to continue to look for emerging trends in contact allergy to enable prompt preventative measures to be taken.

Evolution of methylisothiazolinone sensitization: a Belgian multicentric study from 2014 to 2019

BACKGROUND

In the 2010s an epidemic of allergic contact dermatitis to methylisothiazolinone occurred in Europe. European authorities banned the use of methylisothiazolinone in leave-on cosmetics in 2017 and limited its use in rinse-off products in 2018.

OBJECTIVES

To investigate the sensitization rate to methylisothiazolinone in Belgium between January 2014 and December 2019, and to assess co-sensitizations to octylisothiazolinone and benzisothiazolinone in methylisothiazolinone -sensitized patients.

METHODS

A retrospective study of patch test results with methylisothiazolinone, octylisothiazolinone and benzisothiazolinone observed in patients attending five Belgian hospitals.

RESULTS

Overall, 560 of 10.029 patients (5.58%) had a positive patch test reaction to methylisothiazolinone, and its sensitization rate decreased from 7.9% in 2014 to 3.1% in 2019. Rinse-off cosmetics, paints and detergents were the most prevalent sensitization sources in recent years. Simultaneous reactions readily occurred to octylisothiazolinone, and, surprisingly, and increasingly, also to benzisothiazolinone.

CONCLUSIONS

Contact allergy to methylisothiazolinone in Belgium has reached a pre-epidemic level, reflecting the impact of recent regulatory measures. Leave-on cosmetics, in contrast to rinse-off products, have almost disappeared as sensitization sources in Europe. Paints and detergents also remain problematic. The remarkably high number of patients (co-) sensitized to benzisothiazolinone should be a focus of future research. This article is protected by copyright. All rights reserved.

Perivascular clusters of Th2 cells and M2 macrophages in allergic contact dermatitis to methylchloroisothiazolinone and methylisothiazolinone

BACKGROUND

Methylisothiazolinone (MI) and Methylchloroisothiazolinone (MCI) are among the most common skin sensitizers, yet the immunological events that occur during MCI/MI allergic contact dermatitis (ACD) are still poorly understood.

OBJECTIVES

To analyse dendrocytes, macrophage subtypes and T cells in skin during the elicitation phase of MCI/MI ACD.

METHODS

Thirteen patients with positive patch test reactions to MCI/MI (ACD group) and 11 individuals with negative patch test results were selected. Skin biopsies were only performed at 48 hours of patch testing. Immunohistochemistry was conducted to assess T cells, dendrocytes (Factor XIIIa), M1 (p-Stat1, CD68) and M2 (c-Maf, CD163) macrophages. Transcriptional analyses were performed for cytokines and related factors, and further compared to atopic dermatitis samples (n=4). Immunofluorescence assays addressed T cells location, along with IL-4 or IL-13, within the skin.

RESULTS

MCI/MI elicited dermal dendrocytes and macrophages, pronouncedly the M2 subtype. T cells, majorly CD4+ T cells, accumulated in the perivascular areas. Similarly, abundant IL-4 protein was detected in these areas. There was an upregulation of IL-4 and IL-13 mRNA expression, a mild increase in IFNG mRNA levels and a down-regulation of RORC in the ACD group. Immunofluorescence revealed dermal clusters of T cells co-localized with IL-4.

CONCLUSIONS

M2 macrophages and Th2 cells participate in the immunopathogenesis of MCI/MI ACD. Dermal dendrocytes and M2 macrophages may assist the formation of CD4+ T cells perivascular clusters. These findings render a mechanistic insight into the MCI/MI reaction. Further analysis at different timepoints of patch testing is required to fully comprehend this ACD kinetics.

Amended Safety Assessment of Methylisothiazolinone as Used in Cosmetics

The Expert Panel for Cosmetic Ingredient Safety (Panel) reassessed the safety of Methylisothiazolinone, which functions as a preservative in cosmetics. The Panel reviewed relevant animal and human data provided in this safety assessment, and data from the previously published safety assessments of Methylisothiazolinone, and concluded that Methylisothiazolinone is safe for use in rinse-off cosmetic products at concentrations up to 100 ppm (ie, 0.01%) and safe in leave-on cosmetic products when they are formulated to be nonsensitizing, which may be determined based on a quantitative risk assessment or similar methodology.

Contact dermatitis

Contact dermatitis (CD) is among the most common inflammatory dermatological conditions and includes allergic CD, photoallergic CD, irritant CD, photoirritant CD (also called phototoxic CD) and protein CD. Occupational CD can be of any type and is the most prevalent occupational skin disease. Each CD type is characterized by different immunological mechanisms and/or requisite exposures. Clinical manifestations of CD vary widely and multiple subtypes may occur simultaneously. The diagnosis relies on clinical presentation, thorough exposure assessment and evaluation with techniques such as patch testing and skin-prick testing. Management is based on patient education, avoidance strategies of specific substances, and topical treatments; in severe or recalcitrant cases, which can negatively affect the quality of life of patients, systemic medications may be needed.

What Is New in Occupational Allergic Contact Dermatitis in the Year of the COVID Pandemic?

PURPOSE OF REVIEW

This article aims to summarize some recent trends in occupational allergic contact dermatitis (ACD), including dermatitis related to pandemic-level personal protective equipment in healthcare workers, hazards patients may experience when working from home, and occupational perspectives on the recent American Contact Dermatitis Society (ACDS) allergens of the year and ACDS Core Allergen Series updates.

RECENT FINDINGS

Recent ACDS Allergens of the Year may be particularly relevant to healthcare workers, including isobornyl acrylate, which is present in glucose sensors and propylene glycol present in hand cleansers and disinfectants. Lavender, limonene, and linalool, all of which are new additions to the ACDS Core Allergen Series, have been reported as causes for occupational ACD in massage therapists and aromatherapists. Isothiazolinone allergy continues to rise in both consumer and occupational settings. Finally, the COVID-19 pandemic has resulted in a wave of occupational ACD in healthcare workers to personal protective equipment, and revealed new potential allergens for individuals working from home. Occupational allergic contact dermatitis continues to exert a significant occupational disease burden. Remaining aware of the current trends in allergens may allow for earlier recognition, diagnosis, and treatment, subsequently helping our patients to work in healthier and safer environments.

Contact allergy and allergic contact dermatitis from benzalkonium chloride in a tertiary dermatology center in Melbourne, Australia

BACKGROUND

Benzalkonium chloride (BAK) is a quaternary ammonium compound that is used widely as an antiseptic and preservative. It is a strong irritant and considered a weak sensitizer.

OBJECTIVE

To analyze the temporal trend of BAK sensitization and the demographics of sensitized patients.

METHODS

We conducted a single-center retrospective study of 7390 patients who were patch tested with BAK between January 1, 2003 and December 31, 2019.

RESULTS

Of the 7390 patients who were patch tested to BAK, 108 (1.5%) had a positive reaction, with 21 reactions deemed clinically relevant (0.3% of total patch tested) and a further 5 doubtful reactions deemed clinically relevant, resulting in a total of 26 relevant reactions (0.4% of total patch tested). Common sources of exposure were ophthalmic drops (30.8%), topical antiseptic preparations (26.9%), cosmetics (15.4%), disinfectant solutions (11.5%), hand sanitizers (11.5%), and hand washes (7.7%). One fifth of patients with relevant reactions were health care workers. There has been a dramatic increase in the number of positive reactions since 2017, for reasons not totally clear.

CONCLUSION

Contact allergy (CA) and allergic contact dermatitis (ACD) in response to BAK are now increasing at our center. Awareness of this trend is important, given that the coronavirus disease 2019 (COVID-19) pandemic is likely to further expose people to BAK.

Contact allergy to polyhexamethylene biguanide (polyaminopropyl biguanide)

Background

Polyaminopropyl biguanide (INCI name) and polyhexamethylene biguanide (PHMB) are polymeric biguanides. PHMB is a broad‐spectrum antimicrobial substance used as a preservative in many products. Due to our limited knowledge on PHMB contact allergy frequency and the fact that cases of allergic contact dermatitis to PHMB might be missed, we have included PHMB as a screening allergen since 2016.

Objective

To report the prevalence of positive patch test reactions to PHMB as a screening allergen in patients with suspected allergic contact dermatitis.

Methods

A retrospective analysis of 1760 patch tested patients from July 2016 to December 2018 was performed. Polyaminopropyl biguanide 2.0% aqua was included in the extended Malmö baseline series during the study period.

Results

Of all patients, 1204 (68.4%) were female. Positive patch test reactions were reported in 19 patients (1.1%). The most common sites of lesions were face, head, and neck (52.6%). There was a significant correlation between concomitant reactions to PHMB and other cosmetic‐related allergens.

Conclusion

The prevalence of positive reactions to PHMB was higher than that previously reported. Patch testing with PHMB should be performed in patients with dermatitis who have lesions on the face, head, and neck.

Hairdressers' occupational skin diseases in the Finnish Register of Occupational Diseases in a period of 14 years

BACKGROUND

Hairdressers have a high risk of occupational contact dermatitis caused by exposure to wet work and allergens in hairdressing chemicals.

OBJECTIVES

To examine the distribution of diagnoses of occupational skin diseases (OSDs) and their main causes in hairdressers based on a national register data on occupational diseases.

METHODS

We retrieved cases of recognized OSDs in hairdressers from the Finnish Register of Occupational Diseases (FROD) in years 2005-2018.

RESULTS

During the 14-year period, a total of 290 cases of recognized OSD in hairdressers were registered in the FROD. Allergic contact dermatitis (ACD) was diagnosed in 54%, irritant contact dermatitis in 44%, and contact urticaria (CU) in 5% of them. ACD was most commonly caused by hair dye products and their ingredients (N = 57), persulfates (N = 35), and preservatives (N = 35; mainly isothiazolinones). Acrylates emerged as hairdressers' occupational contact allergens (N = 8) probably due to introduction of structure nails into hair salons. Persulfates was the most common cause of CU.

CONCLUSIONS

ACD was the most common OSD in hairdressers. Our analysis confirms that preservatives are important causes of ACD in hairdressers in addition to hair dye products and persulfates. Acrylates emerged as hairdressers' occupational contact allergens, but contact allergy to perming agents remained rare.

The epidemic of contact allergy to methylisothiazolinone-An analysis of Danish consecutive patients patch tested between 2005 and 2019

BACKGROUND

In 2005, methylisothiazolinone (MI) was allowed as a stand-alone preservative in cosmetics. This resulted in an epidemic of allergic contact dermatitis to MI, mainly affecting women exposed to leave-on cosmetics. Consequently, a regulation of Annex V in the European Union in 2017 banned the use of MI in leave-on cosmetics and reduced the allowed concentration in rinse-off products.

OBJECTIVE

To analyze the temporal trends in contact allergy to MI in Danish patients in relation to key events including European regulations over time.

METHODS

A retrospective study of consecutive patients patch tested with methylisothiazolinone from 2005 to 2019. Demographics and clinical characteristics in terms of MOAHLFA (male, occupational, atopic dermatitis, hand dermatitis, leg dermatitis, facial dermatitis and age >40 years), sources of exposure, and clinical relevance were analyzed in relation to key historical events.

RESULTS

Three hundred eighty of 12 494 patients (3.0%, 95CI: 2.7-3.4%) tested from 2005 to 2019 were sensitized to MI. An increasing trend in the prevalence of MI contact allergy from 2005 to 2019 (P < .01) was observed, although a decline in the absolute number of patch-test positive patients was seen from 2013 and onward. A reduction in leave-on cosmetics as a source of exposure was observed following the legislative ban in 2017, from 24.8% from in 2010 to 2013 to 6.2% in 2017 to 2019 (P < .01).

CONCLUSION

The epidemic of MI contact allergy is declining in absolute terms, although the prevalence in the patch-tested population has not returned to its pre-epidemic levels. The legislative regulation of MI in 2017 has been effective in terms of leave-on cosmetics as a source of exposure in MI allergic patients. The process of post-marketing risk assessment of contact allergens in the European Union needs improvement.

Patch test results with the European baseline series and additions thereof in the ESSCA network, 2015-2018

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.

Methylchloroisothiazolinone/methylisothiazolinone and methylisothiazolinone contact allergy: A 24-year, single-center, retrospective cohort study from Turkey

BACKGROUND

Methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) and MI allergy caused a global epidemic during the period 2010 to 2015, reaching its peak in 2013/14.

OBJECTIVE

To investigate the characteristics of MCI/MI and MI allergy in Turkey over 24 years.

METHODS

A total of 2310 patients patch tested between 1996 and 2019 with MCI/MI 0.01% aq. or MCI/MI 0.02% aq., with or without MI 0.2% aq., were analyzed.

RESULTS

The overall prevalence of contact sensitization was 3.3% (n = 77) with a peak level of 16.4% in 2015. The prevalence gradually decreased thereafter, but was still high (6.5%) in 2019. Seventy-three patients had clinically relevant sensitizations. MI could detect clinically relevant sensitizations in all seven patients with a negative patch test reaction to MCI/MI 0.02%. Non-occupational allergic contact dermatitis (ACD) was most frequently seen, mainly in women, with hand/face eczema from rinse-off or leave-on cosmetics, such as wet wipes. Occupational ACD was mainly seen among men with airborne eczema from wall paints in house painters, or with hand eczema from hair gel/wax in men's barbers.

CONCLUSIONS

The prevalence of MCI/MI and MI sensitization in Turkey following the peak in 2015 is still high. This is probably due to the currently allowed level of 100 ppm for MI in rinse-off cosmetics. This needs to be urgently reduced.

In vivo demonstration of immunologic cross-reactivity to octylisothiazolinone in patients primarily and strongly sensitized to methylisothiazolinone

BACKGROUND

Notwithstanding that concomitant exposure to different isothiazolinone derivatives may result in concomitant sensitization, clinical and animal studies have suggested cross-reactivity between these derivatives, notably between methylisothiazolinone (MI) and octylisothiazolinone (OIT).

OBJECTIVE

To investigate if patients sensitized to MI show cross-reactions to OIT and/or to benzisothiazolinone (BIT) by applying the concept of the re-test method.

PATIENTS AND METHODS

From March to October 2019 consecutive patients were patch tested with MI 0.2% aqueous in duplicate at the two lower corners of both shoulder blades. Patients sensitized to MI, but not to OIT 0.1% petrolatum (pet.) nor to BIT 0.1% pet., were re-tested, 2 months later, with the latter two derivatives at the skin sites where the MI reactions had fully disappeared.

RESULTS

Of 116 patients, 15 (13%) were sensitized to MI, eight of these not sensitized to BIT nor to OIT. Of these, seven patients, all (very) strongly sensitized to MI, were re-tested: five patients showed positive patch test reactions to OIT 0.1% pet.; one patient to OIT 0.1% pet. and BIT 0.1% pet.; and one other patient showed no reactions.

CONCLUSION

This study suggests that patients primarily and strongly sensitized to MI may show immunologic cross-reactions to OIT, and to a far lesser extent to BIT.

Contact Allergy-Emerging Allergens and Public Health Impact

Contact allergy (sensitisation) and allergic contact dermatitis (ACD) resulting from it have a considerable public health impact. For the present review, all pertinent articles were systematically searched via Medline and Web of Science™; additionally, all available issues of the journals "Contact Dermatitis" and "Dermatitis" were manually searched, covering the years 2018-2019, thereby extending and re-focusing a previous similar review. New allergens, or previously described allergens found in a new exposure context or of other current importance, are described in sections according to substance classes, e.g., metals, preservatives, fragrances. As a common finding in many investigations, a lack of information on product composition has been noted, for instance, regarding a newly described allergen in canvas shoes (dimethylthiocarbamylbenzothiazole sulfide) and, most notably, absence of co-operation from manufacturers of glucose-monitoring devices and insulin pumps, respectively. These latter devices have been shown to cause severe ACD in a considerable number of diabetic patients caused by the liberation of isobornyl acrylate and N,N'-dimethylacrylamide, respectively, as demonstrated by an international collaboration between dermatologists and chemists. Improved and complete ingredient labelling for all types of products, and not just cosmetics, must be put on the legislative agenda.

[Toxicological risk assessment using the example of potential contact sensitization to resorcinol]

Resorcinol is a frequently used hair dye, whose quantitative risk assessment (QRA) for hair color products is presented in this review as an example to assess its skin sensitization risk after topical application. Its purpose is to determine the maximum concentration that can be used without expecting skin sensitization to occur. The focus is to prevent the de novo development of a contact allergy. Epidemiological data which are provided via dermatological surveillance, e.g., by the IVDK (Information Network of Departments of Dermatology) in Germany, are an important source of information that help to assess the quality and the effectivity of the QRA.