Adult diphtheria, or diphtheria in adults, is categorized into pharyngeal diphtheria, laryngeal diphtheria, nasal diphtheria, and diphtheria in other parts of the body, and the symptoms of each type of diphtheria are different. 1. Pharyngeal diphtheria: Pharyngeal diphtheria is categorized into common type, light type, heavy type and extremely heavy type according to the severity of the disease. (1) Common type: Common pharyngeal diphtheria has a slow onset, with fever, sore throat, loss of appetite, generalized fatigue, local pharyngeal congestion, enlarged tonsils and other symptoms. Generally, pseudomembrane can appear after 24 hours of illness. (2) Light-type: Light-type pharyngeal diphtheria is mainly characterized by the appearance of pseudomembrane in tonsils, sore throat, often accompanied by fever and other symptoms. (3) Severe and very severe: severe pharyngeal diphtheria has more serious systemic symptoms, such as high fever, nausea, vomiting, and generalized weakness, etc. The pseudomembrane of the diseased area gradually increases in size, and the pseudomembrane appears after 24 hours. The pseudomembrane of the diseased area gradually increases in size, thickening, the color of pseudomembrane becomes gray or yellow, often accompanied by halitosis and other symptoms, and there may be myocarditis, peripheral nerve paralysis and other complications. The very heavy pharyngeal diphtheria fever continues to increase, dyspnea, cyanosis, combined with cardiac arrhythmia, toxic shock, etc., and the severe cases can die. 2. Laryngeal diphtheria: there are symptoms such as hoarseness or loss of voice, dyspnea, barking cough, etc. Clinical symptoms such as nasal agitation, “three-concave” phenomenon and cyanosis can be seen. 3. Nasal diphtheria: mainly nasal congestion, plasma bloody nasal discharge, reddening, erosion, crusting and other symptoms of the skin around the nostrils. 4. Other parts of diphtheria: common vulva, eyes, mouth, ears and other parts of the body, mainly in the diseased parts of the pseudomembrane. Adult diphtheria needs to go to the hospital in time to avoid delaying the condition.