Dry mouth after cold is mainly caused by the involvement of inflammatory factors after viral infection, which makes the mucous membrane of the upper respiratory tract congested and increased secretion, and the secretions in the mouth and oropharynx are evaporated with the breathing movement, and water is lost, which causes dry mouth, and also causes headache, sluggish taste, nasal congestion, and clear water-like nasal discharge. You should hydrate more, drink more water, eat more vegetables and fruits, and also supplement vitamin C. Make sure to drink at least 2000ml of water every day, and make sure to take rest and not to exert yourself during the treatment period.