Patch Testing with a New Composition of Mercapto Mix: A Multicentre Study by the Swedish Contact Dermatitis Research Group
Malin Engfeldt, Marléne Isaksson, Bo Glas, Lina Hagvall, Anna Löfnertz Petersson, Mihály Matura, Berndt Stenberg, Cecilia Svedman, Magnus Bruze
This study investigated whether more patients with contact allergies were detected by patch testing with mercapto mix with a higher concentration of 2-mercaptobenzothiazolinone (MBT) than the commonly used mercapto mix. A total of 3,143 dermatitis patients in 5 Swedish dermatology departments were patch- tested with 3 mercapto test preparations: MBT 2.0% petrolatum (pet.); mercapto mix 2.0% pet.; and mercapto mix 3.5% pet. Positive reactions to these mercapto mixes varied between 0–0.50%, 0–0.93%, and 0–1.4%, respectively, in the 5 centres. Numerically, mercapto mix 3.5% pet. detected all positive patients and more patch-test positive patients than did the 2 other substances, but the difference was not statistically significant. The authors recommend replacing mercapto mix 2.0% pet. in the Swedish baseline series with mercapto mix 3.5% pet., since the latter also detected those patients who would have been missed because MBT 2.0% is not included in the Swedish baseline series.
Mercaptobenzothiazole compounds are used as accelerators in rubber products. These compounds are associated with causing allergic contact dermatitis. Various mercaptobenzothiazole compounds have been tested to find the optimal test substance, both single substances and mixes of mercaptobenzothiazole compounds, for use in patch testing patients. This study compared the results of patch testing 3,143 patients with mercaptobenzothiazole mix 3.5%, mercaptobenzothiazole 2% and mercaptobenzothiazole mix 2% to find out what proportion of allergic individuals were detected with the 3 different mercapto test preparations. Mercaptobenzothiazole mix 3.5% detected all positive patients and detected more patch test positive patients than did the 2 other substances. The authors therefore recommend replacing mercaptobenzothiazole mix 2.0% in the Swedish baseline series with mercaptobenzothiazole mix 3.5%.