Diagnosing Chronic Cough

In most children, coughing is a common but temporary symptom of an upper respiratory viral or bacterial infection. Usually a cough goes away within a week or two on its own. But in some children—even in those who are otherwise healthy—a cough can persist for four weeks or longer, causing significant discomfort for the child and understandable concern for parents.

Doctor Examines Pediatric Patient

Through physical exams and other tests, our pulmonologists can diagnose the cause of your child’s chronic cough.

Causes of Chronic Cough in Children

The vast majority of chronic cough in children is due to protracted bacterial bronchitis, a prolonged infection in the bronchial tubes that supply oxygen to the lungs. Protracted bacterial bronchitis occurs when bacteria such as Haemophilus influenza and Streptococcus pneumonia colonize the airways. This condition increases mucus production, which can cause a persistent, phlegmy cough for more than four weeks with no other symptoms.

In recent years, doctors at Hassenfeld Children’s Hospital at NYU Langone have begun to diagnose more people with pertussis, or whooping cough, an infection caused by the bacterium Bordetella pertussis that leads to uncontrollable, violent coughing. Although most children are vaccinated against pertussis, immunization does not completely prevent the infection.

Some children have a type of asthma that causes a dry, chronic cough, which is known as cough-variant asthma. Coughing is usually the only symptom in children with this type of asthma.

Other causes of a chronic cough in children include:

  • Postnasal drip and sinusitis, which sometimes occur in children with allergies
  • Exposure to second-hand smoke
  • Tuberculosis, a bacterial lung infection
  • Serious lung diseases, such as cystic fibrosis
  • Congenital airway and gastrointestinal tract abnormalities, which affect the structure of the lungs or airways and can cause breathing problems

Gastroesophageal reflux disease is a common cause of chronic cough in adults. However, research shows that although this condition can make a cough worse, it is not among the leading causes of chronic cough in children.

Our specialists can diagnose the precise cause of your child’s chronic cough. Our pulmonologists, or lung specialists, begin with a comprehensive physical exam to assess your child’s symptoms, followed by additional tests to check for bacterial infection and to rule out other possible causes.

If needed, our pulmonologists make referrals to other specialists, such as gastroenterologists or infectious disease specialists, who can confirm and treat less common causes of chronic cough in children.

Respiratory Exam

During this exam, a doctor reviews your child’s medical history with you and asks about any respiratory symptoms or previous illnesses. Our doctors are highly skilled in techniques such as observing respiratory movements during breathing and listening with a stethoscope for unusual breathing sounds, such as wheezing or crackling. They may also feel or tap your child’s chest to see if some areas of the lungs are working better than others.

Sputum Culture

In a sputum culture, a doctor takes a sample of your child’s mucus, if enough can be produced from coughing, to look for the presence of a bacterial infection. If bacteria are found in the sputum sample, our pathologists identify the exact type, so that they can select the most effective antibiotic treatment.

Lung Function Tests

Lung function tests play a major role in identifying the cause of a chronic cough and can be performed in children as young as age 5. Depending on the possible cause of the cough, our doctors may perform one or more of the following tests:


Spirometry measures how much and how quickly your child can blow air out of the lungs by breathing into a special mouthpiece. This test may be used to look for signs of asthma.

Bronchodilator Challenge Test

In a bronchodilator challenge test, your child breathes into a spirometer before and after being given a medication, such as albuterol, to open up the airways. The results of this test may be used to confirm a diagnosis of asthma.

Impulse Oscillometry

Impulse oscillometry is used to diagnose asthma in younger children who have difficulty forcing air into a spirometer. In this test, the child breathes normally into a tube that measures resistance to pressure in the airways.

Exercise Challenge

An exercise challenge test, which uses spirometry to measure lung function before and after riding on a stationary bicycle, may be used to look for signs of exercise-induced asthma, which can trigger a chronic cough.


This test may be used when the cause of a chronic cough cannot be determined with a physical exam and sputum culture, or if the cough remains after treatment.

Bronchoscopy is performed in the hospital while your child is under anesthesia. In this procedure, the pulmonologist inserts a bronchoscope—a flexible tube with a camera at its tip—through your child’s nose or mouth and into the airways. Bronchoscopy allows the doctor to see inside your child’s airways and to identify any blockages or damage to the tissue, such as scarring.

Chest X-ray

X-rays provide a picture of the lungs and may be used to rule out unusual causes of a chronic cough, including lung abnormalities that are present at birth.

After our doctors establish the correct diagnosis, the next step is to select the appropriate treatment for your child.

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