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Investigation of diethylthiourea and ethyl isothiocyanate as potent skin allergens in chloroprene rubber
Stockholm University, Faculty of Science, Department of Analytical Chemistry.
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2015 (English)In: Contact Dermatitis, ISSN 0105-1873, E-ISSN 1600-0536, Vol. 72, no 3, p. 139-146Article in journal (Refereed) Published
Abstract [en]

Background

Exposure to chloroprene rubber has resulted in numerous cases of allergic contact dermatitis, attributed to organic thiourea compounds used as vulcanization accelerators. However, thiourea compounds are not considered to be strong haptens.

Objectives

To analyse common commercial chloroprene materials for their contents of diethylthiourea (DETU), dibutylthiourea (DBTU), diphenylthiourea (DPTU), and their degradation products, isothiocyanates; and to investigate the sensitization potencies of possible degradation products of the mentioned thiourea compounds.

Methods

Liquid chromatography/mass spectrometry (MS) was used for quantification of organic thiourea compounds in chloroprene products, such as medical, sports and diving gear; isothiocyanates were measured by solid-phase microextraction/gas chromatography/MS. Sensitization potencies were determined with the murine local lymph node assay (LLNA).

Results

DETU was identified at concentrations of 2.7-9.4 mu g/cm(2) in all samples, whereas neither DBTU nor DPTU was detected. At 37 degrees C, degradation of DETU in the materials to ethyl isothiocyanate (EITC) was detected. EITC and ethyl isocyanate showed extreme and strong sensitization potencies, respectively, in the LLNA.

Conclusions

DETU can act as a prehapten, being degraded to EITC when subjected to body temperature upon skin contact. EITC could thus be the culprit behind allergic contact dermatitis caused by chloroprene rubber.

Place, publisher, year, edition, pages
2015. Vol. 72, no 3, p. 139-146
Keyword [en]
chloroprene, contact dermatitis, diethylthiourea, ethyl isothiocyanate, exposure analysis, local lymph node assay, neoprene, rubber chemicals
National Category
Dermatology and Venereal Diseases Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
URN: urn:nbn:se:su:diva-116000DOI: 10.1111/cod.12318ISI: 000349965800002PubMedID: 25532938OAI: oai:DiVA.org:su-116000DiVA, id: diva2:801877
Note

AuthorCount:5;

Available from: 2015-04-10 Created: 2015-04-08 Last updated: 2018-02-12Bibliographically approved
In thesis
1. Analytical methodologies for common skin allergens: Organic thioureas, isothiocyanates and fragrance hydroperoxides in everyday life products
Open this publication in new window or tab >>Analytical methodologies for common skin allergens: Organic thioureas, isothiocyanates and fragrance hydroperoxides in everyday life products
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes analytical methodologies for the determination of important skin-sensitizing chemicals in two types of commercial items: chloroprene rubber and fragrance products which are both well-known to be associated with contact allergy.

Chloroprene rubber (neoprene) is widely used in different applications and products, such as bags, gloves, wetsuits, braces, mouse pads et c. Exposure to chloroprene rubber materials has resulted in numerous cases of allergic contact dermatitis. Organic thioureas have been considered the main culprits, even though they at the same time have been classified as weak or non-sensitizers in the murine local lymph node assay (LLNA). Previous findings indicate that a possible reason for sensitization is that organic thioureas are being metabolized in the skin into more reactive electrophiles, such as isothiocyanates and isocyanates, after skin exposure. In this thesis, chemical analyses of a number of chloroprene products from the European open market showed the presence of diethylthiourea in all analyzed items, while other organic thioureas could not be detected. The levels of diethylthiourea varied, with the highest at 158 µg cm-2 in a used back support that had previously caused allergic contact dermatitis in a patient. Furthermore, it was discovered that all the examined items emitted ethyl isothiocyanate. LLNA showed that ethyl isothiocyanate is a strong skin sensitizer, as has been shown earlier for other tested isothiocyanates. Isothiocyanates were shown to be thermally formed from diethyl, diphenyl and dibutylthiourea at a temperature as low as 35 °C, i. e. around skin temperature. Altogether, the results from these experiments, patch tests and chemical analyses revealed that isothiocyanates are important haptens in contact allergy to chloroprene rubber.

Fragrances constitute one of the main causes of contact allergy, next to nickel and preservatives. The most widespread fragrances in cosmetics and perfumes on the market are monoterpenes, such as linalool and limonene, which at air exposure easily oxidize to hydroperoxides, which are strongly skin sensitizing compounds and the main haptens. Despite this, there is so far no EU regulation concerning fragrance hydroperoxides in products, which may be due to lack of analytical methods which can reliably measure them in fragrances. Presented in this thesis is a toolbox of different analytical methods, applied on essential oils, shampoo, patch test preparations and different types of perfumes. Furthermore, one of our studies elucidated the first case (to my knowledge) of allergic contact dermatitis as being correlated to a product that contains a fragrance hydroperoxide.

Taken together, the thesis shows the importance of developing analytical methods for the identification, measurement and detection of important haptens in contact allergy. 

Place, publisher, year, edition, pages
Stockholm: Department of Environmental Science and Analytical Chemistry, Stockholm University, 2018. p. 79
Keyword
Chemical analysis, contact allergy, chloroprene rubber, diethyl thiourea, ethyl isothiocyanate, fragrance hydroperoxides
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-152640 (URN)978-91-7797-149-8 (ISBN)978-91-7797-150-4 (ISBN)
Public defence
2018-03-22, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
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Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 5: Manuscript.

Available from: 2018-02-27 Created: 2018-02-05 Last updated: 2018-02-27Bibliographically approved

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