Positive patch-test reactions to mixed dialkyl thioureas: cross-sectional data from the North American Contact Dermatitis Group, 1994 to 2004.
BACKGROUND
Allergic contact dermatitis from thioureas is uncommon but may result from exposure to rubber, especially neoprene.


OBJECTIVE
To (1) describe the population with positive patch-test reactions to mixed dialkyl thioureas (MDTU) (ie, diethylthiourea and dibutylthiourea); (2) determine clinical and occupational relevance associated with reactions to MDTU and identify the most commonly related sources and occupations; and (3) examine the frequency of co-reacting allergens in MDTU-positive patients.


METHODS
A retrospective analysis of cross-sectional data of 22,025 patients patch-tested by the North American Contact Dermatitis Group between 1994 and 2004.


RESULTS
Of 21,898 patients tested with MDTU, 225 (1.0%) had positive reactions; of these, 173 (76.9%) were currently relevant and 29 (17.1%) were occupationally relevant. Patients positive to MDTU were 2.6 times more likely to have foot involvement than patients with positive reactions to other allergens (p < .0001). Footwear was the most commonly identified source overall (20.0%) whereas gloves were the most common occupational source. Of the 173 patients with currently relevant MDTU reactions, 24.9% also reacted to another rubber allergen.


CONCLUSIONS
Current clinical relevance of reactions to MDTU was high; occupational relevance was less frequent. Patch tests with common rubber allergens (carbamates, thiurams, and mercaptobenzothiazole) may fail to detect many cases of thiourea-induced rubber allergic contact dermatitis.
Warshaw
Erin M
EM
Cook
Jeremy W
JW
Belsito
Donald V
DV
DeLeo
Vincent A
VA
Fowler
Joseph F
JF
Maibach
Howard I
HI
Marks
James G
JG
Mathias
C G Toby
CG
Pratt
Melanie D
MD
Rietschel
Robert L
RL
Sasseville
Denis
D
Storrs
Frances J
FJ
Taylor
James S
JS
Zug
Kathryn A
KA
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000485:Allergens / Q000009:adverse effects; D002648:Child; D002675:Child, Preschool; D003020:Clothing / Q000009:adverse effects; D003430:Cross-Sectional Studies; D019992:Databases as Topic; D017449:Dermatitis, Allergic Contact / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology*; D009783:Dermatitis, Occupational / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D009387:Neoprene / Q000009:adverse effects; D009656:North America / Q000453:epidemiology; D010328:Patch Tests / Q000379:methods; D011237:Predictive Value of Tests; D015995:Prevalence; D012189:Retrospective Studies; D012408:Rubber / Q000009:adverse effects*; D013890:Thiourea / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000737:chemistry
D000485:Allergens; C035318:diethylthiourea; C034546:1,3-dibutyl-2-thiourea; D012408:Rubber; D009387:Neoprene; D013890:Thiourea