Flu, caused by the influenza virus, is a respiratory infection. Children with flu often experience fever, cough, sore throat, nasal congestion or runny nose, fatigue, and body aches. During illness and recovery, respiratory secretions can thicken and change color from clear to white, yellow, or green.

Green phlegm does not automatically indicate a bacterial infection in a child, nor is it a basis for self-medicating with antibiotics. When the respiratory tract is inflamed by a virus, immune cells and accumulated secretions can cause phlegm to change color. Children with viral respiratory illnesses may continue to cough up yellow or green phlegm for some time during recovery.

Antibiotics are effective only against certain bacterial infections; they do not kill the flu virus. Therefore, if a child's fever has decreased, they are alert, eating and drinking well, breathing normally, and their overall symptoms are improving, antibiotics are not necessary.

Dr. Trinh Thi Hong Van examines a child with flu. Photo: Tam Anh General Hospital.

Coughing is the body's mechanism to clear secretions and mucus from the respiratory tract. After acute flu symptoms subside, a child may continue to cough for a period. Parents or caregivers should monitor the progression of symptoms rather than focusing solely on phlegm color. If the child's cough gradually lessens, they are eating and sleeping better, have no recurrent fever, and are not experiencing difficulty breathing, these are typically signs of recovery.

However, flu can predispose children to secondary bacterial infections such as pneumonia, otitis media (middle ear infection), or sinusitis. Parents should be vigilant if a child who was recovering suddenly develops a recurrent fever, a high or prolonged fever, an increasingly severe cough, noticeably increased phlegm, increased fatigue, or poor appetite.

If a child experiences rapid breathing, difficulty breathing, chest indrawing, chest pain, bluish lips, lethargy, or difficulty waking, they should be taken to a medical facility immediately. Doctors will assess for bacterial infection based on the disease progression, symptoms, respiratory examination, and accompanying signs.

Parents should not self-administer antibiotics or reuse prescriptions from previous consultations. Unnecessary antibiotic use does not accelerate flu recovery and can lead to side effects such as diarrhea, vomiting, rash, allergic reactions, and increased risk of antibiotic resistance.

If a child still has a phlegm cough after flu, parents should ensure they drink plenty of fluids to thin secretions, get adequate rest, eat nutritious meals, and perform nasal hygiene if there is congestion or excessive nasal discharge. Do not combine multiple cough suppressants, expectorants, or antibiotics without a doctor's guidance.

If a child's fever has resolved and their health is improving but they still have a green phlegm cough, parents can continue monitoring and follow up as scheduled. Conversely, if the phlegm cough persists without improvement, the child develops a recurrent fever after previously improving, the cough worsens, or they experience difficulty breathing, chest pain, increased fatigue, or a general decline in condition, they should be examined to promptly detect secondary infections and flu complications.

To prevent flu and reduce the risk of severe illness and complications, parents should ensure children receive the flu vaccine from 6 months of age and get annual booster shots as recommended.

Dr. Trinh Thi Hong Van

Department of Pediatrics, Tam Anh General Hospital Ho Chi Minh City