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Patch-test reactions to thioureas are frequently relevant
Nneka I Comfere1, Mark D P Davis, Debra D Fett
1Department of Dermatology, Mayo Clinic, Rochester, MN, USA.
Dermatitis : Contact, Atopic, Occupational, Drug
|October 26, 2005
Summary
Allergic contact dermatitis from thioureas is common and clinically relevant. Standard patch testing should include mixed dialkyl thioureas to identify exposures in various settings.
Area of Science:
- Dermatology
- Allergology
- Occupational Health
Background:
- Thioureas are industrial chemicals used as antioxidants in rubber and fixatives in photography.
- Reported cases of thiourea-induced allergic contact dermatitis are infrequent.
- Standard patch test series often omit thiourea allergens, despite their industrial use.
Purpose of the Study:
- To investigate the prevalence and clinical significance of patch test reactions to thioureas.
- To assess the diagnostic utility of thiourea testing in patients with suspected contact dermatitis.
Main Methods:
- Retrospective analysis of patch test data from 1,368 patients (January 1999 - June 2001).
- Patients underwent standard screening allergen series and patch testing.
- The institution's series included 1% mixed dialkyl thioureas in petrolatum.
Main Results:
- 2.4% (33/1,368) of patients exhibited patch test reactions to mixed dialkyl thioureas.
- 42% (14/33) of positive reactions were deemed clinically relevant.
- Positive reactions indicate confirmed thiourea exposure in diverse occupational and consumer settings.
Conclusions:
- Patch test reactions to thioureas are as frequent as many other standard allergens.
- Thiourea reactions frequently demonstrate clinical relevance, highlighting occupational and consumer exposure.
- Inclusion of mixed dialkyl thioureas in standard patch test screening series is recommended.