Rapid increase in contact allergy to Kathon CG in Finland

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.

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.

6 Final Report on the Safety Assessment of Methylisothiazolinone and Methylchloroisothiazolinone

Methylisothiazolinone and Methylchloroisothiazolinone (MI/MCI) are heterocyclic organic compounds that are used in cosmetics as a broad spectrum preservative system.

MI/MCI was absorbed after oral administration and then was excreted in the urine or feces; storage in the tissues was minimal. Up to 62% of a single percutaneous dose was bound to the site of application 24 hours after exposure. The MI/MCI-CG bound to the skin had a 13.1-day half-life.

MI/MCI was moderately to highly toxic to rats, and highly toxic to rabbits when administered orally, and moderately toxic when applied dermally. MI/MCI was not a cumulative ocular irritant when tested at 55 ppm. The dermal irritation of MI/MCI was concentration dependent but nonirritating to rabbit skin at 560 ppm concentrations; this nonirritating concentration is well above the maximum recommended use concentration.

No treatment-related effects were observed in rats which received MI/MCI in oral doses up to 24.4 mg/kg/day for 2 weeks. Doses of MI/MCI up to 2.8 mg/kg/day applied dermally to rabbits, 5 days per week for 3 weeks, produced moderate irritation at the application site but no systemic toxicity. Dermal application of MI/MCI at doses up to 0.4 mg/kg/day for 3 months produced no systemic toxicity in rabbits. No toxicologically significant treatment-related effects were observed in rats or dogs at doses up to 30 and 28 mg/kg/day, respectively. The result of genotoxic testing of MI/MCI varied with the assay used. Dermal application of 400 ppm MI/MCI-CG, 3 times per week for 30 months, had no local or systemic tumorigenic effect in male mice.

MI/MCI administered by gavage to pregnant rabbits and rats at doses up to 13.3 mg/kg/day was toxic to the dam, embryo, and fetus; the compound was not teratogenic.

MI/MCI is a sensitizer however, the concentration of MI/MCI in cosmetic products which produced sensitization varies. The available human sensitization test data at concentrations of 50 ppm and above are not in agreement. MI/MCI-CG was not a sensitizer or photosensitizer at a concentration of 15 ppm.

It is concluded that Methylisothiazolinone/Methylchloroisothiazolinone may be safely used in “rinse-off” products at a concentration not to exceed 15 ppm and in “leave-on” cosmetic products at a concentration not to exceed 7.5 ppm. The stated safe use concentration refers to a mixture containing 23.3% Methylisothiazolinone and 76.7% Methylchloroisothiazolinone.

[Contact allergies in the German workforce : Data of the IVDK network from 2003-2013]

BACKGROUND

In Germany, occupational skin diseases rank first in the occupational skin disease statistics for many years. Especially, occupationally acquired contact allergies as well as multi-sensitization are the most important predictors for a poor prognosis and persistent eczema.

OBJECTIVES

To update the spectrum and sensitization frequencies of most frequent allergens from the standard series in Germany in patients with occupationally acquired type IV sensitizations in general and within different occupational groups.

METHODS

Data of all employed patients (age range: 16-68 years, n = 14234) patch tested between 2003 and 2013 in the German Departments of the Information Network of Departments of Dermatology (IVDK) and diagnosed occupationally acquired contact dermatitis after patch testing were analyzed. The control group was composed of all other patients (n = 31706) within the same time frame, in which occupationally acquired allergic contact dermatitis was negated explicitly.

RESULTS

The prevalence Ratio (PR; indicating risk) was significantly increased for: Thiuram-mix (PR 5.63 95 %CI 4.97-6.4), zinkdiethyldithiocarbamate (PR 6.22 95 %CI 4.76-8.22), mercaptobenzothiazole (MBT) (PR 3.88 95 %CI 3.09-4.89), mercapto-mix without MBT (PR 3.23 95 %CI 2.59-4.03), N-isopropyl-N'-phenyl-p-phenylene diamine (IPPD) (PR 2.3195 %CI 1.87-2.86), epoxy resin (PR 2.82 95 %CI 2.45-3.25), chloromethylisothiazolinone/methylisothiazolinone (MCI/MI) (PR 2.19 95 %CI 1.97-2.42) and compositae mix II (PR 2.05 95 %CI 1.45-2.89). They were the predominant occupational allergens and were at least associated with a doubled risk (PR ≥ 2.0) for acquiring occupationally allergic contact dermatitis. The highest risk increase was identified in employees in the health services, in agriculture, metal industry, food and service industry as well as building trades

CONCLUSIONS

A limited number of occupationally relevant allergens cause the majority of sensitizations in the workforce, if standard series allergens are concerned. Data analysis of national and international contact allergy data bases provide valuable information on sensitization rates and profiles in skin risk occupations to implement targeted prevention strategies. To diagnose occupational allergic contact dermatitis in individual cases additional testing of occupation related patch test series as well as patients' own products is commonly inevitable.

Isothiazolone emissions from building products

Adding biocides to dispersion products is a well-known practice to control microbial deterioration. Isothiazolones are among the most commonly used preservatives, in particular a mixture of 2-methyl-2H-isothiazol-3-one (MIT) and 5-chloro-2-methyl-2H-isothiazol-3-one (CIT). In recent years, for health reasons, due to its strong sensitizing effect, CIT has been replaced by 1,2-benzisothiazol-3-one (BIT). Furthermore, numerous products are now available for interiors containing the fungicidal active substance 2-octyl-2H-isothiazol-3-one (OIT). So far nearly nothing is known of the emission behavior of BIT and OIT. An analytical method was developed for these two isothiazolones and interior products containing BIT respectively OIT have been investigated in an emission chamber and in test rooms. The chamber tests revealed maximum concentrations of 6.7 μg OIT/m3, 1.9 μg BIT/m3, and 187 μg MIT/m3. Concentrations obtained in the test rooms were at levels up to 1.4 μg OIT/m3 and 29 μg MIT/m3. A noticeable finding was the very slight subsidence of OIT and BIT levels over several weeks. While MIT outgassed quickly, OIT in particular showed low concentrations, but prolonged evaporation.

Contact allergy epidemics and their controls

Contact dermatitis can be severe and lead to sick leave as well as significant healthcare expenses. The aim of this review is to present the published knowledge on 6 historical epidemics of contact allergy to apply this knowledge on the prevention and control of future contact allergy epidemics. A historical review is performed on nickel, chromium, methyl-chloro-iso-thiazolinone/methyl-iso-thiazolinone, methyl-di-bromo glucaro-nitrile, formaldehyde, and para-phenylenediamine. The first cases of contact dermatitis are mostly occupational, whereas consumer cases appear later. There is often a latency period from the first cases are observed until an epidemic occurs, and the problem is recognized. Finally, no one seems to take responsibility of dealing with the situation, and there are no attempts of regulation until an epidemic is consolidated among consumers for many years. Steps should be taken to prevent contact allergy epidemics. It is essential that dermatologist, scientists, administrators, and consumers organize and structure known methods to accelerate the control of emerging contact allergens.

An evaluation of dose/unit area and time as key factors influencing the elicitation capacity of methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) in MCI/MI-allergic patients

Methylchloroisothiazolinone and methylisothiazolinone (MCI/MI) contact allergy affects 1-3% of patch-tested patients in European centres. The aim of the present study was to evaluate the importance of the factors--time and concentration (dose/per unit area)--in the elicitation capacity by means of a repeated open application test (ROAT) experimental design. The study was designed as a double-blind, placebo-controlled, dose-response ROAT preceded by a diagnostic patch testing. 25 subjects with confirmed MCI/MI allergy and 10 healthy, non-MCI/MI allergic control subjects were exposed to 0.025 microg/cm2 (2 p.p.m.) of MCI/MI/unit area of the skin for 4 weeks. After a wash-out period of at least 4 weeks, the subjects were exposed to 0.094 microg/cm2 (7.5 p.p.m.) of MCI/MI/unit area of the skin for 4 weeks. The study showed the importance of both time and exposure in the elicitation process. It demonstrated that the elicitation threshold for MCI/MI is expected to be in the proximity of 0.025 microg/cm2 although it was not possible to establish a definitive elicitation threshold for MCI/MI in this study.

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.

Patch test reactions to cosmetic allergens in 1995-1997 and 2000-2002 in Finland - a multicentre study

Contact sensitivity to cosmetics is common, but the sensitizing chemicals vary between countries and study periods. The present survey aimed at revealing the recent trends in patch test sensitivity with cosmetic chemicals in Finland. We report a retrospective multicentre survey of patch test reactions focusing on cosmetic-related substances and comparing the test results in 1995-97 with those in 2000-02. The most striking increases in the frequency of the patch test sensitivity were found with balsam of Peru and propolis from 4.0% to 6.2% (P < 0.001) and from 0.5% to 1.4% (P < 0.001), respectively, whereas the most prominent decreases were found with methylchloro/methylisothiazolinone and chlorhexidine diglugonate from 2.4% to 1.3% (P < 0.001) and from 1.2% to 0.5% (P < 0.001), respectively. The level of patch test sensitivity to methyldibromo glutaronitrile increased, although not significantly, from 1.0% to 1.5%. An increasing tendency was also found with hair dye chemicals 4-aminophenol and toluene-2,5-diamine or toluene-2,5-diamine sulfate from 1.3% to 3.8% and from 1.4% to 5.2%, respectively, while such a tendency was not found among permanent wave chemicals. The sensitivity level of fragrance mix remained the same (6% - 7%). We conclude that surveys revealing the state of sensitivity to cosmetic chemicals should be performed periodically in different countries.

Contact sensitivity to preservatives in Turkey

This study was designed to evaluate the frequency of contact sensitivity to 14 common preservatives among patients with contact dermatitis in Turkey. From 2000 to 2004, 308 patients with the diagnosis of contact dermatitis were patch tested in the Department of Dermatology, Ankara University School of Medicine. All patients were patch tested with European standard series. In addition to the four preservatives included in the standard series, patients were also tested with DMDM hydantoin, imidazolidinyl urea, bromonitropropane diol, diazolidinyl urea, thimerosal, propylene glycol, chlorocresol, chloroxylenol, methyldibromoglutaronitrile/phenoxyethanol (MDBGN/PE) and benzalkonium chloride. Out of the 308 patients suspected of having contact dermatitis, 23 patients were found to have positive reactions to one or more preservatives. Preservatives that were the most frequent cause of positive reactions were thimerosal (1.6%), benzalkonium chloride (1.6%), formaldehyde (1.3%) and MDBGN/PE (0.9%). In our study, 65% of the positive reactions were caused by allergens not present in the standard series, such as thimerosal, benzalkonium chloride and MDBGN/PE. Although thimerosal caused a high rate of contact sensitivity, it may not be considered as an important allergen, because clinical relevance could not be found in any of the patients.

Proposal for a risk assessment methodology for skin sensitization based on sensitization potency data

In this paper, we propose a quantitative risk assessment methodology for skin sensitization aiming at the derivation of 'safe' exposure levels for sensitizing chemicals, used e.g., as ingredients in consumer products. Given the limited number of sensitizers tested in human sensitization tests, such as the human repeat-insult patch test (HRIPT) or the human maximization test (HMT), we used EC3 values from the local lymph node assay (LLNA) in mice because they provide the best quantitative measure of the skin sensitizing potency of a chemical. A comparison of LLNA EC3 values with HRIPT and HMT LOEL, and NOEL values was carried out and revealed that the EC3, expressed as area dose, can be used as a surrogate value for the human NOEL in risk assessment. The uncertainty/extrapolation factor approach was used to derive (a) an 'acceptable non-sensitizing area dose' (ANSAD) to protect non-allergic individuals against skin sensitization and (b) an 'acceptable non-eliciting area dose' (ANEAD) to protect allergic individuals against elicitation of allergic contact dermatitis. For ANSAD derivation, interspecies, intraspecies and time extrapolation factors are applied to the LLNA EC3. For ANEAD derivation, additional application of a variable sensitization-elicitation extrapolation factor is proposed. Values for extrapolation factors are derived and discussed, the proposed methodology is applied to the sensitizers methylchloroisothiazolinone/methylisothiazolinone, cinnamic aldehyde and nickel and results are compared to published risk assessments.

An assessment of the comparative sensitization potential of some common isothiazolinones

The isothiazolinones are known contact sensitizers. Data are presented which demonstrate that, in comparison with the chlorinated and dichlorinated compounds which share immunological cross-reactivity, the unchlorinated isothiazolinones have a lower potential for sensitization and no documented immunological cross-reaction with the chlorinated isothiazolinones.

Monitoring levels of preservative sensitivity in Europe. A 10-year overview (1991-2000)

A 10-year multicentre analysis of the frequency of sensitivity to common preservatives collected in 16 centres in 11 countries has shown stable but persisting high levels of sensitivity to formaldehyde and 5-chloro-2-methyl-4-isothiazolin-3-one + 2-methyl-4-isothiazolin-3-one (MCI/MI). It has also revealed a significant increase in the level of reactivity to methyldibromoglutaronitrile (MDBGN) from 0.7% in 1991 to 3.5% in 2000. The current high level of sensitivity to MDBGN requires an urgent safety re-evaluation and risk assessment update along with consideration of immediate lowering of use concentrations, especially in leave-on products.

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.

An update of the risk assessment for methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) with focus on rinse-off products

Methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) has been widely used during the last 20 years for the preservation of aqueous systems in cosmetics, toiletries and in various industrial applications. MCI/MI has a broad spectrum of activity against fungi and bacteria at very low concentrations. The allergic contact potential of MCI/MI has been known for many years. This paper provides a review of pre-clinical and clinical experimental studies as well as experience from dermatology clinics worldwide. This forms the basis for an update of the risk assessment for the use of MCI/MI in rinse-off products. The scientific data indicate that the actual sensitization rate observed with a contact allergen is extremely dependent on dose and type of exposure. This review of the data leads to the conclusion that, under normal use conditions, within the current permitted/ recommended use concentrations for MCI/MI of up to 15ppm, the risk of primary sensitization from the use of rinse-off products is negligible, and elicitation of allergic contact dermatitis in MCI/MI-sensitized individuals rare, after exposure to MCI/MI-preserved rinse-off products.

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.

Mutagenicity of cosmetic products containing Kathon

A variety of shampoos, conditioners, skin-care lotions, and other cosmetic products contain the biocide Kathon CG, which is a mixture of two heterocyclic isothiazolinones: methylisothiazolinone and methylchloroisothiazolinone. This mixture and the related biocide, Kathon 886, have been shown to be potent sensitizers and bacterial mutagens. Five cosmetic products that list the components of Kathon on their labels and two that do not were screened for mutagenicity with Salmonella typhimurium TA100 without S-9. Five of these products and Kathon 886 were further evaluated in TA100 without and with S-9. Kathon 886, a cosmetic product that contained Kathon, and thin layer chromatography-separated components of Kathon 886 were identified by GC/MS analysis. Three of the five products that listed Kathon were direct acting mutagens with TA100. The remaining two products were considerably more toxic than the other products and could not be evaluated for mutagenicity. The addition of S-9 reduced toxicity but did not eliminate mutagenicity. The mutagenic evaluation of Kathon 886 resulted in a dose response similar to that seen with some cosmetic products but at a 1,000-fold lower concentration, and activity was also reduced by the addition of S-9 mix. S-9 reduced activity both with and without cofactors present. Thin layer chromatography separation of the components and subsequent identification by GC/MS indicated that methylisothiazolinone was nonmutagenic while methylchloroisothiazolinone was mutagenic. Additionally, a dichlorinated compound was identified which was also mutagenic. In light of these findings and the reported skin sensitization by Kathon CG in various cosmetics, we recommend that additional testing be done to assure the safety of products containing Kathon CG.

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)

A critical commentary and updating of the guinea pig maximization test

The guinea pig maximization test (GPMT) of Magnusson and Kligman was published in 1969. Since then, a vast body of practical experience with the test has been accumulated. New information requires that certain aspects of the procedure be re-evaluated, especially with regard to the interpretation of challenge results. In particular, awareness of the phenomenon of hyperirritable skin (the 'angry back' phenomenon) suggests that presently used controls are not always adequate and may overstate allergenicity owing to false-positive reactions. The control group should be exposed to a chemical insult at induction which provokes an inflammatory reaction comparable to the test substance. We present strategies to distinguish irritant from allergic responses. Allergic reactions should persist on rechallenge weeks later, while nonspecific irritant reactions generally fade and are irreproducible in particular animals. Finally, when a chemical is identified as a contact sensitizer in the GPMT, that result is simply a categorical statement of a theoretical hazard. An assessment of risk is necessary to estimate the relevance of the test result to usage in the real world.

Occupational exposure to isothiazolinones. A study based on a product register

A national data base on chemical products (the Danish Product Register (PROBAS)) was searched in order to survey occupational exposure to isothiazolinones. 5-chloro-2-methyl-4-isothiazolin-3-one/2-methyl-4-isothiazolin+ ++-3-one(MCI/MI) was registered in 550 products, 1,2-benzisothiazolin-3-one(BIT) in 156 products and 2-n-octyl-4-isothiazolin-3-one in 16 products. For the MCI/MI-containing products, of which 343 had information on concentration, 64% of the products contained above or equal to 0.001% (10 ppm) MCI/MI. Main product categories were paints, hair shampoos, skin care products, and cleaning agents. For BIT-containing products, of which 139 had information on concentration, 54% of the products contained above or equal to 0.01% (100 ppm) BIT. Main product categories were cleaning agents, polishes, and paints. Only a few products were registered with content of 2-n-octyl-4-isothiazolin-3-one and these were not studied further. The dermatological literature has often focused on isothiazolinones in cosmetics as the source of allergy. The present study showed that attention should also be paid to occupational exposure, as isothiazolinones occur in many industrial product categories.

Results of routine patch testing of 834 patients in Turin

834 consecutive patients (630 female), aged between 26 and 46 years, who were suspected of having allergic contact dermatitis were patch tested with the GIRDCA standard series during 1989-1990. The most frequent sensitizers observed included nickel sulphate, cobalt, Kathon CG, perfumes, potassium dichromate and balsam of Peru. We have evaluated the influence of individual factors such as sex, age and occupation on the patch test results, and the coexistence of 2 or more unrelated but statistically significant sensitivities.

Allergic contact dermatitis from the preservative 1,2-benzisothiazolin-3-one (1,2-BIT; Proxel): a case report, its prevalence in those occupationally at risk and in the general dermatological population, and its relationship to allergy to its analogue Kathon CG

Occupational contact allergy to 1,2-benzisothiazolin-3-one (1,2-BIT, Proxel) is analysed. This compound is widely used in industry as a preservative in water-based solutions such as pastes, paints and cutting oils. The optimal concentration for patch testing proved to be 0.4 g/l (0.04%) in water. In 4 out of 17 patients (23%) at occupational risk (painters, paper-hangers), contact allergy to 1,2-BIT was found. Of 556 consecutive dermatological patients without clear occupational risk, 10 (1.8%) showed positive patch tests to 1,2-BIT; in 3 patients 1,2-BIT contact allergy was related to domestic paper-hanging. Although the chemical structure of 1,2-BIT shows some analogy with the preservative Kathon CG, true cross-sensitivity was found to be unlikely.

Isothiazolinones (MCI/MI): 200 ppm versus 100 ppm in the standard series

In an attempt to define the optimal test concentration for isothiazolinones, 200 and 100 ppm of 5-chloro-2-methyl-4-isothiazolin-3-one/2-methyl-4- isothiazolin-3-one (MCI/MI) in aq. solution were tested simultaneously in 918 consecutive eczema patients. 3.4% were positive to 200 ppm and 1.7% to 100 ppm, indicating that up to 50% of the cases might have been missed. Among the 33 cases with positive reactions, 21 showed stronger reactions to 200 than to 100 ppm, while 9 had reactions of the same strength. Use tests were carried out in 7 cases, of which 2 were positive. MCI/MI remains a peculiar allergen and some of the problematic factors are: the morphology of the test reactions, the difficulties in tracking down the exposure (past or current relevance), the multisensitivity (MCI/MI plus other allergens), the outcome of the use tests and the optimal test concentration. Our present strategy is to use 200 ppm as an indicator and then to carry out serial dilution and use tests in each "positive" case.

Contact sensitization to 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one (MCI/MI). A European multicentre study

The frequency of positive reactions to 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one (MCI/MI) were studied at 22 European contact dermatitis clinics over a period of 1 year. A total of 4713 patients participated. All the patients were patch tested with nickel sulphate, formaldehyde, paraben-mix, and MCI/MI. 19.4% of the patients had positive patch tests to nickel, making this the most common allergen. 3% of the patients reacted to 100 ppm MCI/MI, while 2.6% reacted to formaldehyde and 1.1% to parabens. There was great variation in the frequency of MCI/MI sensitivity among the 22 centres. MCI/MI contact allergy was most common among women and in patients with facial dermatitis, while it was rarely seen in patients with dermatitis on the lower legs. There were no fluctuations in the number of positive patch tests to MCI/MI on a monthly basis when the results from all centres were combined. 117 of the 141 MCI/MI sensitized patients included in the study were retested. 88% had positive patch tests when retested. 101 of the MCI/MI-sensitive patients participated in a double-blind, placebo-controlled product use test. This test showed that 31% of the MCI/MI-sensitive patients had a positive reaction to a MCI/MI-preserved product. Only a few patients reacted to a control product. It is concluded that the preservative MCI/MI is an important new contact allergen.

Methylchloroisothiazolinone-methylisothiazolinone reactions in patients screened for vehicle and preservative hypersensitivity

More than 1100 patients were tested with methylchloroisothiazolinone-methylisothiazolinone, 100 ppm, in aqueous and petrolatum-based patch test materials from 1985 to 1987 by members of the North American Contact Dermatitis Group. Thirteen reactions to the aqueous materials and 10 to the petrolatum-based materials were observed. Irritant reactions were infrequent, and about half the reactions were deemed relevant. From 1984 to 1985, patch tests with this substance at a concentration of 250 ppm in petrolatum were conducted. Thirteen persons were identified as allergic, but three others were sensitized by the patch test procedure. Sensitization as not observed in tests with aqueous or petrolatum-based substance at a concentration of 100 ppm, and this concentration appears to be the best compromise between safety and sensitive detection of allergy. Use tests are helpful but not infallible as a guide in establishing relevance with methylchloroisothiazolinone-methylisothiazolinone. Wash-off products are frequently well tolerated by patients with positive reactions to this substance.

Patch test sensitivity to the preservative Kathon CG in Spain

Kathon CG is a very well studied preservative used in cosmetics and toiletries. It is effective in low concentrations (3 to 15 ppm active ingredients) and exhibits outstanding antimicrobial activity against gram-negative and gram-positive bacteria, yeasts and fungi. Although this biocide is not considered to pose a toxicological hazard at recommended use levels, the sensitizing potential of Kathon CG has been established. From November 1988 to June 1989, we patch tested 626 unselected contact dermatitis patients with Kathon CG solution containing 200 ppm active ingredients and obtained 22 (3.5%) positive reactions. Relevance was established in 7 of the 22 patients. Women were predominantly sensitized, the principal source of sensitization being cosmetics.

Kathon CG and cosmetic products

Kathon CG was determined in 156 of the most commonly used cosmetic products in Denmark. 42% of the cosmetic products were found to contain Kathon CG. Kathon CG was present in 48% of "rinse off" and 31% of "leave on" cosmetic products. The 3:1 ratio of chloromethyl isothiazolinone (CMI): methyl isothiazolinone (MI) in Kathon CG was found to be disturbed in 41% of Kathon CG preserved cosmetic products. The disturbed CMI/MI ratio was shown in 29% "rinse off" and 73% "leave on" cosmetic products. It is suggested that the chemical reaction of the ketone group of the isothizaolinones with other ingredients in cosmetic products may disturb the CMI/MI ratio of Kathon CG. The results of the study have been discussed in relation to the use of Kathon CG in cosmetic products as well as test material for allergic reaction.

Panels of allergens for specific occupations

It is important to have available panels of materials for patch testing patients working in specific occupations. Although it is not essential in every case to test with each substance listed on a given panel, careful consideration of the patient's work environment should suggest the specific test items that will provide the highest diagnostic yield in cases of allergic contact dermatitis.

Isothiazolinone preservative: cause of a continuing epidemic of cosmetic dermatitis

A preservative system for cosmetics and toiletries containing as active ingredients a mixture of methylisothiazolinone and methylchloroisothiazolinone (1.5%) is an important cause of cosmetic allergy in many European countries. Most cases have been caused by products of the "leave-on" variety, such as moisturising creams. The use of isothiazolinone preservative in such products should be abandoned. More critical evaluation of its sensitising potential before marketing might have prevented the continuing epidemic of allergic cosmetic dermatitis due to this preservative. New chemicals should undergo extensive toxicological evaluation before their use in cosmetics is allowed. Ingredient labelling should be made a legal requirement.

Sensitization to Kathon CG in Geneva and Switzerland

Between October 1986 and June 1987 we patch tested 420 patients with Kathon CG at 100 ppm and obtained 23 positive reactions (5.5%). The other 5 Swiss university clinics joined our study between January and June 1987 and obtained sensitization rates ranging from 0.7 to 7.5%. The total mean value including Geneva was 3.6%. We did threshold patch testing in 12 patients with the following Kathon CG dilutions: 100, 50, 25, 15 and 7 ppm. We observed progressively diminishing skin reactions, especially below 25 ppm, but we still obtained slight positive reactions in 2 patients with Kathon CG at 7 ppm. Those reactions were relevant because the dermatitis disappeared when the use of Kathon-containing creams was discontinued.

Sensitivity to Kathon CG: findings in 365 consecutive patients

In the period from 1983 through 1986, 365 consecutive patients suspected as having allergic contact dermatitis were tested for reaction to Kathon CG. This test was positive in 20 of these patients: irritant responses in 7 and allergic sensitivity in 13. Provocative use testing was positive in 1 of the 3 allergic patients tested. The characteristics of this group of patients include having a mean age older than that of the general population or of our population of dermatologic patients, having histories of long-standing dermatitis, and reporting exposure to various leave-on formulations. Our rate of positive tests, 3.6%, is similar to that reported by other investigators, although sensitivity testing results differ from center to center. It is recommended that, in certain clinical situations, caution be exercised in the unsupervised use of leave-on products containing Kathon CG.

Kathon CG reactivity in 1396 consecutively patch tested patients in the Copenhagen area

In 1396 consecutively patch tested patients 18 (1.3%) reacted to Kathon CG. Relevance was established in 4 of the 18 patients. The frequency of positive reactions to Kathon CG in eczema patients seems to have been stable in Denmark during the period 1983 to 1988.

Frequency of sensitisation to the preservative Kathon CG

The incidences of sensitisation to Kathon CG are reported for patients routinely tested from 1984 to 1986 in Bari, London, Louvain, Nijmegen, Oulu and San Francisco. For these 3 years, the overall frequency of sensitisation varied for women from 3.3% in Oulu to 0.6% in London and San Francisco and for men from 1.4% in Oulu to 0% in San Francisco. Women were predominantly sensitised, probably by cosmetics, toiletries and domestic cleaners. Occupational sensitisation was much less frequent.