Bitter lips can be caused by lipitis, oral diseases, or gastrointestinal diseases. 1. Lipitis: the infection of external pathogenic bacteria, or allergic factors caused by lipitis, may cause the lips to have congestion, swelling, exudate, which leads to the symptoms of bitter lips. 2. Oral disease: for example, usually do not pay attention to oral hygiene, or have tooth decay, periodontitis, mouth ulcers, etc. may also lead to the feeling of bitter lips. 3. Gastrointestinal diseases: common bile reflux gastritis, chronic gastritis, cholecystitis and other possibilities, can cause digestive juices reflux to the mouth, thus showing bitter lips. Bitter lips may have other reasons, you need to go to the hospital in time to check, clear cause and follow the doctor’s instructions for treatment.