Common colds usually start with a viral infection and typically clear in 1 to 2 weeks. Some people continue to have mucus and cough, which can take up to 8 weeks to clear.
Mucus production and coughing are protective mechanisms of the respiratory airways to expel irritants that come into contact with the airways. Irritants include infections, air pollutants (smoking & haze), allergens (such as dust and animal danders), and other irritants, such as acid from gastric reflux or foreign bodies.
What causes a lingering cough after a common cold?
A lingering cough after a common cold or upper airway infection is also known as post-infective cough, lasting 3 to 8 weeks.
Common causes of post-infective cough include:
Post-nasal drip
- Post-nasal drip refers to mucus dripping from the nasal passages into the throat to cause cough. It tends to be worse when lying down.
Inflammation of the airways.
- Infection can directly cause inflammation or swelling of the airways and would subside over time. People with sensitivity to allergens or asthma tend to have more mucus production and more inflammation or swelling of the airways when they have upper airway infections or common colds. The cough tends to linger till the mucus and swelling subsides. Appropriate medications would be needed for those with asthma and allergic rhinitis.
When should one seek medical attention for the post-infective lingering cough?
Post-infective lingering cough tends to settle 3 to 8 weeks after a cold and tend not to be contagious. The cough settles when the mucus and swelling clear up. Symptoms should not worsen but improve with time. If symptoms worsen, or the cough is affecting sleep or work, or if you have known heart or lung/respiratory (like asthma) conditions, or if there is a cough beyond 6-8 weeks, it is advisable to see your family doctor.
The following symptoms would require earlier or prompt medical attention:
- Wheezing
- Tightness in chest
- Shortness of breath
- Persisting fever
- Night sweats
- Coughing up blood
- Persisting thicker, darker mucus
- Sinus pain
Asthma & infection of the sinuses, lower airways or lungs can occur following initial viral upper airway infection, which would require treatment.
While not as common as viral infections, certain infections, such as Pertussis or Mycoplasma, tend to cause prolonged coughs. Cough can last 1-2 months, and most people recover from mycoplasma infections without antibiotics. Some people may develop chest infections, and antibiotics are usually used to treat chest or lung infections. Pertussis in adults may show up as a persisting cough without the typical ‘whooping’ cough.
Are there remedies for post-infective cough?
Mucus may be yellow or green in the initial few weeks, which is normal and usually would resolve without needing antibiotics. Steam or nasal saline helps clear away mucus, which helps reduce coughing. Throat sprays and lozenges, and in some studies, honey used for children, have helped soothe the throat and reduce the cough.
For individuals who tend to get sensitivity of the nose or eyes to allergens, using antihistamines, nasal saline, and nasal steroids would help reduce the inflammation and mucus production, reducing the duration and severity of the post-infective cough. Individuals with known asthma would need adjustment of their asthma medications to reduce inflammation and cough. Some individuals with heartburn can have a persisting cough; medication to reduce gastric acid or neutralise acid would help to ease irritation to the throat and relieve the cough.
