Devices and methods are provided for inhibiting mouth breathing and/or improving nasal breathing, e.g., for PAP users or users with other sleeping problems. In an exemplary embodiment, an adhesive device is provided that includes an elongate membrane comprising first and second ends and side edges extending between the first and second ends, a first surface comprising an adhesive layer. The adhesive layer may be a low tack adhesive that is adherent to skin, yet is also easily removable without leaving significant residue. Optionally, the device may include one or more valves to provide one-way flow across the membrane, one or more weakened regions in the membrane, and/or one or more tabs to facilitate removal of the membrane from over a user's mouth.