Isothiazolinone derivatives and allergic contact dermatitis: a review and update

Contact sensitization and self-reported eczema in Swedish painters with occupational exposure to isothiazolinones

BACKGROUND

Due to an increasing occupational usage of isothiazolinone (IT)-containing preservatives, and their potential to cause skin sensitization and allergic contact dermatitis, that is, chronic disease, there is a need for more knowledge on how highly exposed workers are affected.

OBJECTIVES

The overall objective was to explore dermatological symptoms of potentially long-lasting or chronic character in Swedish painters.

METHODS

Building painters from western and southern Sweden were initially invited to perform a questionnaire on occurrence of skin symptoms. Participants with affirmative responses, and the right inclusion criteria, were further invited to patch testing with four different ITs: benzisothiazolinone (BIT), methylisothiazolinone, methylchloroisothiazolinone and octylisothiazolinone.

RESULTS

There was a tendency towards higher occurrence of positive patch test reactions among the painters compared with occupationally unexposed registry patients; however, not statistically significant differences. BIT was the substance most frequently causing positive test results in both groups. The occurrence of adult-onset eczema was higher in painters than in the control group of electricians, and just shy of statistical significance concerning any of several skin locations (face/legs/arms/hands).

CONCLUSION

Building painters present with positive patch test reactions to common paint preservatives (ITs), and they report adult-onset eczema more often than do less occupationally exposed groups.

Lessons learned in a decade: Medical-toxicological view of tattooing

Tattooing has been part of the human culture for thousands of years, yet only in the past decades has it entered the mainstream of the society. With the rise in popularity, tattoos also gained attention among researchers, with the aim to better understand the health risks posed by their application. 'A medical-toxicological view of tattooing'-a work published in The Lancet almost a decade ago, resulted from the international collaboration of various experts in the field. Since then, much understanding has been achieved regarding adverse effects, treatment of complications, as well as their regulation for improving public health. Yet major knowledge gaps remain. This review article results from the Second International Conference on Tattoo Safety hosted by the German Federal Institute for Risk Assessment (BfR) and provides a glimpse from the medical-toxicological perspective, regulatory strategies and advances in the analysis of tattoo inks.

Increasing non-cosmetic exposure and sensitization to isothiazolinones require action for prevention: Review

Frequent use of methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) and MI in cosmetic products has been the main cause of widespread sensitization and allergic contact dermatitis to these preservatives (biocides). Their use in non-cosmetic products is also an important source of sensitization. Less is known about sensitization rates and use of benzisothiazolinone (BIT), octylisothiazolinone (OIT), and dichlorooctylisothiazolinone (DCOIT), which have never been permitted in cosmetic products in Europe. BIT and OIT have occasionally been routinely patch-tested. These preservatives are often used together in chemical products and articles. In this study, we review the occurrence of contact allergy to MI, BIT, OIT, and DCOIT over time, based on concomitant patch testing in large studies, and case reports. We review EU legislations, and we discuss the role of industry, regulators, and dermatology in prevention of sensitization and protection of health. The frequency of contact allergy to MI, BIT, and OIT has increased. The frequency of contact allergy to DCOIT is not known because it has seldom been patch-tested. Label information on isothiazolinones in chemical products and articles, irrespective of concentration, is required for assessment of relevance, information to patients, and avoidance of exposure and allergic contact dermatitis.

Antimicrobial, Preservative, and Hazard Assessments from Eight Chemical Classes

Preservatives, such as isothiazolinones and formaldehyde-releasing compounds, provide safety and stability in consumer products by preventing microbial contamination. Yet these ingredients present human and environmental hazards, including allergic contact dermatitis and aquatic toxicity. The development of safer alternatives has been stymied by trade-offs between safety and efficacy. To enable the identification of safer preservatives, substances from eight functional classes were assessed for antimicrobial efficacy and human and environmental hazards. First, 130 substances were evaluated for microbial inhibitory activity against two relevant model microorganisms, Aspergillus brasiliensis (filamentous fungi) and Pseudomonas aeruginosa (Gram-negative bacteria). High-performing compounds within each class were assessed for hazards across a broad suite of human and environmental health end points. Four promising compounds were selected for further testing based on microbial inhibition, hazard profiles, and commercial availability. These ingredients were tested for biocidal activity in model home care formulations using methods adapted from industrial preservative challenge guidelines (USP-51). Two substances were identified, caprylhydroxamic acid and caprylyl glycol, that provided adequate preservation and improved toxicity profiles compared to isothiazolinone and formaldehyde-releasing preservatives. This study highlights trade-offs between antimicrobial activity and hazards across a broad spectrum of chemical classes relevant to safer preservative development.

The new Italian SIDAPA Baseline Series for patch testing (2023): an update according to the new regulatory pathway for contact allergens

Allergic contact dermatitis (ACD) is a common inflammatory skin disease caused by delayed hypersensitivity to chemical and biotic contact allergens. ACD significantly affects the patients' quality of life negatively impacting both occupational and non-occupational settings. Patch testing is the gold standard diagnostic in vivo test to precise the ACD etiology and to correctly perform prevention. According to the Italian Medicines Agency (AIFA) legislative decree no. 178 of 29th May 1991, allergens are defined as medicines and therefore they are subject to strict regulation. In 2017, AIFA (decree no. 2130/2017) started a procedure to regulate contact allergens on the Italian market and actually the contact allergens temporarily authorized are reported in AIFA decree no. 98/2022, valid until November 2023. The availability on the market of contact allergens to diagnose ACD and continuous updating on the basis of new epidemiological trends are mandatory, jointly with the continuous update of the baseline and integrative series for patch testing. For this reason, the scientific community represented in Italy by the Skin Allergies Study Group of SIDeMaST (Italian Society of Dermatology and Venereology) and SIDAPA (Italian Society of Allergological, Occupational and Environmental Dermatology) are constantly working, in close relationship with the European scientific communities with large expertise in this important sector of the modern Dermatology. Herein, we report the setting up of regulatory legislation by AIFA and the new Italian Adult Baseline Series for patch testing.

Polysensitization in the Spanish Contact Dermatitis Registry (REIDAC): A 2019-2022 prospective study with cluster and network analysis

BACKGROUND

There is still limited clinical-practice data on specific clinical and patch test features, as well as on allergen clusters in polysensitization (PS).

OBJECTIVES

To determine the frequency, relevance, symptoms duration and risk factors in polysensitized patients and to assess possible allergen aggregation.

METHODS

Prospective multicentric study (January 2019-December 2022) conducted in setting of the Spanish Contact Dermatitis Register (REIDAC). Clinical and patch test data of polysensitized and oligosensitized patients were compared, and risk factors of PS were investigated with logistic multivariate regression. Unsupervised hierarchical clustering and network analysis were used to study allergen aggregation in PS.

RESULTS

A total of 10,176 patients were analysed. PS was found in 844 (8.3%). Current relevance was significantly higher in polysensitized patients (p < 0.01). Risk factors for PS were atopic dermatitis (OR: 1.58, 95% CI: 1.24-2.02), age (≥60 years vs. ≤24 years, OR: 1.75, 95% CI: 1.25-2.44) and some special locations (legs vs. face OR: 1.54, 95% CI: 1.05-2.25, hands vs. face OR: 1.46, 95% CI:1.15-1.85, arms vs. face OR: 1.49, 95% CI:1.01-2.20, trunk vs. face OR: 1.40, 95% CI:1.06-1.85). Cluster and network analyses revealed specific-allergen clusters and significant associations, including allergens belonging to metals group, fragrances and botanicals group, topical drugs group, rubber allergens and biocides.

CONCLUSIONS

This study confirms that PS is structured by discernible patterns of specific-allergen clusters and reinforces significant allergen associations in PS. Cross-reactivity and/or concomitant sensitization could explain the formation of allergen clusters in PS.

Allergic contact dermatitis to footwear in Thailand: Prevalence, clinical characteristics and common allergens

BACKGROUND

Footwear contact allergy is caused by exposure to allergens in shoes. The prevalence and common allergens vary by region and time due to differences in customs and lifestyle.

OBJECTIVES

To determine the clinical characteristics and common allergens of patients with footwear-related allergic contact dermatitis (ACD) who attended Siriraj Hospital in Bangkok, Thailand, between 2001 and 2020.

METHODS

The medical records of 247 patients with clinically suspected footwear dermatitis who underwent patch testing were reviewed.

RESULTS

The prevalence of ACD to footwear was 1.8%. Females were predominant (71.6%). The three most common allergens were carba mix (7.7%), mercapto mix (6.9%) and potassium dichromate (6.9%). According to the allergens found, rubber (14.2%), adhesives (7.7%) and leathers (6.9%) were the three most common groups. Dorsal-limited skin lesions were significantly associated with footwear ACD.

CONCLUSION

Rubber and leather allergens were still the most common culprit allergens. Dermatologists should keep up-to-date on common allergens in footwear and emerging allergens to include in patch test series.

Potency classification of isothiazolinone compounds based on defined approaches of skin sensitization in OECD GL 497

Regulatory decisions for skin sensitization are now based on adverse outcome pathway (AOP) and integrated approaches to testing and assessment (IATA). Based on these, Organisation for Economic Co-operation and Development (OECD) guidelines on defined approaches for skin sensitization were adopted with a fixed data interpretation procedure (DIP). In the guidelines, "Defined Approaches" (DA) on skin sensitization uses the results from multiple information sources of in chemico, in vitro, and in silico data to achieve an equivalent predictive capacity as those of the animal tests. In this review, we evaluated the skin sensitization of eleven isothiazolinone compounds including 4,5-Dichloro-2-octyl-3(2H)-isothiazolone (DCOIT), 2-n-Octyl-4-isothiazolin-3-one (OIT), 2-Methyl-4-isothiazolin-3-one (MIT), 1,2-Benzisothiazolin-3-one (BIT), 1,2-Benzisothiazolin-3-one, 2-butyl (BBIT), 5-Chloro-2-methyl-4-isothiazolin-3-one (CMIT), 2-methyl-4,5-trimethylene-4-isothiazolin-3-one (MTMIT), 2-methyl-1,2-benzothiazol-3-one (MBIT), 2-methyl-1,2-benzothiazole-3-thione (MBIT-S), 1,2-benzisothiazolin-3-one, 2-methyl-, 1,1-dioxide (BBIT-O), and a mixture of CMIT/MIT. Data from direct peptide reactivity assay (DPRA), human cell line activation (h-CLAT) test, and quantitative structure activity relationship (QSAR) Toolbox were evaluated and were applied to the DIP to derive a prediction of hazard identification and a potency classification. Among the evaluated chemicals, six isothiazolinone compounds were classified to be UN GHS 1A, one compound to be UN GHS 1, and four compounds could not be classified due to lack of data. The results of sensitizer chemicals were found to coincide well with those of in vivo test.

Isothiazolinone dysregulates the pattern of miRNA secretion: Endocrine implications for neurogenesis

Isothiazolinones are extensively used as preservatives and disinfectants in personal care products and household items. The unintended exposure of humans and animals to isothiazolinones has led to increasing concerns about their health hazards. The compound 4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT), a representative isothiazolinone, can simultaneously induce endocrine disruption and neurotoxicity. However, the underlying mechanisms and linkages remain unclear. Our purpose was to elucidate the role of miRNAs as the signaling communicator during the crosstalk between endocrine and nervous systems in response to DCOIT stress. H295R cells were exposed to DCOIT, after which the alterations in intracellular miRNA composition, exosome secretory machinery, and extracellular miRNA composition were examined. Then, a PC12 cell line of neuronal differentiation potential was cultured with the extract of extracellular miRNAs from DCOIT-exposed H295R cell media to explore the functional implications in neurogenesis. The results showed that DCOIT exposure resulted in 349 differentially expressed miRNAs (DEMs) in H295R cells, which were closely related to the regulation of multiple endocrine pathways. In the media of H295R cells exposed to DCOIT, 66 DEMs were identified, showing distinct compositions compared to intracellular DEMs with only 2 common DEMs (e.g., novel-m0541-5p of inverse changes in the cell and medium). Functional annotation showed that extracellular DEMs were not only associated with sex endocrine synchronization, but were also implicated in nervous system development, morphogenesis, and tumor. Incubating PC12 cells with the extracellular exosomes (containing miRNAs) from DCOIT-exposed H295R cells significantly increased the neurite growth, promoted neuronal differentiation, and shaped the transcriptomic fingerprint, implying that miRNAs may communicate transduction of toxic information of DCOIT in endocrine system to neurons. Overall, the present findings provide novel insight into the endocrine disrupting and neural toxicity of DCOIT. The miRNAs have the potential to serve as the epigenetic mechanism of systems toxicology.

Analysis of Adverse Reactions of Cosmetics in Chinese Han Population in Recent Five Years

Background

There are still some gaps in the summary and generalization of cosmetic-related adverse reaction reports.

Objective

The aim of this study is to summarize and analyze the occurrence of cosmetic adverse reactions in Shanghai Han population by using available survey data.

Materials and Methods

Collection, statistics and analysis of patients with cosmetic adverse reactions in Shanghai Huashan Hospital from 2017 to 2021.

Results

Among the 1004 patients, most of them (96.71%) were diagnosed as cosmetic contact dermatitis, which often occurred within 3 days of using cosmetics (51.79%). A total of 260 patients were tested with patch test, but the compliance rate was only 18.08%. Among them, 240 patients underwent additional European standard allergen tests, and positive allergens were detected in 210 cases (87.5%). Univariate analysis revealed that dosage form (emulsion and cream), age (≤25 years) and the allergic ingredients triethanolamine, rose oil, propylene glycol, thiomersal and musk ambrette are associated with the occurrence of cosmetic adverse reactions within seven days. A logit prediction model was also successfully constructed: Logit (P) = 1.710-0.796×1 + 1.185×2 -3.650X3-1.335X4.

Conclusion

This study complements the data reported on cosmetic adverse reactions in the Chinese Han population and suggests that in future clinical diagnosis and data collection, emphasis should be placed on patch testing, combining the patch test with cosmetic protoplast with the European standard allergen test to improve the detection rate.

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.

Assessing the risk of induction of skin sensitization to plant protection products: A quantitative approach

Exposure to skin sensitizers is common and regulated in many industry sectors. For cosmetics, a risk-based approach has been implemented, focused on preventing the induction of sensitization. First, a No Expected Sensitization Induction Level (NESIL) is derived, then modified by Sensitization Assessment Factors (SAFs) to derive an Acceptable Exposure Level (AEL). The AEL is used in risk assessment, being compared with an estimated exposure dose, specific to the exposure scenario. Since in Europe there is increased concern regarding exposure towards potentially sensitizing pesticides via spray drift, we explore how existing practice can be modified to allow Quantitative Risk Assessment (QRA) of pesticides for bystanders and residents. NESIL derivation by the Local Lymph Node Assay (LLNA), the globally required in vivo assay for this endpoint, is reviewed alongside consideration of appropriate SAFs. Using a case study, the principle that the NESIL in μg/cm² can be derived by multiplying LLNA EC3% figure by a factor of 250 is adopted. The NESIL is then reduced by an overall SAF of 25 to establish an exposure level below which there is minimal bystander and resident risk. Whilst this paper focuses on European risk assessment and management, the approach is generic and universally applicable.

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.

Toxicological signature for thyroid endocrine disruption of dichlorooctylisothiazolinone in zebrafish larvae

Dichlorooctylisothiazolinone (DCOIT), which is one of the isothiazolinone preservatives, is applied to water-based adhesives in food packaging. This study investigated the effects of DCOIT on the embryonic growth and thyroid endocrine system using zebrafish. Organism-level (hatchability, survival, and growth), hormone-level (triiodothyronine (T3) and thyroxine (T4)), gene-level (genes associated with the hypothalamus-pituitary-thyroid axis), and microRNA-level (microRNAs related to thyroid endocrine disruption) endpoints were measured. Significant rise in embryonic coagulation and delayed hatching (≥0.3 μg/L), and decreased larval length (30 μg/L) were observed in fish exposed to DCOIT. Lower contents of T3 and T4 were observed after exposure to DCOIT, which was accompanied by the upregulation of genes associated with the thyrotropin releasing hormone and thyroid stimulating hormone and the downregulation of genes associated with the thyroid hormone receptors and deiodination. Strong influence of DCOIT on dre-miR-193b and -499 may be a critical mechanism to inhibit transcription of trαa and trβ, which in turn may affect thyroid hormones and development of the organism. Our findings suggest that hypothyroidism induced by the exposure to DCOIT is potentially associated with genetic and microRNA-level changes, which eventually affects development.

Disposition of Aerosols of Isothiazolinone-Biocides: BIT, MIT and OIT

Biocides are widely used in everyday life, and accordingly, human exposure to them is inevitable. Especially, the inhalational exposure of humans to biocides and resultant respiratory toxicity are gaining public interest due to the recent catastrophe associated with humidifier disinfectants. Aerosolized chemicals are subject to gravitational deposition and chemical degradation. Therefore, the characterization of the disposition of aerosols is essential to estimate the inhalational exposure to biocides. Here, we compared the disposition of aerosols of one of the commonly used biocide classes, isothiazolinone-based biocides, BIT, MIT, and OIT. An acrylic chamber (40 cm × 40 cm × 50 cm) was created to simulate the indoor environment, and a vacuum pump was used to create airflow (1 LPM). Biocides were sprayed from a vertical nebulizer placed on the ceiling of the chamber, and the distribution of particle sizes and volume was measured using the Optical Particle Sizer (OPS) 3330 device. During and after the aerosol spraying, airborne biocides and those deposited on the surface of the chamber were sampled to measure the deposition using LC-MS/MS. As a result, the broad particle size distribution was observed ranging from 0.3 to 8 μm during the nebulization. The inhalable particle faction (>2 μm) of the isothiazolinones was 32−67.9% in number but 1.2 to 6.4% in volume. Most of the aerosolized biocides were deposited on the chamber’s surface while only a minimal portion was airborne (<1%) after the nebulization. More importantly, significant amounts of MIT and OIT were degraded during aerosolization, resulting in poor total recovery compared to BIT (31%, 71% vs. 97% BIT). This result suggests that some isothiazolinones may become unstable during nebulization, affecting their disposition and human exposure significantly.

Preservatives in non-cosmetic products: Increasing human exposure requires action for protection of health

The widespread use of skin sensitizing preservatives is well-known. Contact allergy to preservatives is often caused by their presence in cosmetic products. Preservative use in non-cosmetic products is less well-known. We have reviewed European Union (EU) legislations on classification and labelling, biocides and cosmetics, concerning conditions for use of the most used sensitizing preservatives (including formaldehyde-releasing substances, isothiazolinones and parabens). We have analysed temporal trends in their use in non-cosmetic products (tonnes, number of products, concentrations), based on annual reports to the Swedish Products Register 1995-2018; and we discuss implications for stakeholders. Major changes over time are that the use of most of the preservatives has increased by tonnes and/or by number of products, and that several use concentrations have declined following harmonized classification as a skin sensitizer with low concentration limits for this classification. We conclude that the massive increase in use of preservatives is alarming, and that urgent action is needed for protection of health. Their use in non-cosmetic products is broad, increasing and often undisclosed. In the EU, legislations concerning chemicals can provide relevant restrictions to reduce their use and associated health risks, monitored by efficient surveillance. Prevention would be benefited by better coordination between legislations.

A Multidisciplinary Approach in Examining the Susceptibility to Microbial Attack of Polyacrylic and Polyurethane Resins Used in Art Restoration

The synthetic polymers used to protect artworks from deterioration process can be colonized by the fungi and bacteria responsible for the biodeterioration process. In this study, the susceptibility of synthetic polyacrylics and polyurethane resins to microorganisms (Aspergillus niger ATCC 9642, Aureobasidium pullulans ATCC 15233, Chaetomium globosum ATCC 6205, Cladosporium cladosporioides ATCC 16022, Alternaria alternata BC01, Penicillium citrinum LS1 and Pseudomonas aeruginosa ATCC 9027) was investigated. The microbial attack was simulated alone and with a biocide and the related growth was observed up to 21 days for bacteria and 28 days for fungi. The polyacrylic and polyurethane resins were subjected to microbial attack, regardless of the biocide treatment, with a fungal growth from 60% to the complete coverage of the plate surface. Penicillium citrinum showed the greatest adaptation ability and was found in all the examined resins. P. aeruginosa was visible in all the different resins, regardless of the presence of biocide. An environmental scanning electron microscope (ESEM) revealed the presence of fungal conidia and hyphae in the inoculated resins and the Fourier transform IR spectroscopy (FTIR-ATR) indicated chemical transformations in the IR spectra, particularly the hydrolysis of esters, with some differences between the polyacrylic and polyurethane resins, which were probably due to their different chemical features. Overall, our data stress that the chemical, physical and biological deterioration caused by microorganisms capable of degrading synthetic polymers is still a problem in art restoration and that new strategies must be considered to counteract this phenomenon.

Functional and dynamic mitochondrial damage by chloromethylisothiazolinone/methylisothiazolinone (CMIT/MIT) mixture in brain endothelial cell lines and rat cerebrovascular endothelium

The mixture of 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT, chloromethylisothiazolinone) and 2-methyl-4-isothiazolin-3-one (MIT, methylisothiazolinone) is a commonly used biocide in consumer products. Despite the health issues related to its usage in cosmetics and humidifier disinfectants (HD), understanding its adverse outcome is still limited. Using in vitro cell lines and ex vivo rat models, we examined the effects of CMIT/MIT on the cellular redox homeostasis and energy metabolism in the brain microvascular endothelium, a highly restrictive interface between the bloodstream and brain. In murine bEND.3 and human hCMEC/D3, CMIT/MIT significantly amplified the mitochondrial-derived oxidative stress causing disruption of the mitochondrial membrane potential and oxidative phosphorylation at a sub-lethal concentration (1 μg/mL) or treatment duration (1 h). In addition, CMIT/MIT significantly increased a dynamic imbalance between mitochondrial fission and fusion, and endogenous pathological stressors significantly potentiated the CMIT/MIT-induced endothelial dysfunction. Notably, in the brain endothelium isolated from intravenously CMIT/MIT-administered rats, we observed significant mitochondrial damage and decreased tight junction protein. Taken together, we report that CMIT/MIT significantly impaired mitochondrial function and dynamics resulting in endothelial barrier dysfunction, giving an insight into the role of mitochondrial damage in CMIT/MIT-associated systemic health effects.

Genetic validation of Aspergillus fumigatus phosphoglucomutase as a viable therapeutic target in invasive aspergillosis

Aspergillus fumigatus is the causative agent of invasive aspergillosis, an infection with mortality rates of up to 50%. The glucan-rich cell wall of A. fumigatus is a protective structure that is absent from human cells and is a potential target for antifungal treatments. Glucan is synthesized from the donor uridine diphosphate glucose, with the conversion of glucose-6-phosphate to glucose-1-phosphate by the enzyme phosphoglucomutase (PGM) representing a key step in its biosynthesis. Here, we explore the possibility of selectively targeting A. fumigatus PGM (AfPGM) as an antifungal treatment strategy. Using a promoter replacement strategy, we constructed a conditional pgm mutant and revealed that pgm is required for A. fumigatus growth and cell wall integrity. In addition, using a fragment screen, we identified the thiol-reactive compound isothiazolone fragment of PGM as targeting a cysteine residue not conserved in the human ortholog. Furthermore, through scaffold exploration, we synthesized a para-aryl derivative (ISFP10) and demonstrated that it inhibits AfPGM with an IC50 of 2 μM and exhibits 50-fold selectivity over the human enzyme. Taken together, our data provide genetic validation of PGM as a therapeutic target and suggest new avenues for inhibiting AfPGM using covalent inhibitors that could serve as tools for chemical validation.

Effects of Fisetin on Allergic Contact Dermatitis via Regulating the Balance of Th17/Treg in Mice

Background. Allergic contact dermatitis (ACD) is a form of chronic cutaneous inflammatory disease of immunological origin that has adverse impacts on patient quality of life, underscoring the need for the development of safe and effective therapeutic agents to treat affected individuals. Fisetin is a Chinese herbal preparation that reportedly exhibits antitumor, antioxidant, antimicrobial, anticoagulatory, and antimalarial activity. In the current report, the immunomodulatory activity of fisetin was appraised by assessing its impact on balance between regulatory T (Treg) and Th17 cells in an ACD model. Methods. BALB/c mice ( $n=60$ ) were randomized into control, ACD model, CTX positive control (20 mg/kg), and fisetin treatment groups (three dose levels: 2, 4, or 8 mg/kg). ACD induction was achieved by sensitizing mice on the shaved ventral abdomen via the application of 5% DNFB (50 μL) on days 1 and 2, followed by rechallenge in the right ear with 5% DNFB (20 μL) on day 5. Beginning on day 1, immunized mice were intraperitoneally injected with the appropriate fisetin dose (in saline) once per day for 7 days. On day 7, ear swelling, transcription factor expression, Th17/Treg cell populations, and cytokine production were assessed in vivo. Results. Fisetin treatment significantly suppressed ear swelling and associated inflammatory cell infiltration, besides reducing the production of Th17 cytokines (IL-17, TNF-α, and IL-6) and the expression of the Th17 lineage transcription factor RORγt while simultaneously enhancing Treg-specific cytokine production (TGF-β and IL-10) and the expression of the Treg lineage transcription factor Foxp3, thereby restoring the Th17/Treg cell in ACD mice. Conclusions. These data indicate that fisetin exhibits immunomodulatory activity and can alter the Th17/Treg cell balance, highlighting its potential value as a treatment drug for ACD.

Effect of Cosmetics Use on the In Vitro Skin Absorption of a Biocide, 1,2-Benzisothiazolin-3-one

1,2-Benzisothiazolin-3-one (BIT) is a commonly used organic biocide containing an isothiazolone ring. However, it may have adverse effects on human health and its risk needs to be properly evaluated. Dermal exposure is the main route of BIT exposure, and co-exposed substances may affect its absorption. The dermal permeation profile of BIT has not been well-studied. This study aimed to investigate the dermal permeation profiles of BIT with or without cosmetic use. Dermal permeation profiles of BIT were investigated after infinite- (100 μg/cm²), or a finite-dose (10 μg/cm²) application with or without cosmetics using a minipig skin and Strat-M^®, an artificial membrane. A cream, lotion, and essence (namely, face serum) were pre-treated as representative cosmetics on minipig skin for 30 min, with BIT treatment afterward. After the treatment, BIT left on the skin surface was collected by cotton swabbing, BIT in the stratum corneum, by sequential tape stripping, and BIT retained in the remaining skin was extracted after cutting the skin into pieces before LC-MS/MS analysis. When an infinite dose was applied, permeation coefficients (K_p, cm/h) for minipig skin and Strat-M^® were 2.63 × 10⁻³ and 19.94 × 10⁻³, respectively, reflecting that skin permeation was seven to eight times higher in Strat-M^® than in the minipig skin. BIT, in the presence of cosmetics, rapidly permeated the skin, while the amount in the stratum corneum and skin deposit was reduced. We performed a risk assessment of dermally applied BIT in the absence or presence of cosmetics by calculating the skin absorption rate at 10 h based on the toxicological data from several references. The risk level was higher in the presence of essence as compared to lotion, which was higher than cream, which was higher than the control (non-treated). However, all of the margins of safety values obtained were greater than 100, suggesting that BIT is safe for use in dermally exposed consumer products. We believe that this research contributes to a greater understanding of the risk assessment of isothiazolinone biocides.

Cosmetic preservative labelling in philippine products in accordance with philippine regulations

BACKGROUND

Preservatives are usually added to a wide array of consumer products to prevent growth of microbes and to prevent product destabilization and degradation. However, many of these preservatives are common skin sensitizers and may cause allergic contact dermatitis. The amount of preservatives may vary per country or region according to their respective legislation, and may be reported in differences in prevalence rates of contact dermatitis.

OBJECTIVE

To examine and identify preservatives in consumer products in accordance with Philippine legislation. To verify the accuracy of the list of ingredients of Philippine cosmetic products as legislated by the Philippine Bureau of Food and Drug Administration.

METHODS

A total of 65 commonly used Philippine consumer products ranging from liquid facial and body washes, bar soaps, laundry detergents, feminine hygiene washes and wipes, shampoos and conditioners, sunblock, and moisturizers were selected. Ingredients noted on labels were documented. Products were subsequently investigated chemically for the presence of either methylchloroisothiazolinone, methylisothiazolinone, and formaldehyde.

RESULTS

The preservatives most commonly used in cosmetic products in the Philippine market are: methylchloroisothiazolinone (MCI), methylisothiazolinone (MI), and/or formaldehyde. In accordance with Philippine legislation, almost all products provided a detailed ingredient list as printed on the packaging. Measurements of MCI/MI ranged from less than 1 ppm to 16 ppm, and MI only ranged from less than 1 ppm to 66 ppm, whereas formaldehyde was noted to range from less than 2.5 ppm to greater than 40 ppm in the products tested. Most products are manufactured by international brands with a few products being manufactured locally.

CONCLUSIONS

The preservatives found in cosmetic products were MCI, MI and formaldehyde. There were discrepancies found in the preservatives and labelling of these products, with a majority of investigated Philippine products labelled inaccurately with varying concentrations of preservatives. This article is protected by copyright. All rights reserved.

3D Printed SERS-Active Thin-Film Substrates Used to Quantify Levels of the Genotoxic Isothiazolinone

Several reports present methods to fabricate thin-film substrates capable of surface-enhanced Raman scattering (SERS). Substrates synthesized by displacing silver onto copper using facile synthesis methods such as galvanic displacement can generate high levels of SERS enhancement rivaling commercially available substrates manufactured by lithographic methods. Here, we describe the optimization of a novel set of SERS-active thin-film substrates synthesized via the electroless displacement of Ag onto the surface of three-dimensional (3D) printed disks composed of the copper/polymer (PLA) composite filament. The effect of AgNO₃ concentration on the deposition, morphology, and overall SERS activity of the substrates has been carefully studied. Two commonly used Raman reporters, 4-mercaptobenzoic acid (MBA) and malachite green isothiocyanate (MGITC), were used to measure the SERS output of the substrates. Good SERS signal reproducibility (RSD ∼16.8%) was measured across the surface of replicate substrates and high-sensitivity detection of MBA was achieved (10^-12 M). To test the real-world application of our substrates, we opted to detect 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT), which is a genotoxic, biocide common in many household products, known to leach into water supplies. Our newly developed SERS-active substrates could detect CMIT down to 10 ppm when spiked in simulated lake water samples, which is well within current agency standards.

Current and future chemical treatments to fight biodeterioration of outdoor building materials and associated biofilms: Moving away from ecotoxic and towards efficient, sustainable solutions

All types of building materials are rapidly colonized by microorganisms, initially through an invisible and then later a visible biofilm that leads to their biodeterioration. Over centuries, this natural phenomenon has been managed using mechanical procedures, oils, or even wax. In modern history, many treatments such as high-pressure cleaners, biocides (mainly isothiazolinones and quaternary ammonium compounds) are commercially available, as well as preventive ones, such as the use of water-repellent coatings in the fabrication process. While all these cleaning techniques offer excellent cost-benefit ratios, their limitations are numerous. Indeed, building materials are often quickly recolonized after application, and microorganisms are increasingly reported as resistant to chemical treatments. Furthermore, many antifouling compounds are ecotoxic, harmful to human health and the environment, and new regulations tend to limit their use and constrain their commercialization. The current state-of-the-art highlights an urgent need to develop innovative antifouling strategies and the widespread use of safe and eco-friendly solutions to biodeterioration. Interestingly, innovative approaches and compounds have recently been identified, including the use of photocatalysts or natural compounds such as essential oils or quorum sensing inhibitors. Most of these solutions developed in laboratory settings appear very promising, although their efficiency and ecotoxicological features remain to be further tested before being widely marketed. This review highlights the complexity of choosing the adequate antifouling compounds when fighting biodeterioration and proposes developing case-to-case innovative strategies to raise this challenge, relying on integrative and multidisciplinary approaches.

Demographic and clinical profile of occupational cases of sensitization to methylisothiazolinone and Kathon CG: a cross-sectional study

Abstract Introduction: methylisothiazolinone alone or associated with methylchloroisothiazolinone (Kathon CG) is a preservative related to occupational allergic contact dermatitis. Objectives: to evaluate the demographic and clinical profile of occupational cases of sensitization to isothiazolinones in the city of Rio de Janeiro and to describe the presence of these preservatives in national paints. Methods: cross-sectional study based on information from medical records of workers who underwent patch testing between 2013-2017. The prevalence of clinical, demographic and occupational characteristics was described and an unadjusted model was used to investigate the association between variables. We sought the presence and concentration of isothiazolinones in the chemical composition sheets of national paints. Results: among the 768 workers submitted to the tests, 68 had occupational dermatosis with a positive result for sensitization to methylisothiazolinone/Kathon CG. The most affected occupations were those related to domestic activities and cleaning. There was a greater likelihood of sensitization to isothiazolinones in women and in those with involvement of the hands and legs. Among the 61 paints evaluated, 26 had some isothiazolinone, with methylchloroisothiazolinone being the most common. Conclusions: sensitization to isothiazolinones can impact workers’ health and demands greater vigilance on cleaning materials and cosmetics, as well as discussing the composition regulation of the paints sold in Brazil.

Perfil demográfico e clínico de casos ocupacionais de sensibilização a metilisotiazolinona e Kathon CG: estudo seccional

Resumo Introdução: a metilisotiazolinona isolada ou associada à metilcloroisotiazolinona (Kathon CG) é um conservante relacionado à dermatite de contato alérgica ocupacional. Objetivos: avaliar o perfil demográfico e clínico dos casos ocupacionais de sensibilização a isotiazolinonas no município do Rio de Janeiro e descrever a presença desses preservativos em tintas nacionais. Métodos: estudo transversal baseado em informações de prontuários de trabalhadores submetidos a testes de contato entre 2013-2017. Descreveu-se a prevalência de características clínicas, demográficas e ocupacionais e utilizou-se um modelo não-ajustado para investigar a associação entre variáveis. Buscou-se a presença e a concentração de isotiazolinonas nas fichas de composição química de tintas nacionais. Resultados: dentre os 768 trabalhadores submetidos aos testes, 68 apresentavam dermatose ocupacional com resultado positivo para sensibilização à metilisotiazolinona/Kathon CG. As profissões mais acometidas foram as relacionadas a atividades domésticas e limpeza. Houve maior chance de sensibilização às isotiazolinonas nas mulheres e naqueles com acometimento das mãos e das pernas. Entre as 61 tintas avaliadas, 26 possuíam alguma isotiazolinona, sendo a metilcloroisotiazolinona a mais comum. Conclusões: a sensibilização às isotiazolinonas pode impactar a saúde do trabalhador e demanda maior vigilância com materiais de limpeza e cosméticos, assim como a discussão da regulação da composição de tintas comercializadas no país.

Comparative study of two isothiazolinone biocides, 1,2-benzisothiazolin-3-one (BIT) and 4,5-dichloro-2-n-octyl-isothiazolin-3-one (DCOIT), on barrier function and mitochondrial bioenergetics using murine brain endothelial cell line (bEND.3)

Isothiazolinone (IT) biocides are potent antibacterial substances used as preservatives and disinfectants. These biocides exert differing biocidal effects and display environmental stability based upon chemical structure. In agreement with our recent study reporting that 2-n-octyl-4-isothiazolin-3-one (OIT) induced dysfunction of the blood-brain barrier (BBB), the potential adverse health effects of two IT biocides 1,2-benzisothiazolin-3-one (BIT) and 4,5-dichloro-2-n-octyl-isothiazolin-3-one (DCOIT) were compared using brain endothelial cells (ECs) derived from murine brain endothelial cell line (bEND.3). BIT possesses an unchlorinated IT ring structure and used as a preservative in cleaning products. DCOIT contains a chlorinated IT ring structure and employed as an antifouling agent in paints. Data demonstrated that DCOIT altered cellular metabolism at a lower concentration than BIT. Both BIT and DCOIT increased reactive oxygen species (ROS) generation at the mitochondrial and cellular levels. However, the effect of DCOIT on glutathione (GSH) levels appeared to be greater than BIT. While mitochondrial membrane potential (MMP) was decreased in both BIT- and DCOIT-exposed cells, direct disturbance in mitochondrial bioenergetic flux was only observed in BIT-treated ECs. Taken together, IT biocides produced toxicity in brain EC and barrier dysfunction, but at different concentration ranges suggesting distinct differing mechanisms related to chemical structure.

Antimicrobial coatings for environmental surfaces in hospitals: a potential new pillar for prevention strategies in hygiene

Recent reports provide evidence that contaminated healthcare environments represent major sources for the acquisition and transmission of pathogens. Antimicrobial coatings (AMC) may permanently and autonomously reduce the contamination of such environmental surfaces complementing standard hygiene procedures. This review provides an overview of the current status of AMC and the demands to enable a rational application of AMC in health care settings. Firstly, a suitable laboratory test norm is required that adequately quantifies the efficacy of AMC. In particular, the frequently used wet testing (e.g. ISO 22196) must be replaced by testing under realistic, dry surface conditions. Secondly, field studies should be mandatory to provide evidence for antimicrobial efficacy under real-life conditions. The antimicrobial efficacy should be correlated to the rate of nosocomial transmission at least. Thirdly, the respective AMC technology should not add additional bacterial resistance development induced by the biocidal agents and co- or cross-resistance with antibiotic substances. Lastly, the biocidal substances used in AMC should be safe for humans and the environment. These measures should help to achieve a broader acceptance for AMC in healthcare settings and beyond. Technologies like the photodynamic approach already fulfil most of these AMC requirements.

Safer and Greener Polymer Demonstrations for STEM Outreach

Polymer demonstrations have become increasingly important within science, technology, engineering, and math education curricula. These demonstrations not only afford the opportunity to introduce students to polymers but also provide an avenue to educate students about the impact polymers have on the planet. Despite the educational value and recreational enjoyment polymer demonstrations can provide, there are serious health and environmental hazards associated with some of the historically common polymer demonstrations that should be addressed. This Perspective describes the benefits and consequences of the historically common polymer "slime" and "silly putty" demonstrations and then details alternatives that can replace them. Finally, a Methods section of healthier and safer polymer demonstrations with detailed protocols is included.

Contact dermatitis to hair cosmetics: Current diagnostic recommendations

Hair cosmetics such as shampoos, hair dyes, bleaching agents or hair straightening creams contain frequent contact allergens. These can lead to allergic contact dermatitis especially in hairdressers, but also in their customers and in others who use hair products at home. While hairdressers suffer mainly from hand dermatitis, in customers and home-users, dermatitis primarily affects the head, neck and face. In this mini-review, we propose a diagnostic algorithm in two steps, based on patch testing, that can be used for the assessment of suspected hair product-induced contact dermatitis. In a first step, we recommend testing the German Contact Allergy Group (DKG) standard series, DKG ointment series, DKG preservative series, DKG hairdresser series, DKG fragrance series as well as (especially in hairdressers) the DKG rubber series. In a second step, if the culprit allergen cannot be identified with the help of the standardized test series and there is a well-founded suspicion, testing the patient's own products, such as shampoos, hair sprays and hair dyes, is recommended.

Probabilistic risk assessment of preservatives in dishwashing detergents and wet wipes for Korean consumers

Preservatives are essential additives in dishwashing detergents and wet wipes. Ensuring the safe use of preservatives in products is important for public health, as some preservatives are associated with health issues. In this study, the content of 12 preservatives in 105 dishwashing detergents and 105 wet wipes was determined, where these compounds are commonly found, among consumer products. A realistic exposure estimation was considered by using Korean consumer-specific exposure parameters for adults and babies. A probabilistic risk assessment was conducted by applying the Monte Carlo simulation method. Benzoic acid (41%) and cetylpyridinium chloride (30%) were the most commonly used preservatives in dishwashing detergents and wet wipes, respectively, although their content in different products (benzoic acid: 0.28-19.4 mg/g in dishwashing detergents; cetylpyridinium chloride: 0.003-0.64 mg/g in wet wipes) varied widely. The calculated median and upper-limit margin of safety (MOS) values related to systemic health effects and skin sensitization from exposure to preservatives largely exceeded the target MOS, which confirmed the safety of the products. Exposure to preservatives from wet wipes was several times higher in babies than in adults. Sensitivity analysis revealed that the amount of the product used, frequency of use, and weight fraction of the preservative were the major contributors to the exposure to preservatives from dishwashing detergents and wet wipes.

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.

Age-related differences in patch testing results among children: Analysis of North American Contact Dermatitis Group Data, 2001-2018

BACKGROUND

An updated understanding of allergic contact dermatitis is needed, particularly in children.

OBJECTIVES

To compare positive and clinically relevant reactions in children versus adults referred for patch testing.

METHODS

Retrospective analysis of 1871 children and 41,699 adults from the North American Contact Dermatitis Group (NACDG) from 2001-2018.

RESULTS

Both final diagnosis of allergic contact dermatitis (55.2% versus 57.3%; chi square, P = .0716) and prevalence of ≥ 1 currently relevant reaction to a NACDG screening allergen (49.2% vs 52.2%; P = .1178) were similar between children and adults. Currently in children, the most common relevant allergens were nickel sulfate (17.3%), hydroperoxides of linalool (7.8%), methylisothiazolinone (7.7%), cobalt chloride (7.0%), and fragrance mix I (4.9%). Approximately a fifth of children had a positive reaction to a non-NACDG allergen.

CONCLUSION

Over half of children referred for patch testing were diagnosed with allergic contact dermatitis. The most common relevant allergens in children were nickel sulfate, cobalt chloride, and hydroperoxides of linalool. Twenty percent of children had at least 1 positive reaction to allergens/substances not on the NACDG screening series, underscoring the need for comprehensive testing.

Controversy around parabens: Alternative strategies for preservative use in cosmetics and personal care products

Parabens usage as preservatives in cosmetics and personal care products have been debated among scientists and consumers. Parabens are easy to production, effective and cheap, but its safety status remains controversial. Other popular cosmetics preservatives are formaldehyde, triclosan, methylisothiazolinone, methylchloroisothiazolinone, phenoxyethanol, benzyl alcohol and sodium benzoate. Although their high antimicrobial effectiveness, they also exhibit some adverse health effects. Lately, scientists have shown that natural substances such as essential oils and plant extracts present antimicrobial potential. However, their use in cosmetic is a challenge. The present review article is a comprehensive summary of the available methods to prevent microbial contamination of cosmetics and personal care products, which can allow reducing the use of parabens in these products.