High frequency of false-positive reactions in attempted patch testing with acrylate/methacrylate mixes

Background. Although acrylate/methacrylate allergy has been frequently reported, until now patch testing with this group of allergens has been unwieldy, requiring the application of large supplementary series in most centres. Objectives. To formulate and evaluate two mixes of acrylate/methacrylate allergens in three centres (Malmo, Singapore, and Leuven). Patients/materials/methods. All patients tested with the baseline series during the study period were also patch tested with the mixes. Mix 1 consisted of: triethyleneglycol diacrylate (TREGDA) 0.1% wt/wt, 2-hydroxyethyl methacrylate (2-HEMA) 1.0% wt/wt and ethyleneglycol dimethacrylate 1.0% wt/wt in petrolatum. Mix 2 consisted of: TREGDA 0.1% wt/wt and 2-HEMA 2.0% wt/wt in pet. The separate components of the two mixes were also tested simultaneously. Results. There were 25 (5 males; 20 females) positive reactions to mix 1 with 16 in Malmo, 8 in Singapore, and 1 in Leuven. Positive reactions to mix 2 were seen only in Malmo, in 8 female patients. Thus, the positive reaction rate for mix 1 was 8.3% overall (Malmo 7.7%, Singapore 18.6%, and Leuven 2.1%), and that for mix 2 was 2.7% overall (Malmo 3.8%, Singapore 0%, and Leuven 0%). Of the 16 positive reactions to mix 1 in Malmo, only 4 were considered to be true allergic reactions, as the component allergen testing gave totally negative results in 12/16. For mix 2, only 3/8 positive reactions were considered to be true allergic reactions, as the component testing was negative in 5/8. Many doubtful (10-20%) and positive but non-allergic reactions were recorded, leading to early termination of the study. Conclusions. Although this was an unsuccessful attempt to formulate an acrylate/methacrylate mix, our experience will be useful for those embarking on future attempts to do this.