Kathon CG: a review

Risk management of skin sensitisers: A commentary

Historically, allergic contact dermatitis (ACD) to chemicals encouraged hazard identification improvements, more sophisticated risk assessment and implementation of regulatory strategies, including banning of specific sensitising substances. The validation process applied to hazard identification methods demonstrates their accuracy; their use to characterise sensitiser potency facilitates quantitative and transparent risk assessment. Diagnostic patch testing at dermatology clinics worldwide delivers feedback showing where risk assessment/management has been insufficient or did not target the exposure of concern, thereby facilitating improvements. When urgent action to protect human health was required, regulations limited/banned, specific skin sensitisers. This can be seen in practice with the fragrance industry, a known source of ACD, thus requiring risk management, usually restrictions to limit allergy induction, and very rarely specific bans on ingredients. Experience and development of more sophisticated tools, e.g. to assess aggregate exposure from multitude of consumer product types, has led to repeated adaptation of risk assessment and promulgation of updated fragrance use limits. Although targeted control may not always lead to rapid change in the overall clinical picture, it is preferable to a blanket undifferentiated regulatory control of all sensitisers, resulting in unwarranted restrictions for many uses of no health concern, with consequent substantial socio-economic impacts.

Review of Inhalation Health Risks Involving Chloromethylisothiazolinone (CMIT) and Methylisothiazolinone (MIT) Used as Disinfectants in Household Humidifiers

The association between lung injury and exposure to humidifier disinfectant (HD) containing a mixture of chloromethylisothiazolinone (CMIT) and methylisothiazolinone (MIT) has been controversial in South Korea. This study conducts a literature review in order to evaluate the likelihood of CMIT/MIT reaching the lower part of the respiratory tract and causing lung injury. A literature review focused on the inhalation risk of HD containing a mixture of CMIT and MIT. The major contents included the physicochemical properties of CMIT and MIT contained in HDs and methodological reviews on substance analysis, toxicity tests and clinical cases. HD products marketed in South Korea have been reported to contain approximately 1-2% CMIT and 0.2-0.6% MIT along with magnesium nitrate (20-25%), magnesium chloride (0.2-1.0%), and water (70-75%). The types of CMIT and MIT dispersed into the air and deposited in the respiratory tract are assumed to be either gaseous substances or nanoparticles mixed with magnesium salts. The result of the literature review including clinical cases of lung injury among CMIT/MIT HD product users, demonstrated that these chemicals likely reach the lower respiratory tract and accordingly cause lung injury. A number of humidifier disinfectant-associated lung injury cases with clinical evidence should be prioritized in risk assessment of HD containing CMIT and MIT, even though there might be insufficient evidence in all related areas, including inhalation exposure assessment studies, animal testing, and epidemiological studies.

Patch Testing With Tocopherol and Tocopherol Acetate: The North American Contact Dermatitis Group Experience, 2001 to 2016

BACKGROUND

Vitamin E (tocopherol) a naturally occurring mixture of antioxidants commonly used in topical skin care products, may cause allergic contact dermatitis.

OBJECTIVE

The aim of this study was to characterize positive patch test reactions to tocopherol and tocopherol acetate.

METHODS

This is a retrospective analysis of North American Contact Dermatitis Group patch test data to tocopherols (DL-α-tocopherol 100% and/or DL-α-tocopherol acetate 100%) from 2001 to 2016.

RESULTS

Of the 38,699 patients patch tested to tocopherol and/or tocopherol acetate, 349 (0.9%) had positive reactions; of these, 87.6% were currently relevant. Most (51.4%) were weak (+) and/or not related to occupation (99.1%). Compared with tocopherol-negative patients, tocopherol-positive individuals were more likely to be female (72.5% vs 67.2%, P = 0.0355), have a final primary diagnosis of allergic contact dermatitis (74.2% vs 52.6%, P < 0.0001), and have dermatitis in a scattered generalized distribution (23.8% vs 18.2%, P = 0.0072); they were also less likely to have hand involvement (16.6% vs 22.3%, P = 0.0064). The most common source of tocopherol was personal care products, especially moisturizers.

CONCLUSIONS

Positive patch test reactions to tocopherols were relatively rare given their widespread use. When positive, current clinical relevance was high. Tocopherol-positive patients were more likely to be female and presented with dermatitis on the face or in a scattered generalized pattern.

Evaluation of the effectiveness, safety, and feasibility of 9 potential biocides to disinfect acidic landfill leachate from algae and bacteria

This study evaluates 9 biocides as disinfectants against microbiological contaminants, specifically, microalgae and E. coli, while assessing their safety and environmental impact. Specifically, the biocide effectiveness and corresponding generation of halogenated compounds is assessed in a real contaminated groundwater receiving acidic leachate from a phosphogypsum landfill. Oxidizing agents are investigated, namely, hypochlorite, peracetic acid, hydrogen peroxide, chlorine dioxide, and persulfate, together with electrophilic biocides, namely, 2,2-dibromo-2-cyanoacetamide and (chloro-) methylisothiazolinone. In addition, a novel disinfection approach is assessed by applying reducing agents, namely, sulfite and metabisulfite. The disinfection mechanism and the formation of halogenated compounds are discussed on the basis of the mode of action and of the molecular structure of each biocide. Overall, the results show that an optimal dosage of the biocides exists to minimize the formation of harmful compounds in water while maximizing disinfection, especially for hypochlorite and peracetic acid. This dosage was between 0.03 mM and 0.15 mM depending on the biocide. The safety of electrophilic biocides is found to be associated to their molecular structure rather than their mode of action. Hydrogen peroxide, MIT, and metabisulfite are the most promising disinfectants in the contaminated groundwater matrix of interest since no halogenated by-products are detected upon successful disinfection, while they are able to completely inactivate bacteria and remove over the 80% of microalgae in the selected matrix. In particular, metabisulfite represents a highly promising biocide, owing to its low environmental and health impacts, as well as economic feasibility (estimated reagent cost ~0.002 € per cubic meter of treated water).

Simultaneous Determination of Isothiazolinones and Parabens in Cosmetic Products Using Solid-Phase Extraction and Ultra-High Performance Liquid Chromatography/Diode Array Detector

Isothiazolinones methylisothiazolinone (MI) and methylchloroisothiazolinone (MCI), and parabens methylparaben (MP), ethylparaben (EP), propylparaben (PP) and butylparaben (BP) are the most common synthetic preservatives. They are all known to be potential skin allergens that lead to contact dermatitis. Thus, the identification of these unsafe chemicals in cosmetic products is of high importance. In the present study, solid-phase extraction (SPE) based on HyperSep reversed-phase C8/benzene sulfonic acid ion exchanger (HyperSep C8/BSAIE) and Sep-Pak C18 sorbents, and ultra-high performance liquid chromatography/diode array detector (UHPLC/DAD) were optimized for the simultaneous determination of MI, MCI, MP, EP, PP and BP in cosmetic products. HyperSep C8/BSAIE and UHPLC/DAD with the eluting solvent mixture (acetonitrile/methanol, 2:1, v/v) and detection wavelength (255 nm) were found to be the optimal conditions, respectively. The method illustrates the excellent linearity range (0.008–20 μg/mL) with coefficient of determination (R², 0.997–0.999), limits of detection (LOD, 0.001–0.002 μg/mL), precision in terms of relative standard deviation (RSD < 3%, intra-day and <6%, inter-day) when examining a standard mixture at low (0.07 µg/mL), medium (3 µg/mL) and high (15 µg/mL) concentrations. A total of 31 cosmetic samples were studied, achieving concentrations (MI, not detected (nd)-0.89 µg/g), (MCI, nd-0.62 µg/g), (MP, nd-6.53 µg/g), (EP, nd-0.90 µg/g), (PP, nd-9.69 µg/g) and (BP, nd-17.80 µg/g). Recovery values ranged from 92.33 to 101.43% depending on the types of sample. To our knowledge, this is the first specific method which covers the theme and describes background amounts of such preservatives in cosmetics.

Graphene oxide enhanced ozonation of 5-chloro-2-methyl-4-isothiazolin-3-one: Kinetics, degradation pathway, and toxicity

Kathon is among the most common non-oxidative biocides, containing 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT) and methylisothiazolone (MIT) as the active ingredients. In our previous work, MIT was shown to be efficiently removed by ozonation. In this work, we found that ozonation didn't readily degrade CMIT. Rate constants [Formula: see text] and k_·OH,CMIT, determined to be 6.43 L mol^-1 s^-1 and 7.8 × 10⁹ L mol^-1 s^-1, indicated that hydroxyl radicals played a more important role than ozone molecule in the CMIT ozonation which was also proved by the significant inhibition (55.7 %) when adding t-butanol (TBA). Graphene oxide (GO) greatly enhanced the CMIT ozonation, and degradation efficiency raised from 15 % to 100 % after 10 min through the increased production of hydroxyl radical. Basic conditions benefited the CMIT degradation compared with acidic and neutral conditions by promoting ozone decomposition and hydroxyl radical generation, while high carbonate and humic acid concentrations had slight influence on the CMIT degradation. In spite of the complex water matrix, CMIT degradation by GO enhanced ozonation was applicable in reverse osmosis concentrate (ROC). Based on the identification of the inorganic and organic products, a possible CMIT degradation pathway was proposed. However, CMIT transformation products still showed toxicity to Photobacterium phosphoreum and Daphnia magna even after a longer ozonation time.

Devising a Tier-based Skin Sensitisation Screening Strategy for Personal Care and Cosmetic Products

Concerns regarding the use of potential skin sensitisers in personal care and cosmetic products continue to grow. The goal of this study was to develop a proof-of-concept tier-based screening strategy for the assessment of skin sensitisation potential by using non-animal methodologies. As a case example, this screening framework was applied to three WEN® by Chaz Dean cleansing conditioners. The first tier of testing utilised the Organisation for Economic Co-operation and Development (OECD) Quantitative Structure Activity Relationship Toolbox profiler to evaluate the skin sensitisation potential of individual ingredients within the formulation; a literature review was performed on the substances that generated in silico alerts. Tier 2 testing utilised the OECD in chemico Test Guideline (TG) 442C to evaluate these substances. Tier 3 testing adapted OECD TG442C to evaluate the formulated product. The literature review on the four substances that generated in silico alerts revealed that they were not sensitising at the concentrations reported in the formulated products. Tier 2 testing demonstrated that these substances were not sensitising at the concentrations tested. Finally, Tier 3 testing revealed that the evaluated cleansing conditioners had low mean percentage peptide depletion at the concentrations tested. Together, the results obtained suggest that the products tested are unlikely to induce skin sensitisation under the given experimental conditions. These findings are in agreement with other in vitro and clinical studies. The proposed tier-based testing approach may be used as a conceptual framework for the prospective safety screening of other personal care and cosmetic products. However, to establish the validity of the proposed testing strategy, further studies must be performed, including comparisons with established models.

Inhaled Kathon may induce eosinophilia-mediated disease in the lung

In 2011, a link between humidifier disinfectants and patients with idiopathic pulmonary fibrosis was identified in Korea, and Kathon was suggested as one of the causative agents. In this study, Kathon induced apoptotic cell death along with membrane damage at 24 h post-exposure. Additionally, on day 14 after a single instillation with Kathon, the total number of pulmonary cells and the levels of TNF-α, IL-5, IL-13, MIP-1α, and MCP-1α clearly increased in the lung of mice. The proportion of natural killer cells and eosinophils were significantly elevated in the spleen and the bloodstream, respectively, and the level of immunoglobulin (Ig) A, but not IgG, IgM, and IgE, dose-dependently increased. Therefore, we suggest that inhaled Kathon may induce eosinophilia-mediated disease in the lung by disrupting homeostasis of pulmonary surfactants. Considering that eosinophilia is closely related to cancer and fibrosis, further studies are needed to understand the relationship between them.

Repeated Vaginal Exposures to the Common Cosmetic and Household Preservative Methylisothiazolinone Induce Persistent, Mast Cell-Dependent Genital Pain in ND4 Mice

A history of allergies doubles the risk of vulvodynia—a chronic pain condition of unknown etiology often accompanied by increases in numbers of vulvar mast cells. We previously established the biological plausibility of this relationship in mouse models where repeated exposures to the allergens oxazolone or dinitrofluorobenzene on the labiar skin or inside the vaginal canal of ND4 Swiss Webster outbred mice led to persistent tactile sensitivity and local increases in mast cells. In these models, depletion of mast cells alleviated pain. While exposure to cleaning chemicals has been connected to elevated vulvodynia risk, no single agent has been linked to adverse outcomes. We sensitized female mice to methylisothiazolinone (MI)—a biocide preservative ubiquitous in cosmetics and cleaners—dissolved in saline on their flanks, and subsequently challenged them with MI or saline for ten consecutive days in the vaginal canal. MI-challenged mice developed persistent tactile sensitivity, increased vaginal mast cells and eosinophils, and had higher serum Immunoglobulin E. Therapeutic and preventive intra-vaginal administration of Δ⁹-tetrahydrocannabinol reduced mast cell accumulation and tactile sensitivity. MI is known to cause skin and airway irritation in humans, and here we provide the first pre-clinical evidence that repeated MI exposures can also provoke allergy-driven genital pain.

Mixture Toxicity of Methylisothiazolinone and Propylene Glycol at a Maximum Concentration for Personal Care Products

Methylisothiazolinone (MIT) has been used in combination with methylchloroisothiazolinone (CMIT) for cosmetic products such as shampoo, body lotion, and skin care products. The mixture of CMIT/MIT has been found to cause allergic contact dermatitis and is thus no longer permitted for use as a preservative in leave-on cosmetics. However, MIT itself was approved as a stand-alone preservative at a maximum concentration of 100 ppm as the toxicity was derived from CMIT rather than MIT. However, in many countries, allergic skin irritation caused by MIT remains a social concern. In this study, skin irritation was assessed for the presence of MIT, propylene glycol, and their mixture using a 3D human skin model EpiDerm™. Although non-diluted MIT causes serious skin toxicity, skin irritation was not observed at a concentration of 100 ppm, the maximum permissible level for cosmetics and personal care products according to European regulations. Propylene glycol, the most widely used vehicle for MIT, did not cause skin irritation in the 3D skin model. The results are expected to provide information for regulatory policies and guidelines on the use of biocides in consumer products.

In-service characterization of a polymer wick-based quasi-dry electrode for rapid pasteless electroencephalography

A novel quasi-dry electrode prototype, based on a polymer wick structure filled with a specially designed hydrating solution is proposed for electroencephalography (EEG) applications. The new electrode does not require the use of a conventional electrolyte paste to achieve a wet, low-impedance scalp contact. When compared to standard commercial Ag/AgCl sensors, the proposed wick electrodes exhibit similar electrochemical noise and potential drift values. Lower impedances are observed when tested in human volunteers due to more effective electrode/skin contact. Furthermore, the electrodes exhibit an excellent autonomy, displaying an average interfacial impedance of 37±11 kΩ cm2 for 7 h of skin contact. After performing bipolar EEG trials in human volunteers, no substantial differences are evident in terms of shape, amplitude and spectral characteristics between signals of wick and commercial wet electrodes. Thus, the wick electrodes can be considered suitable to be used for rapid EEG applications (electrodes can be prepared without the presence of the patient) without the traditional electrolyte paste. The main advantages of these novel electrodes over the Ag/AgCl system are their low and stable impedance (obtained without conventional paste), long autonomy, comfort, lack of dirtying or damaging of the hair and because only a minimal cleaning procedure is required after the exam.

Skin sensitization

Skin sensitization associated with allergic contact dermatitis is a common health problem and is an important consideration for toxicologists in safety assessment. Historically, in vivo predictive tests have been used with good success to identify substances that have the potential to induce skin sensitization, and these tests formed the basis of safety evaluation. These original tests are now being replaced gradually either by in vitro assays or by further refinements of in vivo methods such as the local lymph node assay. Human data have also been available to inform classification decisions for some substances and have been used by risk managers to introduce measures for exposure reduction. However, humans encounter hazards in the context of exposure rather than in the form of intrinsic hazards per se, and so in this article, we have examined critically the extent to which human data have been used to refine classification decisions and safety evaluations. We have also evaluated information on the burden of human allergic skin disease and used this to address the question of whether, and to what extent, the identification and evaluation of skin sensitization hazards has led to an improvement of public and/or occupational health.

Methylisothiazolinone: dermal and respiratory immune responses in mice

Methylisothiazolinone (MI), a widely used chemical preservative in industrial and household products, and cosmetics, has been associated with allergic contact dermatitis. However, the asthmogenic capacity of MI is currently unknown. In this study, we investigated the capacity of MI to elicit asthma-like responses in a validated mouse model. On days 1 and 8, mice (C57Bl/6 and BALB/c) were dermally treated with MI or vehicle on each ear. On day 15, mice received a single intranasal challenge with MI or vehicle. Immediately after the challenge, the early ventilatory response was measured using a double chamber plethysmograph. One day later, airway hyperreactivity, pulmonary inflammation and immune-related parameters were assessed. Dermal treatment with MI in both C57Bl/6 and BALB/c mice induced increased T- and B-cell proliferation in the auricular lymph nodes, along with IFN-γ production and limited increases in total serum IgE, confirming dermal sensitization. An airway challenge with MI led to an early ventilatory response (decreased breathing frequency), indicative for acute sensory irritation. However, 24h later no allergic respiratory response (no airway hyperreactivity (AHR) nor pulmonary inflammation) was found in either mouse strains. Our study indicates that MI can be classified as a strong dermal sensitizer and irritant, but not an asthmogen after initial dermal sensitization, followed by an airway challenge.

The Myeloid U937 Skin Sensitization Test (U-SENS) addresses the activation of dendritic cell event in the adverse outcome pathway for skin sensitization

The U-SENS™ assay, formerly known as MUSST (Myeloid U937 Skin Sensitization Test), is an in vitro method to assess skin sensitization. Dendritic cell activation following exposure to sensitizers was modelled in the U937 human myeloid cell line by measuring the induction of the expression of CD86 by flow cytometry. The predictive performance of U-SENS™ was assessed via a comprehensive comparison analysis with the available human and LLNA data of 175 substances. U-SENS™ showed 79% specificity, 90% sensitivity and 88% accuracy. A four laboratory ring study demonstrated the transferability, reliability and reproducibility of U-SENS™, with a reproducibility of 95% within laboratories and 79% between-laboratories, showing that the U-SENS™ assay is a promising tool in a skin sensitization risk assessment testing strategy.

Allergic Contact Dermatitis to Cosmetics

Cosmetics are used to enhance one's appearance and are used by women worldwide. This article reviews the epidemiology, clinical features, and management of cosmetic allergic contact dermatitis. Additionally, several important cosmetic-related allergens are discussed.

Hypersensitivity to preservatives

Preservatives are biocidal chemicals added to cosmetics, topical medicaments, consumer goods, foods, and industrial products to protect them against microbial spoilage and to protect the consumer against infection. The ideal preservative, both effective and devoid of irritant or sensitizing potential, is still to be discovered. The present paper reviews the most important classes of preservatives, namely parabens, formaldehyde-releasers, and isothiazolinones. The author also discusses newer agents such as Euxyl K 400 and isopropynyl butylcarbamate. Each preservative is described in terms of chemical and physical characteristics, antimicrobial efficacy, exposure, cutaneous adverse reactions, patch testing concentrations, patterns of cross-reactions, and reported rates of sensitization. The history of preservatives goes back to the 1930s, and ironically, the parabens, which the industry has sought to replace with "safer" alternatives, are still the most frequently used biocides in cosmetics and appear to be far less sensitizing than most of the newer agents.

Cosmetic dermatitis - current perspectives

BACKGROUND

Increasing use of cosmetics by modern society has contributed alarming to an rise in the incidence of cosmetic dermatitis (CD). The causative agents are skin, hair, nail and eye cosmetics. Reported cases of cosmetic dermatitis represent only the tip of the iceberg, as most patients who experience an adverse reaction to cosmetics do not consult a physician but discontinue using the suspected items.

METHODS

A comprehensive history followed by adequate clinical examination and patch test is important to diagnose reaction to cosmetics. In addition other tests like Repeated Open Application Test (ROAT), usage test, elimination test and safety test are important, as many cosmetics and their ingredients are either weak allergens or irritants.

RESULTS

A wide variety of adverse reactions to cosmetics are seen which are of both irritant and allergic type. Pattern of CD varies in different parts of the world depending upon the type and frequency of different cosmetics used. Reactions are more commonly seen in females of younger age and the face is the most common site.

CONCLUSIONS

Though prevention is better than cure, but cosmetics have definitely infiltrated into our life style. We cannot prevent use of cosmetics but can only limit their use by educating their users and helping them in judicious selection of the required cosmetics.

[Contact sensitization to external agents]

The following review describes contact sensitization to topically applied medications--especially topical dermatological agents--and to external agents in the broadest sense. Particularly skin care products constitute a special source for sensitization due to their widespread use. Especially fragrances and preservatives in cosmetics play an important global role in eliciting contact allergies. Because of the extremely broad spectrum covered by the active and adjuvant ingredients contained in external agents, the following discussion focuses on specific substance groups.

Evaluation of the role of contact sensitization and photosensitivity in the pathogenesis of poikiloderma of Civatte

BACKGROUND

Poikiloderma of the face and neck (Civatte) is a rather common, indolent, chronic dermatosis, most often affecting menopausal females. Cumulative excessive sun exposure, a phototoxic or a photoallergic reaction, hormonal changes of menopause and genetic factors have all been incriminated in its obscure aetiopathogenesis.

OBJECTIVE

To evaluate the role of contact sensitization and photosensitivity in the pathogenesis of poikiloderma of Civatte (PC).

METHODS

Thirty-two patients (24 females and eight males, age range 38-74 years) with PC were patch tested with the European standard series and the fragrance series, and were photopatch tested with the photoallergens series. Additionally, photo-testing with a monochromator was performed.

RESULTS

Thirteen of 32 patients (40.62%) had one or more positive reactions to allergens of the standard series. Eight patients (25%) had positive reactions to fragrance mix and/or Balsam of Peru, which are included in the standard series, or to allergens of the fragrance series. Nickel sulphate was the single most common cause of contact sensitization (18.75%) among our patients. Ninety-seven subjects, who were patch tested with the standard series for suspected allergic contact dermatitis of the face and/or neck, served as age, sex and site controls. Of these, nine (9.27%) had one or more positive reactions to fragrance compounds. Statistical analysis showed a statistically significant difference in the frequency of positive reactions to fragrances between the PC group and the control group (chi2 value = 3.91, P < 0.05). In contrast, none of the PC patients had a positive photopatch test for the allergens included in the photoallergens series. The estimated minimal erythemal dose for the PC group was in all cases within normal limits for all wavelengths of ultraviolet (UV) radiation examined.

CONCLUSIONS

Contact sensitization, mostly to perfume ingredients, may develop in PC, possibly playing a pathogenetic part, at least in a subset of patients. Despite negative results of photopatch testing, an allergic photo-contact reaction cannot be definitely excluded. PC seems not to be a photosensitivity disorder of the type of chronic actinic dermatitis. UV radiation-induced dermal connective tissue changes are the predominant histological feature of PC, leading to telangiectasia due to loss of vascular support. Reticular pigmentation may result from a delayed hypersensitivity reaction to perfume and/or cosmetic ingredients. Patch testing with the standard series and avoidance of documented allergens may be of value in patients with PC.

In vitro induction of apoptosis vs. necrosis by widely used preservatives: 2-phenoxyethanol, a mixture of isothiazolinones, imidazolidinyl urea and 1,2-pentanediol

Preservatives are added to many final products, such as detergents, cosmetics, pharmaceuticals and vaccines. We conducted an in vitro investigation of the apoptosis- and necrosis-inducing potential of brief applications (10 min) of four common preservatives: ethylene glycol monophenyl ether, 2-phenoxyethanol (EGPE), imidazolidinyl urea (IMU), a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one (CMI/MI), and 1,2-pentanediol, a "preservative-non-preservative" best known as pentylene glycol. Using HL60 cells, we monitored the kinetics of cell toxicity with the MTT test and analysed extranuclear end points of apoptosis, i.e. phosphatidylserine exposure and nuclear fragmentation. Preservative treatment resulted in a dose-dependent decrease of cell viability. The mode of cell death was dose-dependent: necrosis occurred at high concentrations while apoptosis, shown by DNA laddering, DNA sub-diploid peak and caspase-3 activation, occurred at lower concentrations 0-24hr after exposure to a single dose: CMI/MI induced apoptosis at low concentrations (0.001-0.01%) and necrosis at high concentrations (0.5-0.1%); IMU and EGPE required higher concentrations to induce apoptosis (IMU 0.01-0.1% and EGPE 0.01-0.5%) or necrosis (IMU 0.5-1% and EGPE only at 1%). PG induced apoptosis only at 5%. Externalization of PS, a hallmark of apoptosis, occurred early in HL60 treated with low concentrations of CMI/MI and EGPE and was concomitant with the subdiploid peak in HL60 treated with PG. However, it did not occur in HL60 treated with IMU. In conclusion, at appropriate concentrations, each of the four preservatives modulates the apoptotic machinery by a caspase-dependent mechanism. Thus, apoptosis could be a good parameter to evaluate the cytoxicity of these chemical compounds.

Allergen-induced changes in interleukin 1 beta (IL-1 beta) mRNA expression by human blood-derived dendritic cells: inter-individual differences and relevance for sensitization testing

The development of in vitro methods for the identification of skin sensitizers based upon analysis of Langerhans cell (LC) function has been constrained by the fact that these cells represent only a minority population in the skin that, once isolated, alter their phenotype spontaneously and rapidly. Methods have been developed recently that allow the expansion in culture using appropriate cytokine conditions of LC-like dendritic cells (DCs) from certain tissues, including human peripheral blood. It has been demonstrated that culture of human blood-derived LC-like cells with selected potent contact allergens such as 2,4-dinitrofluorobenzene (DNFB) stimulates selective phenotypic changes, including the up-regulation of interleukin 1 beta (IL-1 beta) mRNA expression, under conditions where skin irritants are without effect. However, in our own previous investigations, we have observed that there appear to be differences between blood donors with respect to the responsiveness of DCs to DNFB-induced changes in IL-1 beta expression, differences that could compromise the utility of this approach as a screening method for contact allergens. We have therefore investigated donor variability in DC responsiveness to a panel of known human contact allergens (DNFB; paraphenylene diamine, PPD; methyl- chloroisothiazolinone/methylisothiazolinone, CMIT), to the skin irritant benzalkonium chloride and to the mitogen phorbol myristate acetate (PMA). Dendritic cells derived from all donors expressed IL-1 beta mRNA constitutively. Treatment of DCs isolated from donors with a responder phenotype to DNFB with PPD or CMIT resulted also in up-regulation of IL-1 beta mRNA expression, although such changes were always comparatively modest, generally resulting in a twofold induction compared with vehicle-treated controls. Dendritic cells derived from donors with a non-responder phenotype to DNFB failed also to respond to these additional contact allergens under conditions where the mitogen PMA caused similar increases in IL-1 beta expression to those observed for allergen-responsive donors. Benzalkonium chloride failed to provoke changes in the expression of this cytokine in any donor examined, irrespective of their responder phenotype. The temporal stability of the responder/non-responder DC phenotype was confirmed, with stable phenotypes with respect to DNFB-induced changes in IL-1 beta mRNA expression observed over a period of some 18 months. Fifty per cent (6/12) of donors tested over this period displayed a responder phenotype. These data demonstrate that chemical allergens do stimulate consistent changes in IL-1 beta mRNA expression in the proportion of donors who have a responsive phenotype, and that such responses are apparently selective for allergen using the relatively narrow range of materials assessed to date. However, the modest response to very strong contact allergens, coupled with the difficulties of responder/non-responder phenotypes, means that in its present form this approach does not lend itself to the routine assessment of skin sensitizing activity.

Influence of application vehicle on skin sensitization to methylchloroisothiazolinone/methylisothiazolinone: an analysis using the local lymph node assay

The murine local lymph node assay (LLNA) is a method for the identification of skin sensitizing chemicals in which activity is measured as a function of proliferative responses induced in draining lymph nodes following topical exposure of mice to the test material. More recently, the LLNA has also been used for the determination of relative skin sensitizing potency based upon the mathematical derivation of an EC3 value, this being the estimated concentration of test chemical necessary to provoke a 3-fold increase in lymph-node cell-proliferative activity compared with concurrent vehicle-treated controls. Here we describe the use of the LLNA to determine the influence of vehicle on the skin-sensitizing potency of methylchloroisothiazolinone/methylisothiazolinone (MCI/MI), the active ingredient of preservatives such as Kathon CG. To this end, LLNA responses to MCI/ MI were measured using the vehicles 4:1 acetone:olive oil (AOO), methyl ethyl ketone, dimethylsulfoxide, dimethylformamide, propylene glycol (PG) and acetone. It was found that the vehicle in which MCI/MI was applied had a substantial impact on activity, with derived EC3 values varying from 0.0049% with AOO to 0.048% with PG. With the other vehicles, EC3 values ranged from 0.0068 to 0.0076%. The skin sensitizing potency of MCI/MI as judged from LLNA responses is consistent with what is known of the requirements for sensitization in humans. It is proposed that the LLNA not only provides a method for determination of relative skin sensitizing potency, but is also appropriate for assessing the influence of vehicle matrix on sensitizing activity.

Patch testing with preservatives, antimicrobials and industrial biocides. Results from a multicentre study

Preservatives are biologically reactive substances, and their allergenic potential has been known for a long time. This study examined the role of different preservatives in a large number of patients with suspected allergic contact dermatitis. Patch test data and data from the patients' history were collected from the 24 departments participating in the Information Network of Departments of Dermatology from 1 January 1990 to 31 December 1994. Patch test data from 28,349 patients tested with preservatives of the standard series (SS), from 11,485 patients tested additionally with a preservative series (PS), and from 1787 patients tested with an industrial biocide tray (IB) were evaluated. Sensitization rates (standardized) of the SS preservatives were all > 1%, with thiomersal rating highest (5.3%), the parabens lowest (1.6%), and the remainder (chlormethylisothiazolinone/methylisothiazolinone, formaldehyde and methyldibromoglutaronitrile/phenoxyethanol (MDBGN/PE)) in the range of 2%. The most important allergens of the PS were, in women, alkylaminobenzoate (contained in milking fat) (2.5%), MDBGN/PE (2.2%), benzalkonium chloride (1.8%), chloracetamide (1.4%), diazolidinyl urea (1.3%), octylgallate (1.2%) and Bronopol (1.1%). In men rates differed only with regard to alkylaminobenzoate (0.9%). Patients tested with the IB series reacted most often to methylene-bis-thiocyanate (5%), but with a reaction index of -0.7, many reactions were most probably false positives. A further seven preservatives, mostly formaldehyde-releasers used in cutting fluids, gave sensitization rates of between 1% and 3%. Glutaraldehyde, not contained in the series but often tested additionally, showed a remarkable increase in sensitization during the study period. Health care personnel were frequently affected. Altogether, this study identified areas of concern within the different groups of preservatives. The overall impact of most of the preservatives on public health seems to be low, but for diagnostic reasons preservatives must be included in patch test series.

A bullous pemphigoid-like skin eruption after a chemical burn

Bullous pemphigoid is a blistering disorder characterized by antibody deposition in the lamina lucida of the basement membrane zone. In addition to the idiopathic form, there are many agents that have been implicated in inducing bullous pemphigoid or bullous pemphigoid-like lesions. We describe a patient who developed a bullous pemphigoid-like eruption after a chemical burn.

Methyldibromoglutaronitrile (Euxyl K 400): an important "new" allergen in cosmetics

Euxyl K 400 is a preservative system for cosmetics and toiletries that contains phenoxyethanol and methyldibromoglutaronitrile in a 4:1 ratio. In The Netherlands, Italy, and Germany, the prevalence of allergy to Euxyl K 400 has risen in the past 4 years and is currently 2% to 4% in patients suspected of having contact dermatitis. The allergenic ingredient is nearly always methyldibromoglutaronitrile. Causative products include both stay-on and rinse-off cosmetics and moistened toilet tissue. Because the causative products usually give false-negative reactions, the allergen, methyldibromoglutaronitrile, should be tested in all patients suspected of having cosmetic dermatitis and in those with perianal dermatitis. We suggest a test concentration of 0.3% to 0.5% in petrolatum.

Chloromethylisothiazolone/methylisothiazolone (CMI/MI) use test with a shampoo on patch-test-positive subjects. Results of a multicentre double-blind crossover trial

A randomized, multicentre, double-blind, 2-period crossover study with 2 shampoos was performed on subjects patch-test-positive to 100 ppm CMI/MI. One shampoo was preserved with 15 ppm a.i. CMI/MI, the other with 0.3% imidazolidinyl urea (IU). 27 subjects from 5 European dermatology clinics participated. 1 subject discontinued use after severe adverse reactions to the CMI/MI-preserved shampoo and did not evaluate the other shampoo. Another 2 subjects developed moderate symptoms with the CMI/MI-preserved shampoo and discontinued its use, but tolerated the IU-preserved shampoo for the full 2-week period. 2 subjects discontinued use after 1 or 2 washes after severe adverse reactions to the IU-preserved shampoo. 1 of these subjects tolerated the CMI/MI-preserved shampoo for 2 weeks without any untoward effects. However, the majority of subjects had negative findings on the scalp, face, neck, and hands for both shampoos. The physicians' global evaluation data indicated that shampoo with CMI/MI caused fewer skin problems than shampoo with IU (38% versus 27%, n.s.), with over 1/3 of the subjects (35%) having no skin problems with either preservative. The current study showed that most subjects previously sensitized to CMI/MI can successfully use shampoo preserved with CMI/MI. Since some subjects previously sensitized to CMI/MI, or possibly to IU, may develop clinical reactions, it would still be prudent for the clinician to advise alternative products to patients with sensitivity to a shampoo or cosmetic ingredient. Full ingredient labelling will ensure that this is possible. As the overall rate of adverse effects in sensitized individuals was low, studies of this nature should also be conducted for other allergens.(ABSTRACT TRUNCATED AT 250 WORDS)