if you're referring to a crack in the corner of your mouth where the upper and lower lips join you may be suffering from perleche known medically as angular cheilitis. perleche can be caused by a fungal infection in which case you'll need to see a doctor for medication to help it heal. the condition also can be caused by a deficiency of vitamin b so you can try taking a vitamin supplement (assuming you're not allergic to any medications or food colorings) or eating more green leafy vegetables which typically contain plenty of different b vitamins. because of the possibility this is a fungal infection i'd suggest making an appointment with your primary care provider for an evaluation. i wish you all the best!
i have a cut on the corner of my mouth that wont heal. what can i use to help?