ABSTRACT
Background: A 29-year-old woman, with personal history of atopy, presented with face and neck dermatitis lasting 6 months. During the past year, she worked as a nurse in a COVID-19-dedicated ward. The dermatitis had developed since she started using FFP2 masks. She referred using three FFP2 masks, with similar symptoms: 3 M© 9320+, Halyard© Fluidshield N95 and PM 2.5©. She also mentioned history of contact-hypersensitivity reactions to metals, green clothes and leather shoes for several years. Physical examination exhibited erythematous plaques distributed along the contact area of the elastic bands of the FFP2 masks. Patch tests revealed delayed hypersensitivity to the elastic bands 3 M© 9320+ and PM 2.5© (++), mercapto mix (++), 2-mercaptobenzothiazole (MBT) (++), 2-(4-morpholinylmercapto)benzothiazol (MOR) (++), N-cyclohexyl-2-benzothiazolesulfenamide (++), textile dye mix Mx-30 (++), disperse yellow 3 (++), disperse blue 106 (+), potassium dichromate (+), cobalt dichloride (+) and nickel sulfate hexahydrate (+). A latex skin prick test was negative. Allergic contact dermatitis (ACD) caused by elastic bands of FFP2 masks (3 M© 9320+ and PM 2.5 ©) was diagnosed. She was prescribed methylprednisolone aceponate 0.1% cream bid during five days and masks were changed to a type with cotton cloth bands, with resolution of the complaints. ACD to FFP2 masks components in health care workers can be severe, given the prolonged and continuous contact with the source of allergens. The rubber additives thiurams and dithiocarbamates are the main allergen groups involved in ACD to rubber bands in FFP2 masks. This seems to be the first report caused by mercaptobenzothiazole.