Two unusual cases of allergic contact stomatitis caused by methacrylates.

A 57-year-old female presented with facial oedema, cheilitis and stomatitis that started after three overnight applications of the ‘Evolution’TM home tooth-whitening kit. Her symptoms slowly resolved without treatment 3 days after she stopped using the product. The whitening kit includes an individualized plastic dental mould, which is prepared by the dentist, and a whitening gel, which contains 2-hydroxyethylmethacrylate (2-HEMA). 2-HEMA is used to create a gel-like substance and to stabilize the pH, to improve bleaching efficacy. The gel is applied to the mould, and sits in the mouth overnight. Patch testing with the British baseline series and an ‘acrylates’ series was performed, with allergens from Chemotechnique Diagnostics (Vellinge, Sweden) applied in Finn Chambers® (Epitest, Oy, Finland) on Scanpor® tape (Actavis, Vennesla, Norway), according to ICDRG guidelines. Readings at day (D)2 and D4 showed positive (+) reactions to 2-HEMA and ethyleneglycol dimethacrylate on D4.