A bitter mouth with a cold may be caused by a dulled sense of taste due to a viral infection, gastrointestinal dysfunction, or taking medication. Colds are usually acute infectious diseases of the respiratory tract caused by viruses, with symptoms such as nasal congestion and runny nose, but also oral mucosal dysfunction. As taste buds are sensitive and easily stimulated, viral infections may cause taste receptors to be unresponsive and glands to secrete less, resulting in symptoms such as dry mouth and bitter taste in the mouth. Colds can also affect digestive function, with poor gastric motility and reduced digestion of food, resulting in symptoms such as bloating and belching. If gastric juice refluxes into the oropharynx, it can make the mouth bitter and tasteless. At the same time, bile may also reflux into the stomach, further aggravating the symptoms of bitter mouth. Taking cold and flu medications, which generally have a bitter taste, can also lead to a bitter mouth. Bitter mouth can also be caused by other diseases. If the symptoms are not relieved or worsened, it is recommended to consult a doctor for a clear diagnosis and reasonable treatment under the doctor’s guidance. Drink plenty of fluids and pay attention to balanced nutrition during cold and flu.