A swollen bag at the corner of the mouth may be a local soft tissue inflammation caused by an infection, especially a bacterial infection, which may result in localized skin redness and swelling, with some burning and pain. Some patients may have a local allergic reaction, and the most common allergy may be giant urticaria, also known as angioneurotic edema, which is generally manifested as edematous bumps, so the appearance may appear bulging, but mostly without pain. This condition may also be caused by mosquito bites, or mite allergies and other factors that lead to local inflammation of allergic reactions, so local swelling may also occur.