Colds that go from clear to thick nasal discharge need to be treated according to the cause. Colds are caused by viruses, and going from clear to thick nasal discharge may be related to causes such as a bacterial infection secondary to a cold, or acute rhinitis. Treatment includes anti-infection treatment and nasal drops. 1. Bacterial infection: Colds secondary to bacterial infection will appear clear to thick nasal mucus, need to give antibiotic treatment such as amoxicillin, cephradine and so on. 2. Combined acute rhinitis: In most cases, colds are combined with acute rhinitis. Acute rhinitis is caused by viral infection, which is often followed by bacterial infection on the basis of viral infection. After the secondary bacterial infection, there will be a change from clear nasal mucus to mucous, mucopurulent or purulent nasal mucus. Topical nasal drops can be used for treatment: hydroxymetazoline hydrochloride nasal drops, 0.5% to 1% (0.5% for children) ephedrine nasal drops (the drug should be used for no more than 7 days in a row), budesonide nasal spray and so on. Systemic treatment is also needed if necessary: if purulent nasal discharge is present, antibiotics can be applied for treatment, such as cefaclor and azithromycin. There may be other reasons for a cold to go from clear to thick nasal discharge, so it is recommended to consult a specialist in time. The above medications should be used in a standardized and reasonable manner under the guidance of a professional physician.