Skin elicitation threshold of ethylbutyl thiourea and mercaptobenzothiazole with relative leaching from sensitizing products

Assessment of Contact Allergens in "Hypoallergenic" Athletic Shoes by Mass Spectrometry

Background: Identification of athletic shoes for patients with contact allergy is difficult. Company reports of allergen content are often incorrect. Objectives: To determine whether chemical analysis of 4 athletic shoes, previously reported to be free of the most common contact allergens, contain quantifiable allergen levels. Methods: Samples from the uppers and insoles of 4 shoes believed to be free of common allergens were assessed by mass spectrometry. A total of 4 rubber accelerators and 2 adhesives were directly quantified and additional 7 rubber accelerators were assessed using semiquantitative measures. Results: Aside from carbamates (assayed as 59 ppm zinc in insoles) in SeaVee's Sixty-Six sneakers, para-tertiarybutylphenol formaldehyde resin (PTBFR) (assayed as 7.6 ppm paratertiary butylphenol or 4-tertiary butylphenol [4TBP] in uppers) in Allbirds Tree Runners and rosin (assayed as 628 ppm sodium abietate in uppers) and carbamates (24 ppm zinc in uppers) in Saucony Jazz sneakers, these shoes had low levels of all allergens assayed in this study. Tom's Carlo sneakers contained rosin (127 ppm sodium abietate in insoles), PTBFR (6.5 ppm 4TBP in uppers), and carbamates (112 ppm sodium abietate in insoles) but had low levels of all other assayed allergens. Conclusions: Although identifying allergen-free shoes is challenging, the results of this analysis will help patch testing physicians recommend athletic shoes to patients with specific allergies.

Patch Testing of Mercaptobenzothiazole and Mercapto Mix: The North American Contact Dermatitis Group Experience, 1994-2016

OBJECTIVES

Mercapto compounds are a category of rubber accelerators that may cause allergic contact dermatitis. This study characterizes patch test reactions to mercaptobenzothiazole (MBT) and mercapto mix (MM) in a large North American population.

METHODS

The 1994-2016 North American Contact Dermatitis Group screening series data were analyzed. Patients with allergic reactions to either MBT or MM (mercapto+) were included. The following characteristics were analyzed: strength of reaction, clinical and occupational relevance, coreactivity with other rubber accelerators, and sources of exposure.

RESULTS

A total of 49,795 patients were tested to mercapto compounds from 1994 to 2016; 633 (1.3%) had positive reactions to MBT and/or MM. The frequency to both MBT and MM significantly decreased over time (P < 0.0001). Mercapto+ patients were significantly more likely to be male, have occupationally related skin disease, and report involvement of the hands and/or feet (P < 0.0001). They were significantly less likely to have face, scalp/ears/neck, or trunk involvement (P ≤ 0.0001). There was significant coreactivity with carba mix (23.4%) and thiuram mix (32.5%). Mercaptobenzothiazole and MM reactions were frequently clinically (81.7% and 83.5%, respectively) and occupationally relevant (29.8% and 33.4%, respectively). Gloves were the most common source (31.3% and 30.9%, respectively).

CONCLUSIONS

Patch test positivity to mercapto compounds significantly decreased from 1994 to 2016 but remains clinically and occupationally relevant.

Making Glove Decision Less of a White Knuckling Experience: A Systematic Review and Inventory of Glove Accelerator Contents

Background

Accelerators in medical gloves are a common cause of allergic contact dermatitis among healthcare workers.

Objective

A systematic review of medical and nursing literature, patch testing reports, and chemical analyses of gloves was conducted to assess accelerator contents reported in the literature and to identify accelerator-free gloves.

Methods

A systematic literature search was performed in OVID Medline and OVID EMBASE. Hand-searching of reference lists of articles in the field and author input generated the remainder of articles assessed.

Results

We present an inventory of accelerator contents of gloves and accelerator-free glove options as reported in the literature as a clinical reference tool to assist allergen-free glove selection for individuals suffering from allergic contact dermatitis due to rubber accelerators.

Limitations

Pertinent limitations of our review include lack of predefined study exclusion criteria and screening of the studies identified in the search by 1 review author only.

Conclusion

The glove inventory we provide summarizes the available literature regarding medical and surgical glove accelerator content, describing gloves both by brand and manufacturer as well as by accelerators.

Glove-Related Allergic Contact Dermatitis

Hand dermatitis is a common condition with a lifetime prevalence of 20%. Glove allergic contact dermatitis (ACD) is a very important dermatitis affecting health care workers, hairdressers, cleaning personnel, kitchen workers, craftsmen, construction workers, laboratory workers, and homemakers. Occupationally related cases may be severe and can result in significant disability. Glove ACD is most commonly due to exposure to rubber accelerators, which are compounds that are added to rubber during production to increase strength and durability. Given the known allergic potential of these compounds, glove manufacturing companies have reformulated gloves leading to the introduction of new rubber allergens. In this review, we will discuss risk factors for glove ACD, both common and uncommon allergens in gloves, common contact allergens that permeate gloves, and patch testing to help uncover the inciting allergen(s).

Dose-Response Relationships and Threshold Levels in Skin and Respiratory Allergy

A literature study was performed to evaluate dose-response relationships and no-effect levels for sensitization and elicitation in skin- and respiratory allergy. With respect to the skin, dose-response relationships and no-effect levels were found for both intradermal and topical induction, as well as for intradermal and topical elicitation of allergenic responses in epidemiological, clinical, and animal studies. Skin damage or irritation may result in a significant reduction of the no-effect level for a specific compound. With respect to the respiratory tract, dose-response relationships and no-effect levels for induction were found in several human as well as animal studies. Although dose-response relationships for elicitation were found in some epidemiological studies, concentration-response relationships were present only in a limited number of animal studies. Reported results suggest that especially relatively high peak concentrations can induce sensitization, and that prevention of such concentrations will prevent workers from developing respiratory allergy. Moreover, induction of skin sensitization may result in subsequent heightened respiratory responsiveness following inhalation exposure. The threshold concentration for the elicitation of allergic airway reactions in sensitized subjects is generally lower than the threshold to induce sensitization. Therefore, it is important to consider the low threshold levels for elicitation for recommendation of health-based occupational exposure limits, and to avoid high peak concentrations. Notwithstanding the observation of dose-response relationships and no-effect levels, due to a number of uncertainties, no definite conclusions can be drawn about absolute threshold values for allergens with respect to sensitization of and elicitation reactions in the skin and respiratory tract. Most predictive tests are generally meant to detect the potential of a chemical to induce skin and/or respiratory allergy at relatively high doses. Consequently, these tests do not provide information of dose-response relationships at lower doses such as found in, for example, occupational situations. In addition, the observed dose-response relationships and threshold values have been obtained by a wide variety of test methods using different techniques, such as intradermal exposure versus topical or inhalation exposure at the workplace, or using different endpoints, which all appear important for the outcome of the test. Therefore, especially with regard to respiratory allergy, standardized and validated dose-response test methods are urgently required in order to be able to recommend safe exposure levels for allergens at the workplace.

Dissolution of materials in artificial skin surface film liquids

The dissolution of chemical constituents from jewelry, textiles, cosmetics, drugs, industrial chemicals, and particles in direct and prolonged contact with human skin is often assessed in vitro using artificial skin surface film liquids (SSFL). To provide meaningful results, the composition of artificial SSFL should accurately mimic human sweat and sebum, and the conditions of the in vitro test system should accurately reflect in vivo skin conditions. We summarized the reported composition of human SSFL and compared it to 45 different formulations of artificial sweat and 18 formulations of artificial sebum (studies published from 1940 to 2005). Conditions of in vitro dissolution test systems were reviewed and compared to in vivo skin conditions. The concentrations of individual constituents and pH of artificial sweat and concentrations of artificial sebum constituents are not always within ranges reported for human SSFL. Nearly all artificial SSFL lack many of the constituents in human SSFL. To develop a comprehensive model SSFL, we propose a standard SSFL, modified from the two best published sweat and sebum formulations. Little is known concerning the influence of test system conditions on dissolution, including SSFL temperature, container material composition, agitation, and physicochemical properties of the test article on dissolution. Thus, both a need and an opportunity exist for standardizing the composition of artificial SSFL and in vitro dissolution test methodologies. To standardize in vitro dissolution test systems, we recommend: maintaining artificial SSFL at a biologically relevant temperature appropriate to the human activity being modeled, carefully selecting test and sample storage containers to avoid bias in dissolution measurements, accounting for friction between a test article and skin in a biologically plausible manner, and physicochemical characterization of the test article or material to better understand mechanisms of dissolution and potential mechanisms of toxic action of dissolved material. More accurate modeling and better understanding of chemical dissolution from articles in contact with the skin will ultimately improve risk decision making, thereby protecting even the most susceptible persons from adverse health effects resulting from skin exposure.

Survey of sulfur-containing rubber accelerator levels in latex and nitrile exam gloves

2-Mercaptobenzothiazole and zinc dialkyldithiocarbamates are commonly used sulfur-containing rubber vulcanization accelerators known to cause allergic contact dermatitis. Exposure to these agents occurs through clothing such as undergarments and shoes, latex medical devices and latex and nitrile gloves. A simple, inexpensive screening method for total sulfur accelerator and a high performance liquid chromatographic speciation method were developed in the present study. These methods were applied to screen and quantify the sulfur accelerator content from 38 brands of 'off-the-shelf' latex and nitrile gloves obtained from commercial vendors. It was found that accelerator levels ranged from not detectable to 7.35 mg/g in the gloves analysed. Brands were found to contain single and multiple accelerator species within the glove. Powdered gloves had significantly higher accelerator levels than powder-free gloves from the same manufacturer; however, these chemical accelerators do not preferentially partition to the powder. The present analytical methodology is suitable for both manufacturing quality validation purposes, as well as for accelerator allergy research.

HPLC analysis of alkyl thioureas in an orthopaedic brace and patch testing with pure ethylbutylthiourea

Ethylbutylthiourea (EBTU) is an accelerator used in the production of chloroprene (neoprene) rubber. EBTU occurs in a mixture with diethylthiourea (DETU) and dibutylthiourea (DBTU) in the accelerator. An analytical method originally developed for analysis of zinc dithiocarbamates in rubber has been used to analyse EBTU, DETU and DBTU in a knee brace responsible for an allergic contact dermatitis in a gardener suffering from arthrosis. EBTU was isolated and gave positive reactions when tested as a pure compound. The test reaction was accompanied by positive reactions to DETU and DBTU.

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.

Thresholds in contact sensitization: immunologic mechanisms and experimental evidence in humans--an overview

The evidence from practical experience in man, from controlled human testing and from both chemical and biological mechanistic considerations, demonstrates that the thresholds for skin sensitization exist both at the level of induction as well as sensitization. For a given contact allergen, the concentration (expressed in dose per unit area), which is at the threshold, has to be defined in terms of the nature and extent of the skin contact involved, and whether it is the induction of skin sensitization or its elicitation that is involved, since the numerical values will depend heavily on these parameters. The induction and elicitation of contact allergy is influenced by several factors: the total dose of the allergen, its surface concentration, the size of area over which it is applied, antigenic potency of the substance, number of exposures, anatomical site of exposure, effect of draining lymph nodes, matrix (vehicle) of allergen, effect of occlusion, degree of percutaneous penetration, effect of diseased skin/trauma and possibly a host of other, as yet unknown, variables.

Allergic contact dermatitis elicitation thresholds of potent allergens in humans

Literature scoured for human allergenicity to individual chemicals yields a limited number of potent sensitizers, which can be classified in four categories: metals, botanicals, biocides and miscellany. Potency is defined as strong for substances eliciting eczematous reactions to patch concentrations of 500 ppm (parts per million) or less in sensitized individuals. Most data encountered stem from studies conducted on dermatology patients tested routinely for hypersensitivity; only few data have been generated by systematic serial dilution testing.

Skin sensitization thresholds: determination in predictive models

For many years, test methods for the prospective identification of skin sensitizing chemicals have been widely available. However, although these techniques have permitted the identification of the great majority of skin sensitizers, their use in assessing the relative potency of a particular chemical as a human contact allergen has not been well described. A primary reason for this is the inherent difficulty of such an exercise. A complex phenomenon involving interactions between the vehicle, the allergen, the skin and its inflammatory responses takes place during the induction and elicitation of sensitization. All these factors can have a profound effect on the threshold values determined for a skin sensitizer. Consequently, whether the assessment is conducted in humans or in animal models, a threshold concentration is always a function of the method of measurement as much as the potency of the allergen. Although an exhaustive review has not been carried out, this paper considers the attempts that have been made to assess relative potency by the measurement of dose-response relationships and the determination of induction and elicitation thresholds in both animal models and in humans. The latter has special relevance for regulatory toxicology and this matter is given particular attention in this article. Finally, recommendations are made: (a) that threshold concentrations for skin sensitizers should be determined on a case by case basis in relation to the likely mode of skin contact; (b) where the data are used in comparisons of skin sensitization potency, then there should be standardization of the method used for the determinations.