Kathon Research Articles

Contact dermatitis: Clinical practice findings from a single tertiary referral hospital, a 4-Year retrospective study

BackgroundIt is estimated that 20% of the general population is sensitized to some kind of contact allergen. Contact dermatitis is one of the major occupational diseases worldwide. This disease has a higher prevalence in the female gender and is more frequently observed in the third or fourth decade of life. The main objective of this study was to describe the main sociodemographic and clinical characteristics of patients with contact dermatitis treated in the Allergy Unit of the San Juan De Dios Hospital – Caja Costarricense de Seguro Social. MethodsClinical records of contact dermatitis outpatients from a single hospital were analyzed, in a 4-year retrospective observational study. ResultsAt the time of the patch testing, patients showed a mean age of 42.2 years. Disease frequency was higher in the female population (female/male ratio of 4.2:1) and in patients mostly dedicated to household workchores. Most patients presented several years of disease history, and the hands were the highest affected body part. Patch testing revealed that nickel sulfate, Cl+Me-Isothiazolinone (Kathon CG), and thimerosal were allergens regularly associated with contact dermatitis in the analyzed population. ConclusionsTo a great extent, sociodemographic and clinical characteristics identified in these patients resemble what is reported in other regions, including the Americas and worldwide. It is worth highlighting a high female proportion rate probably related to cultural aspects, a smaller percentage of irritant contact dermatitis that may be associated to institutional patient management, and a slight difference in the most common allergens when compared to other published studies.

Proinflammatory and regulatory mechanisms in allergic contact dermatitis caused by methylchloroisothiazolinone and methylisothiazolinone.

Methylchloroisothiazolinone (MCI) and methylisothiazolinone (MI) are the cause of an increasing number of contact allergies. Understanding the mechanisms by which MCI/MI induces proinflammatory and regulatory factors production is necessary to understand the outcome of allergic contact dermatitis (ACD). To evaluate the dysfunction of proinflammatory cytokines and regulatory factors in the positive MCI/MI patch test at the transcriptional and protein expression levels. Moreover, to analyse the cytokines production induced by MI in peripheral blood mononuclear cells (PBMCs). The selected patients had positive MCI/MI patch test results. The expression of proinflammatory factors was evaluated by q-PCR and immunochemistry at 48hours of positive MCI/MI patch test. The MCI/MI- or MI- induced secretion of IL-1β, TNF and IL-6 by PBMC was analysed by flow cytometry. The results showed a decreased TLR4 expression with upregulated IL6, FOXP3, IL10 and TGFβ mRNA expression as assessed by q-PCR at the site of the MCI/MI skin reaction. We detected increased protein levels of TLR4, FOXP3 and IL-10 in the dermis layer in the ACD reaction by immunocitochemistry. Moreover, MCI/MI induced proinflammatory cytokine production by PBMC through the NF-κB signalling pathway. Considering the altered innate immune response triggered by MCI/MI sensitization, these findings indicate that the regulatory process at the induction phase of ACD is a crucial mechanism. Given the increase in occupational and domestic exposure to MCI/MI, the underlying immunological mechanisms should be understood.

High rate of sensitization to Kathon CG, detected by patch tests in patients with suspected allergic contact dermatitis

BackgroundKathon CG, a combination of methylchloroisothiazolinone and methylisothiazolinone, is widely used as preservative in cosmetics, as well in household cleaning products, industrial products such as paints and glues. It has emerged as an important sensitizing agent in allergic contact dermatitis. ObjectivesThis study evaluated the reactivity to this substance in patients subjected to patch tests at the Dermatology Institute in Bauru, São Paulo from 2015 to 2017 and its correlation with other preservatives, the professional activity and location of the lesions. MethodsThe patients were submitted to standard series of epicutaneous tests, standardized by the Brazilian Group Studies on Contact Dermatitis. ResultsOut the 267 patients tested, 192 presented positivity to at least one substance and 29 of the patients (15.10%) presented reaction to Kathon CG, with predominance of the female gender (n=27); main professional activity associated with Kathon CG sensibilization was cleaning (17.24%), followed by aesthetic areas (13.79%) and health care (10.34%). The most prevalent sensitizations among the substances tested were nickel sulphate (56.3%), followed by cobalt chloride (23.4%), neomycin (18.2%), potassium dichromate (17.7%), thimerosal (14.5%), formaldehyde (13.2%), paraphenylenediamine (9.3%), and fragrance mix (8.3%). Study limitationsWe do not have data from patients that were submitted to patch test a decade ago in order to confront to current data and establish whether or no sensitization to Kathon CG has increased. ConclusionHigh positivity to Kathon CG corroborates the recent findings in the literature, suggesting more attention to concentration of this substance, used in cosmetics and products for domestic use.

Electrochemical oxidation of isothiazolinone biocides and their interaction with cysteine

This paper presents voltammetric studies on carbon electrodes (linear-sweep cyclic voltammetry and differencial pulse voltammetry) on the electrooxidation of methylisothiazolinone (MIT), Chloromethylisothiazolinone (CMIT) and 4,5-dichloro-2-octyl-4-isothiazolin-3-one (DCOIT). The oxidation products have been identified after electrolysis of the compounds using liquid-liquid extraction and gas chromatography coupled to mass spectrophotometry. The identified compounds for the three biocides correspond in all cases to two-electron processes, with opening of the ring. Adsorption processes were observed for CMIT. From the differential pulse voltammetric results a general reaction pathway is proposed in which the rate-determining step is a chemical reaction placed after the first partially irreversible electron transfer. The interaction of cysteine with MIT and CMIT was studied by differential pulse voltammetry in order to quantify them and the 1:3 mixture. The specificity of the interaction with cysteine and the low values of the peak potentials minimize the interferences. The quantification is made from the decrease of the oxidation signal of cysteine as the biocide concentration increases, being the method adequate for the study of usual cosmetic and household products.

Elimination of isothiazolinone biocides in reverse osmosis concentrate by ozonation: A two-phase kinetics and a non-linear surrogate model

Elimination of commercial Kathon biocide (methyl-isothiazolinone (MIT) and chloro-methyl-isothiazolinone (CMIT) mixture) by ozonation was investigated in real RO influent and concentrate. MIT and CMIT had different reactivities (second-order-rate-constants) with molecular ozone and OH. Ozonation of biocides followed an instantaneous phase (16.6 %–36.9 % contributions) and then a gradual phase (33.6 %–78.8 % contributions). Newly developed kinetics including both phases demonstrated that O3 oxidation contributed 25.6 %–39.8 % and <10 % of MIT and CMIT eliminations, respectively, and OH oxidation contributed 60.2 %–74.4 % and >90 % of MIT and CMIT eliminations, respectively. OH oxidation at the instantaneous phase accounted 15.7 %–37.9 % of total OH oxidation. Mass ratios of O3/DOC of 0.24 and 0.32 were needed for ∼80 % eliminations of MIT and CMIT in RO concentrate, respectively. The kinetics including both phases allowed a para-chlorobenzoic acid indicator model to predict MIT and CMIT elimination better than that including gradual ozonation only, with 58.9 %–96.0 % lower relative error. The attenuations of electron-donating-moiety indicated that O3 may preferentially react with chromophores through aromatic cleavage and electrophilic extraction, while •OH may non-selectively react with chromophores through predominant electrophilic addition. A surrogate model for biocide elimination by UVA254 loss was proposed to be nonlinear rather than linear, which reduced 31.8 %–71.3 % surrogating error.

Isothiazolinones in cleaning products: Analysis with liquid chromatography tandem mass spectrometry of samples from sensitized patients and market.

Methylchloroisothiazolinone (MCI) and methylisothiazolinone (MI) contact dermatitis is a severe problem. The high concentrations of these substances and other isothiazolinones such as benzisothiazolinone (BIT) and octylisothiazolinone (OIT) contained in cleaning products may cause allergic contact dermatitis in sensitized patients. To evaluate the exposure to isothiazolinones contained in cleaning products on the market and from sensitized patients, and to verify the accuracy of labeling. A total of 34 cleaning products were collected (17 supplied by sensitized patients and 17 bought randomly). Analysis was made of the concentrations of MI, MCI, BIT, and OIT using liquid chromatography tandem mass spectrometry (LC-MS/MS). MI and BIT were the components most frequently detected. Of all the products analyzed, 76.5% contained at least one isothiazolinone. Twelve products had an MI concentration above the permitted level for rinse-off cosmetics. Most of them were coming into direct contact with the skin in daily use. Mislabeling occurred in eight products. Some cleaning products with high concentrations of isothiazolinones may cause cutaneous symptoms in sensitized patients, especially in spray form. The labeling should be correct, also regarding the use of each article.

Development and Validation of an HPLC Method for Simultaneous Assay of MCI and MI in Shampoos Containing Plant Extracts.

A simple, easy-to-implement HPLC method was developed and validated for simultaneous determination of two isothiazolinone preservatives, methylchloroisothiazolinone (MCI) and methylisothiazolinone (MI), in hair care shampoo containing plant extracts. In this method, shampoo samples were first dissolved in isopropyl myristate and then MCI and MI were extracted from isopropyl myristate layer by a mixture of methanol and 0.02 M phosphate buffer solution pH 3.0 (30: 70, v/v) and analyzed on an analytical biphenyl column maintained at 25°C with a mixture of methanol and water (10: 90, v/v) in isocratic elution mode as mobile phase. Total flow rate of mobile phase was maintained at 1.0 mL per minute. The UV detection was performed at 274 nm. Injection volume was 50 μl. The method was fully validated in terms of specificity, linearity, precision, accuracy, and robustness according to requirements of AOAC International and was proved as reliable and suitable for the intended application.

Contact allergy to isothiazolinones epidemic: Current situation.

Since 2009, an increasing number of published cases of allergic contact dermatitis (ACD) from isothiazolinones in Europe was observed, amounting to an epidemic. However, only few studies have assessed the current situation after changes in European regulation. To analyze the incidence of isothiazolinone-related ACD in our area in the last decade. A retrospective study analyzed all patients patch tested in the allergy unit in a tertiary hospital in Spain between January 2010 and June 2019. Positive patch-test reactions to methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI) and/or MI alone were recorded. A total of 243 patients (9.55%) with positive patch-test reactions to MCI/MI and/or MI alone among 2544 consecutively patch-tested patients were recorded. An initial increase in the prevalence of MCI/MI allergy was observed, from 4.5% in 2010 reaching a peak in 2015, which was followed by a significant decrease until July 2019 with 3.1% prevalence in 2019. As shown in our data, regulatory interventions have resulted in a dramatic decrease in the prevalence of MCI and MI ACD, reaching a pre-epidemic level of 3.1% in 2019.

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

Methylisothiazolinone (MI) has caused an unprecedented epidemic of contact allergy in Europe and elsewhere. Subsequently, regulatory action has been taken, at least in Europe, aiming at reducing risk of MI sensitization. To follow-up on the prevalence of contact allergy to MI in consecutively patch tested patients and assess the spectrum of products containing MI or methylchloroisothiazolinone (MCI)/MI in patients positive to MI which elicited current allergic contact dermatitis. A cross-sectional survey was performed in 2016 and 2017, including all adult patients patch tested with the baseline series (including MI 0.2% aq.) between 1 May and 31 October at 14 centres in 11 European countries. Patients with positive reactions (+ to +++) to MI were further examined regarding history, clinical characteristics and eliciting products, which were categorized into 34 types and 4 classes (leave-on, rinse-off, household, occupational). The results were compared with the reference year 2015. A total of 317 patients, n=202 of 4278 tested in 2016 (4.72%) and n=115 of 3879 tested in 2017 (2.96%), had positive reactions to MI; the previous result from 2015 was 5.97% (P<0.0001). The share of currently relevant contact allergy among all positive reactions declined significantly as well (P=0.0032). Concerning product classes, a relative decline of leave-on and a relative increase of rinse-off and household products was noted. The prevalence of MI contact allergy decreased by 50% from 2015 to 2017. As a consequence of regulation, the share of cosmetics products (leave-on in particular) eliciting allergic contact dermatitis is decreasing. The chosen method of analysing causative products in sensitized patients has proven useful to monitor effects of intervention.

【論文摘要】The Association of Long-term PM2.5 Absorbance Exposure with Carotid-intima-media Thickness in Young Taiwanese

Background/Synopsis: The contribution of long-term air pollution exposures to subclinical atherosclerosis in young age has not been fully studied. Objectives/Purpose: This study is to evaluate to assess the associations of carotid intima-media thickness (CIMT) values in adolescents or young adults with one-year exposures to different sizes of particulate matter (PM) and traffic-related exhausts. Methods/Results: We recruited 789 school age subjects who resided in Taipei City and participated in the YOung TAiwanese (YOTA) Cohort between 1992 and 2000. Of all study subjects, 303 subjects were elevated blood pressures (EBP) and 486 subjects had normal BP (NBP) in the childhood. The CIMT values at different segments were measured at the age of 12-30 in the follow-up health examination from 2006 to 2008. Land-use regression models were used to estimate participants' one-year exposures to particulate matter (PM) of different sizes and traffic-related exhausts, including PM2.5 absorbance, nitrogen oxides, and nitrogen dioxides. Generalized linear regression was applied to assess the associations of CIMT values in adolescents or young adults with one-year exposures to six air pollutants. Our findings indicate one-year exposure to PM2.5 absorbance is associated with increased mean and maximum CIMT at different carotid segments. Specifically, exposure to PM2.5 absorbance among subjects who exhibited elevated childhood blood pressure is associated with an increases in mean CMIT at common carotid artery by 3.94% (95%CI: 0.24, 7.64), carotid bulb by 7.77% (95%CI: 2.95, 12.95), and internal carotid artery by 4.75% (95%CI: 0.67, 8.84). Similar increases in the maximum CIMT values were evident at the aforementioned sites. Moreover, older age, gender and health status (overweight, elevated blood pressure, hyperglycemia and hypercholesterolemia), coupled with high level exposure to PM2.5 absorbance (≥2.18 10-5 m-1; 75th percentile), are particularly at risk for developing increased CIMT. Conclusion: Long-term exposure to PM2.5 absorbance is positively associated with subclinical atherosclerosis in adolescents or young adults. The atherosclerosis developed since early childhood depending on individual cardiovascular risk factors including overweight, hypertension, hyperglycemia, or hypercholesterolemia, and can be modified by PM2.5 absorbance concentration.

Humidifier disinfectant and use characteristics associated with lung injury in Korea.

Since around the year 2000, hundreds of people in Korea have developed humidifier disinfectant-associated lung injury (HDLI). We collected all HD exposure-related information from the field investigations into the locations in which the 1199 registered patients had used HD. Among the people who registered, 38% (1st round=214, 2nd=73, 3rd=166) were confirmed as HDLI patients. Children aged under eight years old made up the highest proportion of HDLI cases (N=279, 62%), followed by pregnant women (N=31, 7%). One hundred thirty-three (29%) of the confirmed HDLI patients died. Fifty-seven percent of HDLI patients (N=259) developed HDLI after <1year of HD use. The number of HDLI patients who used only the Oxy Saksak HD brand was found to be 176 (39%), followed by the brands Cefu (N=27, 6%) and Aekyung (N=22, 5%). HD products containing only polyhexamethylene guanidine phosphate (PHMG-P) were the most frequently used among HDLI patients (N=234, 52%), followed by oligo (2-(2-ethoxy)ethoxyethyl) guanidinium (PGH) (N=27, 6%) and a mixture of chloromethylisothiazolinone (CMIT) and methylisothiazolinone (MIT) (N=26, 6%). The average PHMG-P inhalation level estimated from the patient group classified as suffering lung injury definitely associated with HD use was 145.1μg/m3 (N=91, SD=395.1μg/m3 ), higher than levels estimated from both the probable and possible HDLI patient groups. In conclusion, HD exposure-related variables, including type of HD brand and estimated inhalation HD level, were associated with the risk of HDLI.

Changing trends of contact allergens in Thailand: A 12‐year retrospective study

Contact allergen prevalences often change. Continual surveillance is necessary to detect trends in sensitization rates and emerging allergens. To identify the prevalence of, and trends in, the positive reactions to each allergen in the baseline series during a 12-year period in Thailand. The medical records of 2803 patients who underwent patch testing at the Contact Dermatitis Clinic, Siriraj Hospital, between 2006 and 2018, were retrospectively reviewed. The baseline series used by the clinic was adapted from the European and the International baseline series. The patch testing results were subdivided into 2-year blocks in order to compare the prevalences of each allergen. The prevalences of positive reactions to nickel, fragrance mixes I and II, dichromate, cobalt, carba mix, methyldibromo glutaronitrile, paraben mix, neomycin sulfate, methylisothiazolinone (MI), epoxy resin, N-isopropyl-N-phenyl-4-phenylenediamine and the corticosteroids significantly decreased. Methylchloroisothiazolinone (MCI)/MI was the only allergen associated with a significant increase of positive reactions, from 2.4% to 10.7%. However, the proportion of positive reactions to MCI/MI decreased in the final 2-year period. Approximately half of the substances in the screening patch test series showed a decline in the number of positive reactions, whereas MCI/MI showed an increasing prevalence.

Contact allergy to methylchloroisothiazolinone/methylisothiazolinone in north-eastern Italy: a temporal trend from 1996 to 2016.

Methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI) (Kathon® CG) is a common preservative used in industrial products, owing to its strong biocide effect. Contact allergy to MCI/MI has been reported in different occupations, including mechanics, hairdressers and healthcare workers. To retrospectively analyse the temporal trend of MCI/MI sensitization in north-eastern Italy and to evaluate the associations with occupations in our geographical area. From 1996 to 2016, 27381 patients with suspected allergic contact dermatitis were patch tested in eight departments of Dermatology or Occupational Medicine in north-eastern Italy. Individual characteristics were collected through a standardized questionnaire. The overall prevalence of MCI/MI sensitization was 4.2%, with the highest prevalence found in women and in patients younger than 25years. MCI/MI sensitization was significantly associated with atopic eczema (OR: 1.34, 95% CI: 1.10-1.70), hand/forearm dermatitis (OR: 1.20, 95% CI: 1.05-1.36) and face dermatitis (OR 1.30, 95% CI: 1.10-1.40). There was a significant association between MCI/MI sensitization and chemical processing workers (OR 1.74, 95% CI: 1.03-2.94), while mechanics and healthcare workers resulted more sensitized to this hapten only in the last 3years. Sensitization to MCI/MI is rising in the last years in Triveneto region, the 'epidemic' of sensitization to MCI/MI is mainly driven by extra-occupational dermatitis, and sensitization in some occupational groups is emerging only in the last years. A full labelling is compulsory for all products that contain isothiazolinones, to permit to identify the culprit agent.

Analysis of Preservative Capacity for Contemporary Iranian Shampoos

Preservative capacity is measured for seventeen currently accessible Iranian made shampoo products. Upon purchase, bacterial counts show no trace of any microbial contamination. The shampoo bottles are distributed to seventeen female graduate students, residing at the time in different dormitories of Tarbiat Modares University (TMU). After 40 days, the allocated bottles are returned and their bacterial counts repeated, under the same conditions. To our surprise, no trace of any microbial contamination is observed. Three possibilities are considered. 1) The factory employed preservative(s) act very efficiently. 2) The shampoo component(s) are themselves bactericidal. 3) Existence of sanitary conditions and the absence of any microbial contaminants at TMU! Evidently, the third possibility is ruled out. The second choice is also discarded, because practically no significant antimicrobial activity is demonstrated by any of the four main ingredients of the shampoos including sodium lauryl ether sulfate (SLES), betaine, coconut fatty acid, and glycerin. Hence, the most likely possibility is the first one, since upon deliberate contamination of the seventeen brands; the factory employed preservatives [5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one (KATHON CG)] prove highly bactericidal against four major contaminants: Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and the methicillin-resistant Staphylococcus aureus (MRSA).

Methylchloroisothiazolinone and/or methylisothiazolinone in cosmetic products-A market survey.

There was a global epidemic of methylchloroisothiazolinone (MCI) and/or methylisothiazolinone (MI) contact allergy from 2009 to 2015. In response, the Thai Ministry of Public Health regulated the use of MCI/MI in cosmetics. To survey the presence of MCI/MI and MI alone, as labelled on cosmetics sold on the Thai market, before and after the ministerial directive. The presence of MCI and/or MI in leave-on and rinse-off cosmetics sold on the market, based on the labelling of ingredients in 3445 products, was analysed. Before the implementation date, most leave-on products contained MCI/MI. After the regulations came into force, the only leave-on cosmetic subcategories that complied with the law were facial skin-care, sunscreen and make-up products. MCI/MI and MI alone were found on the labels of both leave-on and rinse-off products, the presence of each varying between product subcategories. Despite the ministerial regulations restricting their use, MCI and/or MI are still found in cosmetics sold on the Thai market. Dermatologists should be aware of this situation, and counsel patients to avoid products containing MCI and/or MI.

Risk Assessment of the Skin Sensitization Induction Potential of Kathon CG in Rinse-off and Leave-on Personal Care and Cosmetic Products.

Kathon CG is a commonly used cosmetic-grade preservative that contains active ingredients methylchloroisothiazolinone (MCI) and methylisothiazolinone (MI). The aim of the study was to perform a skin sensitization induction risk assessment of daily exposure to Kathon CG after use of various personal care and cosmetic products. We calculated an estimated daily consumer exposure level for rinse-off and leave-on products using the amount of product applied per application, number of applications per day, a retention factor, the MCI/MI concentration, and body surface area values. We assumed that the products contained the maximum recommended safe concentration of MCI/MI: 15 ppm in rinse-off products and 7.5 ppm in leave-on products. We compared estimated consumer exposure levels with the no expected sensitization induction level for MCI/MI and applied sensitization assessment factors to calculate product-specific margins of safety (MOSs). The MOSs for rinse-off products ranged from 5 to 63, whereas the MOSs for leave-on products ranged from 0.03 to 1.49. Overall, our results provide evidence that some leave-on products containing the maximum recommended safe concentration of Kathon CG may increase the risk of sensitization induction due to exposure to MCI/MI. In contrast, rinse-off products were not associated with a potential increased risk of skin sensitization induction.

Synthesis, Surface Activity, and Antimicrobial Efficacy of Diaryliodonium Salt‐Derived Amphiphiles

AbstractTwo sets of 19 amphiphiles derived from diaryliodonium salt in the form of 4‐methylbenzenesulfonate salts and trifluoromethanesulfonate salts were synthesized in good yields through the oxidation of 17 different aryl iodides using oxone (potassium peroxymonosulfate) as the oxidation agent in Route I and meta‐chloroperoxybenzoic acid as the oxidation agent in Routes II and III, followed by Friedel–Crafts reaction with (2‐(2‐(2‐methoxyethoxy)ethoxy)ethoxy)benzene to obtain the target compounds (1–19). Their structures were characterized by 1H nuclear magnetic resonance (NMR), 13C NMR, and high‐resolution mass spectrometry studies. Their surface activities were evaluated on the basis of surface tension and critical micelle concentration measurements by the Wilhelmy plate method at 25 °C. With their good water solubility, diaryliodonium salts (1–19) have excellent short‐term bactericidal efficacy against Bacillus cereus in the concentration of 600 ppm at 20 °C. After compounding 1 or 18 with the broad‐spectrum but skin‐irritating antibacterial agent Kathon CG (methylchloroisothiazolinone in combination with methylisothiazolinone) in the ratio of 1:1 by mass, both formulations maintained lethality rate of &gt;90% after 48 h.

The Role of Cleaning Products in Epidemic Allergic Contact Dermatitis to Methylchloroisothiazolinone/Methylisothiazolinone.

Sensitivity to methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI) has increased rapidly over recent years. This increase is mainly related to the extensive use of high concentrations of MI in cosmetic products, although a growing number of cases of occupational allergic contact dermatitis are caused by MCI/MI. The aim of this study was to examine the association between the increase in MCI/MI sensitization and the work performed by the patients in our area. A retrospective study was undertaken of the records of a total of 1179 patients who had undergone contact skin patch tests for MCI/MI from January 2005 to December 2015. A multivariate logistic regression analysis was performed to identify the factors independently associated with sensitivity to MCI/MI. A constant increase in MCI/MI sensitization was observed over the observation period. The only work associated with a significant increase in the prevalence of MCI/MI sensitization was cleaning, with 38.5% of the cleaning professionals with MCI/MI sensitization consulting for cosmetics-related dermatitis. Occupational sensitization to MCI/MI in cleaning professionals is worryingly increasing. This, in turn, could possibly account for many cases of cosmetics-associated contact dermatitis. Our findings suggest that a review of the regulations with regard to isothiazolinone concentrations in industrial and household detergents is necessary.

Isothiazolinones are still widely used in paints purchased in five European countries: a follow-up study.

An increasing incidence of contact allergy to methylisothiazolinone (MI) has been seen, caused, in particular, by cosmetic products and paints. A study from 2015 showed that 93.0% of paints bought in five European countries contained MI. New regulations have been discussed for paints in the EU, which may have influenced this market. To re-evaluate the use and concentrations of MI and four other isothiazolinones in water-based wall paints. Water-based white wall paints (n = 60) were purchased in retail stores in five European countries: Denmark, France, Germany, Sweden, and the United Kingdom. The paints were analysed for isothiazolione content by the use of high-performance liquid chromatography coupled to ultraviolet detection, and the results were confirmed with high-performance liquid chromatography-tandem mass spectrometry. MI was identified in 55 (91.7%) of the paints, with concentrations ranging from 1.1 to 142.7 ppm. The other isothiazolinones were identified in 20.0% [methylchloroisothiazolinone (MCI)] to 88.3% [benzisothiazolinone (BIT)] of the paints. BIT concentrations varied significantly between countries, whereas MI and MCI concentrations did not. There were no statistically significant differences in MI, MCI and BIT concentrations between the current study and the 2015 study. MI and other isothiazolinones are widely used in paints available in Europe. Their use does not seem to be decreasing.

Photoaggravated allergic contact dermatitis and transient photosensitivity caused by methylisothiazolinone.

Photoaggravated allergic contact dermatitis caused by methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI) and MI has been reported. To describe the clinical characteristics and results of (photo)patch tests and photo-tests of 10 patients in Belgium and France suffering from photoaggravated contact dermatitis caused by MI. Five men and five women, with a median age of 49.5 years, were investigated between January 2012 and February 2017 because of suspected photoaggravated contact dermatitis. Patch tests, photopatch tests and/or photo-tests were performed. Seven patients had positive patch test reactions to both MCI/MI and MI, whereas 3 patients had positive patch test reactions only to MI. In most cases, MI was the (strong) primary sensitizer. Photopatch tests with MCI/MI and/or MI gave stronger reactions than patch tests with these derivatives, indicating photoaggravation. Sensitization probably took place from cosmetics and work-related biocides, whereas elicitation of dermatitis was remarkably often related to airborne exposure to MI present in paints or industrial biocides. Four patients suffered from transient photosensitivity. Photoaggravated allergic contact dermatitis and transient photosensitivity caused by MI is a peculiar clinical presentation of allergic contact dermatitis caused by this preservative, and should be considered in daily clinical practice.