Cough is a protective reflex for upper airways. It is one of the most commonly reported symptoms in patients seeking medical advice and accounts for huge sums of expenditures on over-the counter remedies, physicians visits and loss of  time at work for parents.

Acute cough (one lasting less than 3 weeks) is almost always self-limiting and mostly due to viral upper respiratory tract infections (URTI). Nearly all such cough resolve within this time period. However, a cough following an URTI and  persisting for longer than three weeks, is may be termed as “post viral cough”.  Acute cough may arise not only from viral URTI but also from events such as pneumonia, or less commonly aspiration of a foreign body or whooping cough. Acute URTI viral infections exhibit seasonality, although some viruses (eg. rhinovirus) are prevalent throughout the year. Some acute cough symptoms may be associated with mixed viral infections.

Chronic Cough (one lasting longer than 8 weeks) is often viewed as a symptom with little diagnostic or treatment success. Gastro-oesophageal reflux (GOR), and upper airway disorders associated with postnasal drip (rhinitis, rhinosinusitis) may be the cause of prolonged cough.

In young children “cough-variant asthma”( Asthma presenting without wheezing, but only coughing) is rare. Common expert consensus is to investigate children with prolonged chronic cough, particularly if cough persists beyond three months.

Experimental evidence suggests that respiratory viruses can induce changes in airway sensory nerves and promote a series of inflammatory cytokines, leading  to prolonged cough.

A  separate discussion is whether viral infections- which up to 92% of cases present with cough, triggers the onset of asthma/wheezing/cough in childhood. The answer seems complex; exposure to normal environmental bacteria, viruses and worms may help normal maturation of the immune system and may be protective against long term symptoms. However early infant bronchiolitis due to several viruses (mostly RSV, Rhinovirus) may have a separate effect leading to long term wheezing cough and asthma. 

Latest clinical review on Childhood Cough, BMJ; 2012, 344:40-45

Conditions Treated
Respiratory infections
Hay fever/allergic rhinitis
Milk and food allergies
Pollen allergies
Feeding difficulties
Gastroesophageal reflux
Neonatal and early infancy problems