There is always mucus sputum in the mouth which may be caused by coccidioidal stomatitis, respiratory diseases, etc. The details are as follows. 1. Coccidioidomycosis: acute infectious stomatitis, oral mucosal congestion, localized formation of vesicles or ulcers, which are covered with grayish-white or yellowish-brown pseudomembrane, bloody exudate, patients with increased saliva, saliva and exudate will become sticky after mixing. 2. Respiratory diseases: such as acute bronchitis, chronic bronchitis, pneumonia, bronchial asthma, pharyngitis and other respiratory diseases may lead to mucus sputum. Mucus sputum always in the mouth may have other reasons, it is recommended to go to the hospital in a timely manner, to clarify the cause of the disease for targeted treatment.