A fever that comes back after three days of cold and flu may be caused by incomplete recovery, reinfection, etc. The solutions include medication, daily care, and so on. 1. Incomplete recovery: In the event of recurrent illness, drugs such as acetaminophen, aspirin and ibuprofen can be used to relieve fever and analgesia. However, it should be noted that these drugs may cause damage to the liver and the mucous membrane of the digestive tract, so pay attention to the dosage of drugs. 2. Reinfection: cold and fever recurrence, it is recommended to do a good job of warmth during the illness, add clothing in a timely manner, at the same time go out to wear a mask, avoid going to crowded places. In addition, be sure to take your medication regularly, and don’t let your guard down just because the symptoms have subsided. Colds may also be accompanied by coughing, runny nose, nasal congestion and other problems, you can use dextromethorphan, paracetamol and other medications for symptomatic treatment, and finally the medication must be thorough, the end of the treatment should be rechecked, to confirm that the disease disappeared, to avoid recurring fever symptoms.