The main causes of bitter mouth in cold and flu patients include dry tongue due to fever or gastrointestinal disorders caused by inflammation, etc., which require prompt medical treatment. When a patient has a cold, he or she usually has a fever, and when the tongue becomes dry and the taste buds lose their function, the mouth becomes bitter, and the food becomes tasteless. The bitter mouth of patients with colds is usually related to gastrointestinal disorders. The inflammation that accompanies colds can interfere with the gastrointestinal function of patients, which makes their mouths feel bitter, and they should take more rest time to fight against the disease and recover their bodies.