Thiuram allergy--a potential dermal allergy among health care workers

Occupational health nurses should be cognizant of the myriad exposures that can result in dermal reactions among health care workers.

Patch testing discordance alert: false-negative findings with rubber additives and fragrances

From July 1996 through June 1998, the North American Contact Dermatitis Group evaluated 318 patients for suspected contact dermatitis by patch testing simultaneously with Finn Chambers and the T.R.U.E. Test allergen system. Discrepancies between the two systems were found in some of the results, particularly with fragrance and rubber allergens. These results suggest that positive reactions to fragrance, thiuram, and carba mix allergens may be missed if the T.R.U.E. Test is used alone.

Development of an immunoassay (ELISA) for the quantification of thiram in lettuce

Two competitive immunoassays, a laboratory assay based on microwell plates and a field test based on the use of polystyrene tubes, have been developed for the quantification of thiram in lettuces. Concerning the laboratory assay, the calibration curve for thiram had a linear range of 11 to 90 ng/mL and a detection limit of 5 ng/mL. Precision of the assay presented coefficient of variation values <9% and the recovery of thiram from lettuce averaged 89% across the range of the immunoassay method using 30 min extraction with water/acetone (50:50, v/v). The tube-based method was developed in order that an extract of lettuce, containing thiram at the MRL (8 ppm), would be found on the linear part of the standard curve. The calibration curve for thiram has a linear range of 100 to 800 ng/mL (1.39 to 11.1 ppm in lettuce) and a detection limit of 40 ng/mL.

A quantitative method for assessing the sensitizing potency of low molecular weight chemicals using a local lymph node assay: employment of a regression method that includes determination of the uncertainty margins

Risk assessment of sensitizing chemicals requires, besides hazard identification, the assessment of potency. To examine the sensitizing capacity of low molecular weight chemicals, a murine local lymph node assay (LLNA) was used. The sensitizing capacity of known allergens was quantified by dose-response modeling. At a stimulatory index (SI) of 3, the corresponding estimated concentration was calculated (EC(3)), together with a confidence interval to take account of the quality of the particular data set. We tested ten allergens (ethyl-p-aminobenzoate (benzocaine), diethylamine (DEA), 2,4-dinitrochlorobenzene (DNCB), 2-mercaptobenzothiazole (MBT), 4-ethoxymethylene 2-phenyl oxazol-5-one (oxazolone), phthalic anhydride (PA), toluene diisocyanate (TDI), trimellitic anhydride (TMA), tetramethylthiuramdisulfide (TMTD) and zincdimethyldithiocarbamate (ZDMC)). Oxazolone showed the strongest sensitizing potency followed in this order by DNCB, TDI, TMA, PA, TMTD, ZDMC, MBT, benzocaine and DEA. The approach performed in this study is a way to accurately assess the potency of sensitizing chemicals and thus a possibility for classification.

Contact sensitivity to chromate: comparison at a London contact dermatitis clinic over a 10-year period

It has been argued that for chromate sensitivity to be reduced, then ferrous sulfate should be added to cement. This has not yet been done in the UK. To explore this further, we have looked at the comparative sensitization rates of patients attending the St. John's Institute of Dermatology Contact Dermatitis Clinic between the years 1982-3 and 1992-3. Patch-test-positive rates for females were not significantly different between the 2 populations studied (1982-3, 1.59% and 1992-3, 1.99% p NS). Similarly, there was no significantly different rate between the males (1982-3, 3.99% and 1992-3, 4.25% p NS) in the same time period. There was no difference in the distribution of eczema in chromate-positive subjects, nor of cobalt co-sensitization, a crude indicator of sensitization via cement. This work demonstrates no appreciable difference in the frequency of chromate sensitivity between the early 1980s and 1990s in London. Adding ferrous sulfate to cement may help to lower the frequency in the future.

Contact allergy and exposure patterns to thiurams and carbamates in consecutive patients

Sensitization to rubber is most often due to sensitization to thiurams. Positive patch test reactions to carbamates are less frequent, and usually only diagnosed in patients with positive patch test reactions to thiurams as well. The aim of the present study was to describe the relative frequency of sensitization to thiuram mix (TH mix) and zinc diethyldithiocarbamate (ZDC) in a population where the exposure to these chemicals from rubber gloves was previously studied and considered to be of approximately the same order of magnitude. The thiuram derivatives seemed to be the most important sensitized (frequency 2.8%) compared to ZDC (frequency 0.5%), which has been the most frequently reported sensitizer among the carbamates in rubber gloves. An interesting observation was that the probability that the patient was reacting to ZDC was strongly associated with the strength of the patch test reaction to TH mix. This observation may add a new aspect to the discussion about cross-reactivity versus concomitant sensitization of thiurams and carbamates.

Evaluation of contact sensitivity of rubber chemicals using the murine local lymph node assay

The sensitizing abilities of 4 rubber additives, tetramethylthiuram disulfide (TMTD). 2-mercaptobenzothiazole (MBT), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD) and zinc diethyldithiocarbamate (ZDEC), were evaluated using the murine local lymph node assay. Exposure to IPPD induced a significant increase of lymph node cell proliferation in the draining lymph nodes even at a low concentration. Exposure to TMTD and MBT induced moderate proliferative responses, while ZDEC induced a weak proliferation even at the higher concentrations. The sensitizing potency of each chemical was described in terms of the concentration that increased lymph node cell proliferation by a factor of 2 over that in the vehicle-treated control group. The concentrations of IPPD, TMTD, MBT and ZDEC were 0.14%, 0.35%, 4.2% and > 10%, respectively.

Release of thiurams and carbamates from rubber gloves

A method for quantitative determination of thiuram and carbamate derivatives released from rubber gloves into synthetic sweat is presented. The analysis was based upon determination of ester derivatives using gas-chromatography/mass spectrometry and isotope-dilution. The detection limit was 0.1 mg thiuram/carbamate in 200 ml synthetic sweat (0.5 ppm). The release of thiurams and carbamates from 5 household and 5 surgical types of gloves into synthetic sweat was determined. Each of the natural rubber gloves released varying amounts of thiurams (0-4.3 mg) as well as carbamates (0-8.1 mg). 22 thiuram-sensitized patients were patch tested with pieces of the gloves. Gloves releasing considerable amounts of thiurams and/or carbamates seemed to cause more positive patch test reactions in these patients than gloves releasing smaller amounts. Surgical gloves made from natural rubber caused a substantial larger number of positive patch test reactions than household gloves made from natural rubber. The amounts released per cm2 of the gloves were of the same order of magnitude as the content per cm2 patch test of thiuram mix, diluted 1:10. The accessibility of a quantitative, chemical analysis for thiurams and carbamates released from rubber gloves makes it reasonable to ask for declarations of rubber gloves. Proposals for threshold values for release of thiurams and carbamates from rubber gloves may be given in the future.

The problem of the sensitization to dithiocarbamates in thiuram-allergic patients

Because of the occurrence of hand dermatitis in members of a surgical staff due to allergy to thiuram-containing rubber gloves, an investigation was performed about cross-sensitization between thiuram compounds and dithiocarbamates. Positive reactions to dithiocarbamates were compared with reactions to 8 brands of hypo-allergenic or dithiocarbamate-containing surgical gloves. There appeared to be a marked difference in reactions to the dithiocarbamate-containing gloves. Some brands gave negative or nearly always negative reactions, while other brands caused many positive reactions. Thiuram-allergic patients were advised to wear nonreacting rubber gloves or PVC gloves.

Contact allergy: predictive testing in man

Predictive tests are of value in forecasting the response of a population to a sensitizer; diagnostic testing is used to determine what substances may actually be producing dermatologic problems. Skin sensitization predictive and diagnostic data for the eleven most frequently encountered skin sensitizers in Western Europe, Canada and the United States are reviewed. These compounds include two drugs (benzocaine and neomycin), two cosmetic ingredients (p-phenylenediamine and balsam of Peru), four preservatives (formaldehyde, ethylenediamine, parabens and mercurials) and three ingredients of wearing apparel (nickel, chromium and thiram). Many of the data were collected by the North American Contact Dermatitis Group and the International Contact Dermatitis Research Group on tests with 1,200 and 4,825 dermatologic patients, respectively; the remainder were obtained by individual investigators with smaller groups of subjects. The data obtained by various investigators are discussed in relation to the factors which affect the extent and degree of sensitization which they can cause.